CMP Journal 2025-02-18
Statistics
Nature: 1
Nature Nanotechnology: 2
Nature Physics: 2
Physical Review Letters: 18
Physical Review X: 1
arXiv: 124
Nature
Vertical structure of an exoplanet's atmospheric jet stream
Original Paper | Atmospheric dynamics | 2025-02-17 19:00 EST
Julia V. Seidel, Bibiana Prinoth, Lorenzo Pino, Leonardo A. dos Santos, Hritam Chakraborty, Vivien Parmentier, Elyar Sedaghati, Joost P. Wardenier, Casper Farret Jentink, Maria Rosa Zapatero Osorio, Romain Allart, David Ehrenreich, Monika Lendl, Giulia Roccetti, Yuri Damasceno, Vincent Bourrier, Jorge Lillo-Box, H. Jens Hoeijmakers, Enric Pallé, Nuno Santos, Alejandro Suárez Mascareño, Sergio G. Sousa, Hugo M. Tabernero, Francesco A. Pepe
Ultra-hot Jupiters, an extreme class of planets not found in our solar system, provide a unique window into atmospheric processes. The extreme temperature contrasts between their day- and night-sides pose a fundamental climate puzzle: how is energy distributed? To address this, we must observe the 3D structure of these atmospheres, particularly their vertical circulation patterns, which can serve as a testbed for advanced Global Circulation Models (GCM) e.g.1. Here we show a dramatic shift in atmospheric circulation in an ultra-hot Jupiter: a unilateral flow from the hot star- facing side to the cooler space-facing side of the planet sits below an equatorial super-rotational jet stream. By resolving the vertical structure of atmospheric dynamics, we move beyond integrated global snapshots of the atmosphere, enabling more accurate identification of flow patterns and allowing for a more nuanced comparison to models. Global Circulation Models based on first principles struggle to replicate the observed circulation pattern3 underscoring a critical gap between theoretical understanding of atmospheric flows and observational evidence. This work serves as a testbed to develop more comprehensive models applicable beyond our Solar System as we prepare for the next generation of giant telescopes.
Atmospheric dynamics, Exoplanets
Nature Nanotechnology
Molecular-scale CO spillover on a dual-site electrocatalyst enhances methanol production from CO2 reduction
Original Paper | Carbon capture and storage | 2025-02-17 19:00 EST
Jing Li, Quansong Zhu, Alvin Chang, Seonjeong Cheon, Yuanzuo Gao, Bo Shang, Huan Li, Conor L. Rooney, Longtao Ren, Zhan Jiang, Yongye Liang, Zhenxing Feng, Shize Yang, L. Robert Baker, Hailiang Wang
Cobalt phthalocyanine (CoPc) is recognized for catalysing electrochemical CO2 reduction into methanol at high Faradaic efficiency but is subject to deactivation. Cobalt tetraaminophthalocyanine (CoPc-NH2) shows improved stability, but its methanol Faradaic efficiency is below 30%. This study addresses these limitations in selectivity, reactivity and stability by rationally designing a dual-site cascade catalyst. Here we quantify the local concentration of CO, a key intermediate of the reaction, near a working CoPc-NH2 catalyst and show that co-loading nickel tetramethoxyphthalocyanine (NiPc-OCH3) with CoPc-NH2 on multiwalled carbon nanotubes increases the generation and local concentration of CO. This dual-site cascade catalyst exhibits substantially higher performance than the original single-site CoPc-NH2/carbon nanotube catalyst, reaching a partial current density of 150 mA cm-2 and a Faradaic efficiency of 50% for methanol production. Kinetic analysis and in situ sum-frequency generation vibrational spectroscopy attribute this notable performance improvement to molecular-scale CO spillover from NiPc-OCH3 sites to methanol-active CoPc-NH2 sites.
Carbon capture and storage, Electrochemistry, Nanoscale materials
Tandem-controlled lysosomal assembly of nanofibres induces pyroptosis for cancer immunotherapy
Original Paper | Drug delivery | 2025-02-17 19:00 EST
Junya Zhang, Yuxuan Hu, Xidan Wen, Zeyue Yang, Ziyi Wang, Zhiyuan Feng, He Bai, Qi Xue, Yinxing Miao, Tian Tian, Peng Zheng, Jingjing Zhang, Jie Li, Ling Qiu, Jing-Juan Xu, Deju Ye
Pyroptosis has emerged as a promising approach for cancer immunotherapy. However, current pyroptosis inducers lack specificity for cancer cells and have a weak antitumour immune response. Here we report a tumour-specific nanoparticle (NP-NH-D5) that activates pyroptosis by disrupting lysosomes for cancer immunotherapy. NP-NH-D5 undergoes negative-to-positive charge reversal and nanoparticle-to-nanofibre transformation within tumour cell lysosomes through tandem response to extracellular matrix metallopeptidase-2 and intracellular reducing agents. The as-formed non-peptide nanofibres efficiently break the lysosomes and trigger gasdermin-D-mediated pyroptosis, leading to strong immunogenic cell death and alleviation of the immunosuppressive tumour microenvironment. In vivo, NP-NH-D5 inhibits orthotopic 4T1 breast tumours, prevents metastasis and recurrence, and prolongs survival without systemic side effects. Furthermore, it greatly enhances the effectiveness of PD-L1 antibody immunotherapy in the 4T1 late-stage lung metastasis and aggressive orthotopic Pan02 pancreatic tumour models. Our research may open pathways for developing stimuli-responsive pyroptosis inducers for precise cancer immunotherapy.
Drug delivery, Supramolecular chemistry
Nature Physics
Local minima in quantum systems
Original Paper | Mathematics and computing | 2025-02-17 19:00 EST
Chi-Fang Chen, Hsin-Yuan Huang, John Preskill, Leo Zhou
Finding ground states of quantum many-body systems is known to be hard for both classical and quantum computers. Consequently, when a quantum system is cooled in a low-temperature thermal bath, the ground state cannot always be found efficiently. Instead, the system may become trapped in a local minimum of the energy. In this work, we study the problem of finding local minima in quantum systems under thermal perturbations. Although local minima are much easier to find than ground states, we show that finding a local minimum is hard on classical computers, even when the task is merely to output a single-qubit observable at any local minimum. By contrast, we prove that a quantum computer can always find a local minimum efficiently using a thermal gradient descent algorithm that mimics natural cooling processes. To establish the classical hardness of finding local minima, we construct a family of two-dimensional Hamiltonians such that any problem solvable by polynomial-time quantum algorithms can be reduced to finding local minima of these Hamiltonians. Therefore, cooling systems to local minima is universal for quantum computation and, assuming that quantum computation is more powerful than classical computation, finding local minima is classically hard but quantumly easy.
Mathematics and computing, Quantum information, Thermodynamics
Wideband electric field quantum sensing via motional Raman transitions
Original Paper | Atomic and molecular interactions with photons | 2025-02-17 19:00 EST
Hao Wu, Grant D. Mitts, Clayton Z. C. Ho, Joshua A. Rabinowitz, Eric R. Hudson
Ultrasensitive detection of the frequency, phase and amplitude of radiofrequency electric fields is crucial for applications in radio communication, cosmology, dark matter searches and high-fidelity qubit control. Quantum harmonic oscillator systems, especially trapped ions, offer high-sensitivity electric field sensing with nanometre spatial resolution but are typically restricted to narrow frequency ranges centred around the motional frequency of the trapped-ion oscillator or the frequency of an optical transition in the ion. Here we present a procedure that enables precise electric field detection over an expanded frequency range. Specifically, we use motional Raman transitions in a single trapped ion to achieve sensitivity across a frequency range over 800 times larger than previous approaches. We show that the method is compatible with both quantum amplification via squeezing and measurement in the Fock basis, allowing a demonstration of performance 3.4(2.0) dB below the standard quantum limit. The approach can be extended to other quantum harmonic oscillator systems, such as superconducting qubit-resonator systems.
Atomic and molecular interactions with photons, Quantum metrology
Physical Review Letters
Efficiently Cooling Quantum Systems with Finite Resources: Insights from Thermodynamic Geometry
Research article | Open quantum systems & decoherence | 2025-02-18 05:00 EST
Philip Taranto, Patryk Lipka-Bartosik, Nayeli A. Rodríguez-Briones, Martí Perarnau-Llobet, Nicolai Friis, Marcus Huber, and Pharnam Bakhshinezhad
Landauer's limit on heat dissipation during information erasure is critical as devices shrink, requiring optimal pure-state preparation to minimize errors. However, Nernst's third law states this demands infinite resources in energy, time, or control complexity. We address the challenge of cooling quantum systems with finite resources. Using Markovian collision models, we explore resource trade-offs and present efficient cooling protocols (that are optimal for qubits) for coherent and incoherent control. Leveraging thermodynamic length, we derive bounds on heat dissipation for swap-based strategies and discuss the limitations of preparing pure states efficiently.
Phys. Rev. Lett. 134, 070401 (2025)
Open quantum systems & decoherence, Quantum correlations, foundations & formalism
Plasmon-Enhanced Direct-Detection Method for Boosted Sub-MeV Dark Matter
Research article | Particle dark matter | 2025-02-18 05:00 EST
Zheng-Liang Liang, Liangliang Su, Lei Wu, and Bin Zhu
A plasmon, a collective mode of electronic excitation in solid-state detectors, provides a novel way to detect light dark matter (DM). In this work, we present the conditions of DM to produce a plasmon resonance, requiring relativistic velocities for light DM, and generalize the collective excitation framework to account for relativistic DM. As a demonstration, we consider the cosmic ray boosted DM and find that the plasmon resonance can be significantly enhanced in the scenario with a light mediator. Utilizing the first data from the SENSEI experiment with the skipper CCDs at SNOLAB, we obtain a new strong limit on the sub-MeV DM-electron scattering cross section.
Phys. Rev. Lett. 134, 071001 (2025)
Particle dark matter, Plasmons, Dark matter detectors
Hunting Dark Matter Lines in the Infrared Background with the James Webb Space Telescope
Research article | Dark matter | 2025-02-18 05:00 EST
Ryan Janish and Elena Pinetti
Measurements made by the JWST observatory could be used to detect photons emitted by the decay of a hypothetical form of dark matter particle known as the axion.
Phys. Rev. Lett. 134, 071002 (2025)
Dark matter, Optical, UV, & IR astronomy, Particle dark matter, Particle decays
Sensitivity of JWST to eV-Scale Decaying Axion Dark Matter
Research article | Axions | 2025-02-18 05:00 EST
Sandip Roy, Carlos Blanco, Christopher Dessert, Anirudh Prabhu, and Tea Temim
Measurements made by the JWST observatory could be used to detect photons emitted by the decay of a hypothetical form of dark matter particle known as the axion.
Phys. Rev. Lett. 134, 071003 (2025)
Axions, Hypothetical particle physics models, Particle astrophysics, Particle dark matter, Particle decays
Magnetic-Induced Force Noise in LISA Pathfinder Free-Falling Test Masses
Research article | Gravitational wave detection | 2025-02-18 05:00 EST
M. Armano et al.
LISA Pathfinder was a mission designed to test key technologies required for gravitational wave detection in space. Magnetically driven forces play a key role in the instrument sensitivity in the low-frequency regime, which corresponds to the measurement band of interest for future space-borne gravitational wave observatories. Magnetically induced forces couple to the test mass motion, introducing a contribution to the relative acceleration noise between the free-falling test masses. In this Letter we present the first complete estimate of this term of the instrument performance model. Our results set the magnetic-induced acceleration noise during the February 2017 noise run of \({0.25}_{- 0.08}^{+0.15}\text{ }\text{ }\mathrm{fm}\text{ }{\mathrm{s}}^{- 2}/\sqrt{\mathrm{Hz}}\) at 1 mHz and \({1.01}_{- 0.24}^{+0.73}\text{ }\text{ }\mathrm{fm}\text{ }{\mathrm{s}}^{- 2}/\sqrt{\mathrm{Hz}}\) at 0.1 mHz. We also discuss how the nonstationarities of the interplanetary magnetic field can affect these values during extreme space weather conditions.
Phys. Rev. Lett. 134, 071401 (2025)
Gravitational wave detection, Gravitational waves, Gravitational wave detectors
Supersymmetric Localization and Nonconformal \(\mathcal{N}=2\) Supersymmetric Yang-Mills Theories in the Perturbative Regime
Field & string theory models & techniques | 2025-02-18 05:00 EST
Marco Billò, Luca Griguolo, and Alessandro Testa
We examine the relation between supersymmetric localization on \({\mathbb{S}}^{4}\) and standard QFT results for nonconformal theories in flat space. Specifically, we consider \(1/2\) BPS circular Wilson loops in four-dimensional \(\mathrm{SU}(N)\) \(\mathcal{N}=2\) supersonic Yang-Mills theories with massless hypermultiplets in an arbitrary representation \(\mathcal{R}\) such that the $$ function is nonvanishing. On \({\mathbb{S}}^{4}\), localization maps this observable into an interacting matrix model. Despite broken conformal symmetry at the quantum level, we show that within a specific regime of validity the matrix model predictions are consistent with perturbation theory in flat space up to order \({g}^{6}\). At this order, the reorganization of Feynman diagrams based on the matrix model potential, which has been widely tested in conformal models, also applies in nonconformal setups and is realized, in perturbative field theory, through highly nontrivial interference mechanisms.
Phys. Rev. Lett. 134, 071601 (2025)
Field & string theory models & techniques, Quantum field theory, Supersymmetric field theories, Supersymmetry, Group theory
All Planar Two-Loop Amplitudes in Maximally Supersymmetric Yang-Mills Theory
Research article | Perturbation theory | 2025-02-18 05:00 EST
Anne Spiering, Matthias Wilhelm, and Chi Zhang (张驰)
We calculate the general planar dual-conformally invariant double-pentagon and pentabox integrals in four dimensions. Concretely, we derive onefold integral representations for these elliptic integrals over polylogarithms of weight three. These integral representations allow us to determine the respective symbols using consistency conditions alone. Together with the previously calculated double-box integral, these integrals suffice to express all two-loop planar scattering amplitudes in maximally supersymmetric Yang-Mills theory in four dimensions---which we thus calculate for any number of particles and any helicity configuration.
Phys. Rev. Lett. 134, 071602 (2025)
Perturbation theory, Quantum field theory, Scattering amplitudes
\(\mathcal{N}=8\) Supergravity from Positivity
Research article | Feynman diagrams | 2025-02-18 05:00 EST
John Joseph M. Carrasco, Alex Edison, Nia Robles Del Pino, and Suna Zekioğlu
The duality between color and kinematics brings many simplifications to the construction of scattering amplitudes. Here, we show that satisfaction of the tree-level Bern-Carrasco-Johansson relations can dramatically simplify loop computations even when the loop-level relations are not explicitly satisfied. We introduce an agglomerative algorithm, color-dual cut tiling, that builds the entire integrand from the simplest on-shell conditions applied to a seed of off-shell integrand information. Specifically, we demonstrate that for two-to-two scattering at three loops in the maximally supersymmetric gauge theory there is sufficient information contained in planar cuts---completely determined by positivity constraints---to generate all of the nonplanar sector. We further make use of the generalized double copy to generate a representation of maximally supersymmetric gravity as a functional of the planar SYM input. We close with comments on generalizations and possible applications of the approach.
Phys. Rev. Lett. 134, 071603 (2025)
Feynman diagrams, Gauge theories, Perturbation theory, Quantum gravity, Scattering amplitudes, Supergravity, Supersymmetric field theories
First Measurement of the Neutron-Emission Probability with a Surrogate Reaction in Inverse Kinematics at a Heavy-Ion Storage Ring
Research article | Gamma-ray strength functions | 2025-02-18 05:00 EST
M. Sguazzin et al.
Neutron-induced reaction cross sections of short-lived nuclei are imperative to understand the origin of heavy elements in stellar nucleosynthesis and for societal applications, but their measurement is extremely complicated due to the radioactivity of the targets involved. One way of overcoming this issue is to combine surrogate reactions with the unique possibilities offered by heavy-ion storage rings. In this work, we describe the first surrogate-reaction experiment in inverse kinematics, which we successfully conducted at the Experimental Storage Ring (ESR) of the GSI/FAIR facility, using the \(^{208}\mathrm{Pb}(p,{p}^{' })\) reaction as a surrogate for neutron capture on \(^{207}\mathrm{Pb}\). Thanks to the outstanding detection efficiencies possible at the ESR, we were able to measure for the first time the neutron-emission probability as a function of the excitation energy of \(^{208}\mathrm{Pb}\). We have used this probability to select different descriptions of the $$-ray strength function and nuclear level density, and provide reliable results for the neutron-induced radiative capture cross section of \(^{207}\mathrm{Pb}\) at energies for which no experimental data exist.
Phys. Rev. Lett. 134, 072501 (2025)
Gamma-ray strength functions, Inelastic scattering reactions, Level densities, Models & methods for nuclear reactions, Nuclear reaction rates, Nuclear reactions, Nucleon induced nuclear reactions, Radiative capture, Storage rings, Thermal & statistical models
Enhanced Laser Cooling of a Mechanical Resonator via Zero-Photon Detection
Research article | Open quantum systems & decoherence | 2025-02-18 05:00 EST
Evan A. Cryer-Jenkins, Kyle D. Major, Jack Clarke, Georg Enzian, Magdalena Szczykulska, Jinglei Zhang, Arjun Gupta, Anthony C. Leung, Harsh Rathee, Andreas Ø. Svela, Anthony K. C. Tan, Almut Beige, Klaus Mølmer, and Michael R. Vanner
Throughout quantum science and technology, measurement is used as a powerful resource for nonlinear operations and quantum state engineering. In particular, single-photon detection is commonly employed for quantum-information applications and tests of fundamental physics. By contrast, and perhaps counterintuitively, measurement of the absence of photons also provides useful information, and offers significant potential for a wide range of new experimental directions. Here, we propose and experimentally demonstrate cooling of a mechanical resonator below its laser-cooled mechanical occupation via zero-photon detection on the anti-Stokes scattered optical field and verify this cooling through heterodyne measurements. Our measurements are well captured by a stochastic master equation and the techniques introduced here open new avenues for cooling, quantum thermodynamics, quantum state engineering, and quantum measurement and control.
Phys. Rev. Lett. 134, 073601 (2025)
Open quantum systems & decoherence, Optomechanics, Quantum control, Quantum measurements, Quantum optics
Topological Pumping of Multifrequency Solitons
Research article | Atomic, optical & lattice clocks | 2025-02-18 05:00 EST
Yaroslav V. Kartashov, Fangwei Ye, and Vladimir V. Konotop
We report on the topological pumping of quadratic optical solitons, observed through their quantized transport in a dynamic optical potential. A distinctive feature of this system is that the two fields with different frequencies, which together form the quadratic soliton, evolve in separate yet topologically equivalent dynamic optical potentials. Pumping in this system exhibits several notable differences from pumping in cubic media. While Chern indices characterizing quantized transport for uncoupled fundamental and second harmonic waves are nonzero, small-amplitude solitons with narrow spectra do not move, thus revealing a nontopological phase. As the nonlinearity increases, the system undergoes a sharp transition, depending on the velocity of one of the sublattices forming dynamical potential, into the phase where the quantized transport of quadratic solitons governed by nonzero Chern numbers is observed. The power level at which this transition occurs increases with increase of pumping velocity, and the transition is observed even in the regime when the adiabatic approximation no longer applies. Unlike in cubic media, in a quadratic medium neither breakup of topological pumping nor fractional pumping at high power levels are observed.
Phys. Rev. Lett. 134, 073801 (2025)
Atomic, optical & lattice clocks, Nonlinear waves
Vortex Interference Enables Optimal 3D Interferometric Nanoscopy
Research article | Optical microscopy | 2025-02-18 05:00 EST
Wei Wang, Zengxin Huang, Yilin Wang, Hangfeng Li, and Pakorn Kanchanawong
Super-resolution imaging methods that combine interferometric axial (z) analysis with single-molecule localization microscopy (iSMLM) have achieved ultrahigh 3D precision and contributed to the elucidation of important biological ultrastructures. However, their dependence on imaging multiple phase-shifted output channels necessitates complex instrumentation and operation. To solve this problem, we develop an interferometric superresolution microscope capable of optimal direct axial nanoscopy, termed VILM (Vortex Interference Localization Microscopy). Using a pair of vortex phase plates with opposite orientation for each dual-opposed objective lens, the detection point-spread functions (PSFs) adopt a bilobed profile whose rotation encodes the axial position. Thus, direct 3D single-molecule coordinate determination can be achieved with a single output image. By reducing the number of output channels to as few as one and utilizing a simple \(50\mathbin: 50\) beam splitter, the imaging system is significantly streamlined, while the optimal iSMLM imaging performance is retained, with axial precision 2 times better than the lateral. The capability of VILM is demonstrated by resolving the architecture of microtubules and probing the organization of tyrosine-phosphorylated signaling proteins in integrin-based cell adhesions.
Phys. Rev. Lett. 134, 073802 (2025)
Optical microscopy, Optical nanoscopy, Super-resolution techniques
Theory of Pressure Dependence of Superconductivity in Bilayer Nickelate \({\mathrm{La}}_{3}{\mathrm{Ni}}_{2}{\mathrm{O}}_{7}\)
Research article | Pairing mechanisms | 2025-02-18 05:00 EST
Kai-Yue Jiang, Yu-Han Cao, Qing-Geng Yang, Hong-Yan Lu, and Qiang-Hua Wang
A recent experiment showed the superconducting transition temperature in the Ruddlesden-Popper bilayer \({\mathrm{La}}_{3}{\mathrm{Ni}}_{2}{\mathrm{O}}_{7}\) decreases monotonically with increasing pressure above 14 GPa. In order to unravel the underlying mechanism for this unusual dependence, we performed theoretical investigations by combining the density functional theory (DFT) and the unbiased functional renormalization group (FRG). Our DFT calculations show that the Fermi pockets are essentially unchanged with increasing pressure (above 14 GPa), but the bandwidth is enlarged, and particularly the interlayer hopping integral between the nickel \(3{d}_{3{z}^{2}- {r}^{2}}\) orbitals is enhanced. From the DFT band structure, we construct the bilayer tight-binding model in terms of the nickel \(3{d}_{3{z}^{2}- {r}^{2}}\) and \(3{d}_{ {x}^{2}- {y}^{2}}\) orbitals. On this basis, we investigate the superconductivity induced by correlation effects by FRG calculations. We find consistently \({s}_{\pm{}}\)-wave pairing triggered by spin fluctuations, but the latter are weakened by pressure and lead to a decreasing transition temperature versus pressure, in qualitative agreement with the experiment. We emphasize that the itinerancy of the \(d\) orbitals is important and captured naturally in our FRG calculations, and we argue that the unusual pressure dependence would be unnatural, if not impossible, in the otherwise local-moment picture of the nickel \(d\) orbitals. This sheds light on the pertinent microscopic description, and more importantly the mechanism, of superconductivity in \({\mathrm{La}}_{3}{\mathrm{Ni}}_{2}{\mathrm{O}}_{7}\).
Phys. Rev. Lett. 134, 076001 (2025)
Pairing mechanisms, Superconducting order parameter, Unconventional superconductors, Density functional calculations, Functional renormalization group
Absence of Weak Localization on Negative Curvature Surfaces
Research article | Anderson localization | 2025-02-18 05:00 EST
Jonathan B. Curtis, Prineha Narang, and Victor Galitski
The interplay between disorder and quantum interference leads to a wide variety of physical phenomena including celebrated Anderson localization---the complete absence of diffusive transport due to quantum interference between different particle trajectories. In two dimensions, any amount of disorder is thought to induce localization of all states at long enough length scales. In this Letter, we present an argument providing a mechanism for disrupting localization: by tuning the underlying curvature of the manifold on which diffusion takes place. We show that negative curvature manifolds contain a natural infrared cutoff for the probability of self-returning paths. We calculate the Cooperon---directly related to the weak-localization corrections to the conductivity---in hyperbolic space. It is shown that negative curvature leads to a rapid growth in the number of available trajectories a particle can coherently traverse in a given time, reducing the importance of interference effects and restoring diffusive behavior even in the absence of inelastic collisions. We further argue that on certain manifolds with variable curvature the hyperbolic regions dominate due to intermittency and arrest weak localization, which may be of relevance to two-dimensional materials due to surface roughness. This result may be amenable to experimental verification through the use of quantum simulators. Finally, we use results on mixed-curvature gravity by Zel'dovich to argue that our generic result on the absence of weak localization in two dimensions also applies to surfaces of mixed curvature, which may be of relevance to realistic experiments on weakly disordered metallic films on rough substrates.
Phys. Rev. Lett. 134, 076301 (2025)
Anderson localization, Diffusion, Geometric & topological phases, Quantum fields in curved spacetime, Quantum simulation, Random walks, Weak localization, Disordered systems
Continuous Transition between Bosonic Fractional Chern Insulator and Superfluid
Research article | Chern insulators | 2025-02-18 05:00 EST
Hongyu Lu, Han-Qing Wu, Bin-Bin Chen, and Zi Yang Meng
The properties of fractional Chern insulator (FCI) phases and the phase transitions between FCIs and Mott insulators in bosonic systems are well studied. The continuous transitions between FCI and superfluids (SFs), however, despite the inspiring field theoretical predictions [M. Barkeshli and J. McGreevy, Phys. Rev. B 89, 235116 (2014); M. Barkeshli and J. McGreevy, Phys. Rev. B 86, 075136 (2012); M. Barkeshli et al., Phys. Rev. Lett. 115, 026802 (2015); X.-Y. Song et al., Phys. Rev. B 109, 085143 (2024); and X.-Y. Song and Y.-H. Zhang, SciPost Phys. 15, 215 (2023)], have not been directly verified. The existing numerical results of the FCI-SF transition are either indirect or clearly first order. Here, by simply tuning the bandwidth of the Haldane honeycomb lattice model, we find direct transitions from a bosonic FCI at \(\nu =1/2\) filling of a flat Chern band to two SF states with bosons condensed at momenta \(M\) or \(\mathrm{\Gamma }\), respectively. While the \(\mathrm{FCI}\text{- }\mathrm{SF}(M)\) transition is first order, the \(\mathrm{FCI}\text{- }\mathrm{SF}(\mathrm{\Gamma })\) transition is found to be continuous, and the bipartite entanglement entropy at the critical point with the area-law scaling is consistent with the critical theories. Through finite-size criticality analysis, the obtained critical exponents \(\beta \approx 0.35(5)\) and \(\nu \approx 0.62(12)\) are both compatible with those of the 3D \(XY\) universality class within numerical uncertainty and possibly more exotic beyond-Landau ones. This Letter thence presents a direct numerical demonstration of a continuous FCI-SF transition between a topologically ordered phase and a spontaneous continuous symmetry-breaking phase, and further indicates the zero-field bosonic FCI might be realized from a SF state by gradually flattening the dispersion of the Chern band, through the (quasi)adiabatic preparation in ultracold atom systems.
Phys. Rev. Lett. 134, 076601 (2025)
Chern insulators, Fractional quantum Hall effect, Phase transitions, Quantum criticality, Quantum phase transitions, Bose-Einstein condensates, Ultracold gases
Evidence of Athermal Metastable Phase in a Halide Perovskite: Optically Tracked Thermal-Breach Memory
Research article | Phase transitions | 2025-02-18 05:00 EST
Kingshuk Mukhuti, Satyaki Kundu, Debasmita Pariari, Deepesh Kalauni, Ashutosh Mohanty, Aniket Bajaj, D. D. Sarma, and Bhavtosh Bansal
Halide perovskite materials have been extensively studied in the last decade because of their impressive optoelectronic properties. However, their one characteristic that is uncommon for semiconductors is that many undergo thermally induced structural phase transitions. The transition is hysteretic, with the hysteresis window marking the boundary of the metastable phase. We have discovered that in methylammonium lead iodide, this hysteretic metastable phase is athermal, meaning it shows almost no temporal phase evolution under isothermal conditions. We also show that a large number of distinguishable metastable states can be prepared following different thermal pathways. Furthermore, under a reversible thermal perturbation, the states in the metastable phase either show return-point memory or undergo a systematic nonrecoverable phase evolution, depending on the thermal history and the sign of the temperature perturbation. Since the phase fraction can be probed with extreme sensitivity via luminescence, we have an optically retrievable memory that reliably records any breach in temperature stability. Such thermal-breach memory in athermal martensites, of which there are numerous examples, may be useful for tagging packages requiring strict temperature control during transportation or preservation.
Phys. Rev. Lett. 134, 076901 (2025)
Phase transitions, Complex materials, Hybrid perovskites, Semiconductors, Photoluminescence, X-ray diffraction
Detecting Directional Coupling in Network Dynamical Systems via Kalman's Observability
Research article | Collective dynamics | 2025-02-18 05:00 EST
Rayan Succar and Maurizio Porfiri
Detecting coupling in network dynamical systems from time series is an open problem in the physics of complex systems. In this Letter, we tackle this issue from a control-theoretic perspective. Drawing inspiration from Kalman's notion of observability, we argue the presence of directional coupling between two units, \(\text{X}\rightarrow \text{Y}\), when \(\text{X}\) is detected as an internal state from the measurement of \(\text{Y}\). We illustrate this approach on a series of analytically tractable systems, showcasing how it overcomes limitations of state-of-the-art methods for network inference.
Phys. Rev. Lett. 134, 077401 (2025)
Collective dynamics, Deterministic networks, Directed networks, Stochastic dynamical systems, Network inference
Comment on ''Can Neural Quantum States Learn Volume-Law Ground States?''
Article commentary | | 2025-02-18 05:00 EST
Zakari Denis, Alessandro Sinibaldi, and Giuseppe Carleo
Phys. Rev. Lett. 134, 079701 (2025)
Physical Review X
Observation of Quantum Thermalization Restricted to Hilbert Space Fragments and \({\mathbb{Z}}_{2k}\) Scars
Research article | Quantum simulation | 2025-02-18 05:00 EST
Luheng Zhao, Prithvi Raj Datla, Weikun Tian, Mohammad Mujahid Aliyu, and Huanqian Loh
In an out-of-equilibrium Rydberg atom array, chosen subsets of atoms freeze in their initial state, while the rest thermalize, a finding that probes an exotic form of quantum thermalization.
Phys. Rev. X 15, 011035 (2025)
Quantum simulation, Quantum statistical mechanics, Rydberg atoms & molecules, Optical tweezers
arXiv
Incorporation of physics-based strengthening coefficients into phenomenological crystal plasticity models
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
The efforts associated with parametrization of continuum-based models for crystal plasticity are a significant obstacle for the routine use of these models in materials science and engineering. While phenomenological constitutive descriptions are attractive due to their small number of adjustable parameters, the lack of physical meaning of their parameters counteracts this advantage to some extent. This study shows that interaction/strengthening coefficients determined with the help of discrete dislocation dynamics simulations for use in physics-based formulations can also be used to improve the predictive quality of phenomenological models. Since the values of these parameters have been determined for most technologically relevant materials, the findings enable to improve the parametrization of phenomenological crystal plasticity models at no costs.
Materials Science (cond-mat.mtrl-sci)
12 pages, 4 figures. Submitted to "Advanced Engineering Materials"
Tentaclelike spectra and bound states in Hatano-Nelson chain with long-range impurity coupling
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-02-18 20:00 EST
In non-Hermitian systems, the energy spectra and eigenstates exhibit high sensitivity to boundary conditions, lattice geometries, and local impurities. In this paper, we study the effect of long-range impurity coupling, located far from the boundaries, on the paradigmatic non-Hermitian Hatano-Nelson model. Through exact analytical treatment, we reveal the intriguing tentacle-like spectral structures that emerge from the otherwise Bloch or non-Bloch spectra under periodic or open boundary conditions, respectively. We show that these spectral tentacles are associated with emergent bound states near the impurity, with their number determined by the coupling range. We further determine the localization length of these tentacled states using the transfer matrix. Our work indicates that the long-range impurity coupling cannot be treated as a mere perturbative effect and holds promise for state manipulations in non-Hermitian systems.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
Making sense of negative probabilities: An exact representation of the dynamics of quantum spin chains as classical stochastic processes with particle/antiparticle pairs
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-18 20:00 EST
Since the advent of quantum mechanics, classical probability interpretations have faced significant challenges. A notable issue arises with the emergence of negative probabilities when attempting to define the joint probability of non-commutative observables. In this work, we propose a resolution to this dilemma by introducing an exact representation of the dynamics of quantum spin chains using classical continuous-time Markov chains (CTMCs). These CTMCs effectively model the creation, annihilation, and propagation of pairs of classical particles and antiparticles. The quantum dynamics then emerges by averaging over various realizations of this classical process.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
5 pages, 3 figures
Thermal and thermoelectric transport in flat bands with non-trivial quantum geometry
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Kevin Wen, Hong-Yi Xie, Assa Auerbach, Bruno Uchoa
Although quasiparticles in flat bands have zero group velocity, they can display an anomalous velocity due to the quantum geometry. We address the thermal and thermoelectric transport in flat bands in the clean limit with a small amount of broadening due to inelastic scattering. We derive general Kubo formulas for flat bands in the DC limit up to linear order in the broadening and extract expressions for the thermal conductivity, the Seebeck and Nernst coefficients. We show that the Seebeck coefficient for flat Chern bands is topological up to second order corrections in the broadening. We identify thermal and thermoelectric transport signatures for two generic flat Chern bands and also for the generalized flattened Lieb model, which describes a family of three equally spaced flat Chern bands where the middle one is topologically trivial. Finally, we address the saturation of the quantum metric lower bound for a general family of Hamiltonians with an arbitrary number of flat Chern bands corresponding to SU(2) coherent states. We find that only the extremal bands in this class of Hamiltonians saturate the bound, provided that the momentum dependence of their Hamiltonians is described by a meromorphic function.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Si-compatible topological and infrared materials: the promise of Low-Sn GeSn digital alloys
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Yunfan Liang, Damien West, Shunda Chen, Jifeng Liu, Tianshu Li, Shengbai Zhang
Recently, GeSn alloys have attracted much interest for direct-gap infrared photonics and as potential topological materials which are compatible with the semiconductor industry. However, for photonics, the high-Sn content required leads to low detectivity, associated with poor material quality, and the (>35%) Sn required for topological properties have been out of reach experimentally. Here, we demonstrate that by patterning the Sn distribution within Ge, the electronic properties have a far greater tunability than is possible with the random alloy. For the GeSn -digital alloy (DA) formed by confining Sn atoms in atomic layer(s) along the [111] direction of Ge, we show that ~10% Sn can lead to a triple-point semimetal. These findings are understood in terms of Sn ordering causing spatial separation of Sn and Ge band edges, leading to band inversion. This mechanism can also lead to a weak topological insulator, Weyl semimetal, and enables tunable direct bandgaps down to 2 meV, covering the entire infrared range. Our findings are generally applicable to other semiconductors DAs and point to a new class of currently unexplored topological systems accessible by epitaxy and establish the promise of low-Sn GeSn DAs for application as infrared laser diodes and photodetectors in Si photonic integrated circuits and infrared image sensors.
Materials Science (cond-mat.mtrl-sci)
Ultrafast Charge Separation on the Nanoscale Induced by a Uniform Field
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Jan-Philip Joost, Michael Bonitz
When illuminated by white light, atoms, molecules, and materials absorb only certain characteristic energy contributions based on their absorption properties. Here, we show that this effect can be translated from energy to space: a spatially uniform laser pulse can create strongly localized carrier excitations, including excitons, and spatial charge separation on the sub-nanometer scale within a few femtoseconds, opening new avenues for nanoelectronics and bringing petahertz switching within reach. Using nonequilibrium Green functions simulations we demonstrate this effect by exciting targeted areas of small graphene nanoribbon heterostructures by careful choice of the laser energy and polarization.
Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 4 figures
Controlling phase selection, preferred orientation and epitaxy in molybdenum oxide films on mica and sapphire with oxygen content
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Faezeh A.F. Lahiji, Biplab Paul, Ganpati Ramanath, Arnaud le Febvrier, Per Eklund
Molybdenum oxide films are attractive for diverse applications due to properties offered by multiple phases and polymorphs, which also makes exclusive synthesis of desired phases a major challenge. Here, we demonstrate that oxygen flow ratio pO2 is key to phase selection, the type and extent of preferred orientation and epitaxy. Exclusive formation of non-layered monoclinic MoO2 crystals is supported on both mica and sapphire substrates at 500 °C within much of the 0.1 pO2 range, outside which the films are amorphous. At 400 °C, the behavior is qualitatively similar, except for layered orthorhombic MoO3 formation at high pO2 and greater sensitivity of phase selection to pO2 due to the presence of a larger number of other phases. Increasing the pO2 tends to enhance preferred orientation and epitaxy, with fine-grained petal-like microstructure forming at low pO2, and large thin-sheeted crystals for at high pO2; however, MoO2 grows epitaxially on both f-mica and c-sapphire substrates while layered -MoO3 grows epitaxially on f- mica but not on sapphire These findings should facilitate the rationale synthesis of MoOx thin films with control over preferred orientation and microstructure to access and tune properties for applications. The research highlights the critical role of control over deposition parameters in tailoring the properties of MoOx films for applications such as electrochromic coatings and gas sensing.
Materials Science (cond-mat.mtrl-sci)
Topological frustration in twisted, elastic ribbons
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-18 20:00 EST
Carlos E. Moguel-Lehmer, Christian D. Santangelo
Topology is an important determinant of the behavior of a great number of condensed-matter systems, but until recently has played a minor role in elasticity. We develop a theory for the deformations of a class of twisted non-Euclidean sheets which have a symmetry based on the celebrated Bonnet isometry. We show that non-orientability is an obstruction to realizing the symmetry globally, and induces a geometric phase that captures a memory analogous to a previously identified one in 2D metamaterials. However, we show that some of the orientable ribbons also obstruct realizing the symmetry globally. This new obstruction is mediated by the complex interplay between strain, geometry, and topology.
Soft Condensed Matter (cond-mat.soft)
5 pages, 4 figures
van der Waals epitaxy of α-MoO3 films on f-mica by pulsed sputter deposition
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Faezeh A. F. Lahiji, Biplab Paul, Arnaud le Febvrier, Ganpati Ramanath, Per Eklund
This study examines the growth characteristics and structural properties of {}-MoO3 thin films with thicknesses ranging from 2.5 to 160 nm, deposited on f-mica and c-sapphire substrates at 400 °C. X-ray diffraction analysis reveals that the films are predominantly orthorhombic {}-MoO3 with a preferred 0k0 orientation along the out-of-plane direction on both substrates. The d-spacing for the 060 reflection shows a slight reduction with increased thickness, particularly on f-mica, which suggests minimal out-of-plane strain in the film and a stabilization of lattice parametes over larger thicknesses. Furthermore, full-width at half maximum measurements indicate improved stacking and crystal quality on f-mica compared to c-sapphire. The films on f-mica exhibit epitaxial growth with specific orientation relationships, while films on c-sapphire display a fiber texture. The near- thickness-independent nature of the peak positions on f-mica suggests stable lattice parameters and reduced strain accumulation, could be attributed to the van der Waals epitaxy. These results highlight the role of substrate choice in {}-MoO3 film growth and minimizing strain, providing valuable insights into the tuning of thin-film properties.
Materials Science (cond-mat.mtrl-sci)
Shape Changes of Liquid Crystal Elastomers Swollen by Low Molecular Weight Liquid Crystal Drops
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-18 20:00 EST
Mahesha Kodithuwakku Arachchige, Rohan Dharmarathna, Paul Fleischer, Antal Jakli
An elastomer swelling actuator deforms by absorbing a fluid, thus generating mechanical movement. We show that depositing small droplets of low molecular weight liquid crystal on liquid crystal elastomer (LCE) films leads to shape changes and bending actuation. It is found that the radially symmetric LCE director alignments provide radially symmetric hat shapes, while swelling LCEs with uniform director structure leads to arch shapes. Hybrid samples (different director alignments on two sides) lead to more complicated bent shapes. All the observed shapes can be explained by the diffusion that mainly progresses along the direction normal to the director of the LCE. The swelling induced bending force is elevating the top of the swollen LCE up to a factor of 30, providing a powerful and long-lasting actuation. These observations may lead to applications in various fields, like sealants, soft robotics and biomedical devices.
Soft Condensed Matter (cond-mat.soft)
21 pages, 12 figures
Behavior of Ising spins and ecological oscillators on dynamically rewired small world networks
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-18 20:00 EST
Davi Arrais Nobre, Karen C. Abbott, Jonathan Machta, Alan Hastings
Many ecological populations are known to display a cyclic behavior with period 2. Previous work has shown that when a metapopulation (group of coupled populations) with such dynamics is allowed to interact via nearest neighbor dispersal in two dimensions, it undergoes a phase transition from disordered (spatially asynchronous) to ordered (spatially synchronous) that falls under the 2-D Ising universality class. While nearest neighbor dispersal may satisfactorily describe how most individuals migrate between habitats, we should expect a small fraction of individuals to venture on a journey to further locations. We model this behavior by considering ecological oscillators on dynamically rewired small-world networks, in which at each time step a fraction \(p\) of the nearest neighbor interactions is replaced by a new interaction with a random node on the network. We measure how this connectivity change affects the critical point for synchronizing ecological oscillators. Our results indicate that increasing the amount of long-range interaction (increasing \(p\)) favors the ordered regime, but the presence of memory in ecological oscillators leads to quantitative differences in how much long-range dispersal is needed to order the network, relative to an analogous network of Ising spins. We also show that, even for very small values of \(p\), the phase transition falls into the mean-field universality class, and argue that ecosystems where dispersal can occasionally happen across the system's length scale will display a phase transition in the mean-field universality class.
Statistical Mechanics (cond-mat.stat-mech)
Quasi-Large Hole Polarons in BiVO4-Implications for Photocatalysis and Solar Energy Conversion
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Bismuth vanadate (BiVO4 BVO) is a promising photocatalyst for solar energy conversion, but its efficiency is limited by small polaron formation. However, some physical properties of BVO deviate from typical small polaron behavior. Using the state-of-the-art first-principles calculations, we demonstrate that BVO forms a quasi-large hole polaron with a radius around 2 nm, resembling free carriers with high mobility. This polaron is stabilized primarily by acoustic phonon modes, creating a shallow trap state near the valence band maximum, which prolongs its lifetime. Simultaneously, it retains a redox potential comparable to that of free carriers. We propose that such large polarons explain the superior properties of BVO and other transition metal oxide photocatalysts. Tuning phonon modes to stabilize large polarons offers a promising strategy for designing materials with enhanced solar energy conversion efficiency.
Materials Science (cond-mat.mtrl-sci)
Analysis of adiabatic shear coupled to ductile fracture and melting in viscoplastic metals
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Material failure by adiabatic shear is analyzed in viscoplastic metals that can demonstrate up to three distinct softening mechanisms: thermal softening, ductile fracture, and melting. An analytical framework is constructed for studying simple shear deformation with superposed static pressure. A continuum power-law viscoplastic formulation is coupled to a ductile damage model and a solid-liquid phase transition model in a thermodynamically consistent manner. Criteria for localization to a band of infinite shear strain are discussed. An analytical-numerical method for determining the critical average shear strain for localization and commensurate stress decay is devised. Averaged results for a high-strength steel agree reasonably well with experimental dynamic torsion data. Calculations probe possible effects of ductile fracture and melting on shear banding, and vice-versa, including influences of cohesive energy, equilibrium melting temperature, and initial defects. A threshold energy density for localization onset is positively correlated to critical strain and inversely correlated to initial defect severity. Tensile pressure accelerates damage softening and increases defect sensitivity, promoting shear failure. In the present steel, melting is precluded by ductile fracture for loading conditions and material properties within realistic protocols. If heat conduction, fracture, and damage softening are artificially suppressed, melting is confined to a narrow region in the core of the band.
Materials Science (cond-mat.mtrl-sci)
36 pages, 8 figures
An attention-based neural ordinary differential equation framework for modeling inelastic processes
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
To preserve strictly conservative behavior as well as model the variety of dissipative behavior dis- played by solid materials, we propose a significant enhancement to the internal state variable-neural ordinary differential equation (ISV-NODE) framework. In this data-driven, physics-constrained modeling framework internal states are inferred rather than prescribed. The ISV-NODE consists of: (a) a stress model dependent, on observable deformation and inferred internal state, and (b) a model of the evolution of the internal states. The enhancements to ISV-NODE proposed in this work are multifold: (a) a partially input convex neural network stress potential provides polyconvexity in terms of observed strain and inferred state, and (b) an internal state flow model uses common latent features to inform novel attention-based gating and drives the flow of internal state only in dissipative regimes. We demonstrated that this architecture can accurately model dissipative and conservative behavior across an isotropic, isothermal elastic-viscoelastic-elastoplastic spectrum with three exemplars.
Materials Science (cond-mat.mtrl-sci)
20 pages, 8 figures
Thermal response functions and second sound in single-layer hexagonal boron nitride
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-18 20:00 EST
Patrick K. Schelling, Antonio Martinez Margolles, Logan Echazabal
Ballistic heat transport and second sound propagation in solids is of direct relevance in electronic and energy applications at short length scales and low temperatures. Measurement or calculation of thermal conductivity, which is typically a primary objective, may be of limited usefulness for predicting heat transport which does not follow the heat-diffusion equation. In this paper, molecular-dynamics simulations of hexagonal BN (h-BN) are used to compute thermal response functions from equilibrium correlation functions defined in Fourier space. The response functions are useful for describing the time-dependent transport beyond the usual assumptions of Fourier's law. The results demonstrate that for length scales ~110nm at T=100K second sound should be experimentally observable. At higher temperatures and longer length scales, while second sound may not be directly observable, thermal transport can nevertheless strongly deviate from predictions based on the heat-diffusion equation. Along with classical simulations, we outline a first-principles, many-body theoretical approach for calculation of the response function based on solutions of the Bethe-Salpeter equation. The relevant expressions for heat current clarify the importance of phase coherence within a phonon branch to the observation of second sound. Previous work on one-dimensional chains is also discussed to show that materials characterized by linear dispersion and simple phonon band structure should more readily display second sound.
Statistical Mechanics (cond-mat.stat-mech), Materials Science (cond-mat.mtrl-sci)
27 pages, 11 figures, to be submitted to Phys. Rev. B
Thermal Stability of Skyrmion Tubes in Nanostructured Cuboids
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Jiang Jailiang, Tang Jin, Bai Tian, Wu Yaodong, Qin Jiazhuan, Xia Weixing, Chen Renjie, Yan Aru, Wang Shouguo, Tian Mingliang, Du Haifeng
Magnetic skyrmions in bulk materials are typically regarded as two-dimensional structures. However, they also exhibit three-dimensional configurations, known as skyrmion tubes, which elongate and extend in-depth. Understanding the configurations and stabilization mechanism of skyrmion tubes is crucial for the development of advanced spintronic devices. However, the generation and annihilation of skyrmion tubes in confined geometries are still rarely reported. Here, we present direct imaging of skyrmion tubes in nanostructured cuboids of a chiral magnet FeGe using Lorentz transmission electronic microscopy (TEM), while applying an in-plane magnetic field. It is observed that skyrmion tubes stabilize in a narrow field-temperature region near the Curie temperature (Tc). Through a field cooling process, metastable skyrmion tubes can exist in a larger region of the field-temperature diagram. Combining these experimental findings with micromagnetic simulations, we attribute these phenomena to energy differences and thermal fluctuations. Our results could promote topological spintronic devices based on skyrmion tubes.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
Published in Nano Lett. 2024, 24, 5, 1587-1593
Beyond the Drude model: surface and non-local effects in near-field radiative heat transfer and the Casimir puzzle
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
We study the charge and current response functions \(P\) and \(\Pi\) in a semi-infinite metal block using the electron surface Green's functions. The surface electrons behave similarly to a two-dimensional Fermi gas but are strongly damped due to coupling to the bulk. This substantially reduces the region of validity of the Drude model for \(P\), which requires the frequency \(\omega \gg \max( v_F q, 1/\tau)\), here \(v_F\) is the Fermi velocity, \(q\) is the wavevector and \(\tau\) is an effective relaxation time. As a consequence, for typical metal in near-field heat transfer, the Coulomb interaction goes as \(1/d^4\) with the distance of the vacuum gap instead of the well-known \(1/d^2\) of Drude model result. The current response \(\Pi\) is shown to be highly anisotropic. The Drude model describes well the transverse directions parallel to the surface but is very different in the normal direction up to about 100 lattice sites away from the surface. These ideas and the residue diamagnetic effect of a nonzero \(\Pi\) on the surface at zero frequency still cannot resolve the Casimir puzzle.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
12 pages 7 figures
Multi-Carrier Thermal Transport in Electronic and Energy Conversion Devices
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Te-Huan Liu, Tianyu Wang, Jun Zhou, Xin Qian, Ronggui Yang
Nonequilibrium multi-carrier thermal transport is essential for both scientific research and technological applications in electronic, spintronic, and energy conversion devices. This article reviews the fundamentals of phonon, electron, spin, and ion transport driven by temperature gradients in solid-state and soft condensed matters, and the microscopic interactions between energy/charge carriers that can be leveraged for manipulating electrical and thermal transport in energy conversion devices, such as electron-phonon coupling, spin-phonon interaction, and ion-solvent interactions, etc. In coupled electron-phonon transport, we discuss the basics of electron-phonon interactions and their effects on phonon dynamics, thermalization, and nonequilibrium thermal transport. For the phonon-spin interaction, nonequilibrium transport formulation is introduced first, followed by the physics of spin thermoelectric effect and strategies to manipulate them. Contributions to thermal conductivity from magnons as heat carriers are also reviewed. For coupled transport of heat and ions/molecules, we highlight the importance of local molecular configurations that determine the magnitude of the electrochemical gradient, which is the key to improving the efficiency of low-grade heat energy conversion.
Materials Science (cond-mat.mtrl-sci)
Percolation in a three-dimensional non-symmetric multi-color loop model
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-18 20:00 EST
Soumya Kanti Ganguly, Sumanta Mukherjee, Chandan Dasgupta
We conducted Monte Carlo simulations to analyze the percolation transition of a non-symmetric loop model on a regular three-dimensional lattice. We calculated the critical exponents for the percolation transition of this model. The percolation transition occurs at a temperature that is close to, but not exactly the thermal critical temperature. Our finite-size study on this model yielded a correlation length exponent that agrees with that of the three-dimensional XY model with an error margin of six per cent.
Statistical Mechanics (cond-mat.stat-mech)
Instabilities, thermal fluctuations, defects and dislocations in the crystal-\(R_I\)-\(R_{II}\) rotator phase transitions of n-alkanes
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-18 20:00 EST
Soumya Kanti Ganguly, Prabir K. Mukherjee
The theoretical study of instabilities, thermal fluctuations, and topological defects in the crystal-rotator-I-rotator-II (\(X-R_{I}-R_{II}\)) phase transitions of n-alkanes has been conducted. First, we examine the nature of the \(R_{I}-R_{II}\) phase transition in nanoconfined alkanes. We propose that under confined conditions, the presence of quenched random orientational disorder makes the \(R_{I}\) phase unstable. This disorder-mediated transition falls within the Imry-Ma universality class. Next, we discuss the role of thermal fluctuations in certain rotator phases, as well as the influence of dislocations on the \(X-R_I\) phase transition. Our findings indicate that the Herringbone order in the \(X\)-phase and the Hexatic order in the \(R_{II}\)-phase exhibit quasi-long-range characteristics. Furthermore, we find that in two dimensions, the unbinding of dislocations does not result in a disordered liquid state.
Statistical Mechanics (cond-mat.stat-mech)
Antiferromagnetic diamond network as an efficient spin filter: Proposition of a spin-specific semi-conducting behavior
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Debjani Das Gupta, Santanu K. Maiti
We propose, for the first time, that an array of diamond plaquettes, each possessing vanishing net magnetization, can achieve complete spin polarization over a broad bias window. Furthermore, this system can be utilized to realize spin-specific semiconducting behavior. We describe the antiferromagnetic diamond network within a tight-binding framework, where spin-dependent scattering arises due to the interaction between itinerant electrons and local magnetic moments at different lattice sites. The mechanism underlying spin filtration relies on the specific arrangement of magnetic moments within individual plaquettes. We systematically investigate the spin polarization phenomenon under various input conditions, examining its dependence on network size, system temperature, and the magnetic flux threading each plaquette. Due to the network's geometry, we identify a sharply localized, highly degenerate energy level coexisting with conducting states. By tuning physical parameters, a small energy gap can be established between these degenerate localized states and the conducting energy band, enabling spin-specific \(p\)-type and \(n\)-type semiconducting behavior. Our findings offer a novel approach for designing future spintronic devices based on similar antiferromagnetic networks.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
10 pages, 13 figures (comments are welcome)
Ultrafast demagnetization dynamics of 4f antiferromagnets
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Maryna Pankratova, Vladislav Borisov, Danny Thonig, Rohit Pathak, Yoav William Windsor, Laurenz Rettig, Olle Eriksson, Arthur Ernst, Anders Bergman
We study the ultrafast demagnetization dynamics of LnRh\(_2\)Si\(_2\) (Ln \(=\) Pr, Nd, Sm, Gd, Tb, Dy, Ho) antiferromagnets (AFM) after excitation by a laser pulse, using a combination of density functional theory and atomistic spin and spin-lattice dynamics simulations. First, we calculate the Heisenberg interactions using the magnetic force theorem and compare two approaches, where the \(4f\) states of the rare earths are treated as frozen core states or as valence states with added correlation corrections. We find marked quantitative differences in terms of predicted Curie temperature for most of the systems, especially for those with large orbital moment of the rare earth cations. This can be attributed to the importance of indirect interactions of the \(4f\) states through the Si states, which depend on the binding energy of the \(4f\) states and coexists with RKKY-type interactions mediated by the conduction states. However, qualitatively, both approaches agree in terms of the predicted AFM ordering at low temperatures. In the second step, the atomistic dynamics simulations are combined with a heat-conserving two-temperature model, allowing for the calculation of spin and electronic temperatures during the magnetization dynamics simulations. Despite quite different demagnetization times, magnetization dynamics of all studied LnRh\(_2\)Si\(_2\) AFM exhibit similar two-step behavior, in particular, the first fast drop followed by slower demagnetization. We observe that the demagnetization amplitude depends linearly on laser fluence for low fluences, which is in agreement with experimental observations. We also investigate the impact of lattice dynamics on ultrafast demagnetization using coupled atomistic spin-lattice dynamics simulations and a heat-conserving three-temperature model, which confirm linear dependence of magnetisation on laser fluence.
Materials Science (cond-mat.mtrl-sci)
12 pages, 12 figures
Semiconducting behaviors at epitaxial Ca0.5TaO3 interfaces
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Guangdong Nie, Guanghui Han, Shengpu Huang, Huiyin Wu, Deshun Wang, Kangxi Liu, Hao Ding, Fangdong Tang, Licong Peng, Dashuai Ma, Young Sun, Changjiang Liu, Deshun Hong
Emergent phenomena take place in symmetry-breaking systems, notably the recently discovered two-dimensional electron gas and its tunable superconductivities near the KTaO3 interfaces. Here, we synthesized perovskite Ca0.5TaO3 films along both [001] and [111] orientations. Different from the KTaO3 system, Ca0.5TaO3 films show semiconducting behaviors when capped with LaAlO3 films in both [001] and [111] orientations. By growing films at higher temperatures, more oxygen vacancies can be introduced, and the carrier density can be tuned from ~ 1014 cm-2 to ~ 1016 cm-2. Another difference is that the superconducting transition temperature Tc in KTaO3 (111) increases linearly along with its carrier density, while the Ca0.5TaO3 (111) remains semiconducting when carrier density ranges from ~ 1014 cm-2 to ~ 1016 cm-2. Based on the density function theory calculation, Ca0.5TaO3 and KTaO3 show similar electronic band structures. According to the energy-dispersive X-ray spectroscopy, we found heavy Sr diffusion from the substrate to the Ca0.5TaO3 layer, which may destroy the interfacial conductivity. Our work demonstrates that besides the oxygen vacancies, electronic transport is sensitive to the atomic intermixing near the interface in tantulates.
Materials Science (cond-mat.mtrl-sci)
Three Magnetization Peaks in HgBa\(_2\)Ca\(_2\)Cu\(_3\)O\(_8\) Single Crystals
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-18 20:00 EST
Yongze Ye, Yuhao Liu, Wenshan Hong, Yuan Li, Hai-Hu Wen
By measuring magnetization hysteresis loops of the superconducting HgBa\(_2\)Ca\(_2\)Cu\(_3\)O\(_8\) single crystals (\(T_{\rm c}\) = 133 K), we observed three magnetization peaks in a wide temperature region. This is in contrast to the previous observation that there are only two magnetization peaks in many superconductors. Detailed analysis finds that the second peak here evolves from a kinky structure at low temperatures and gets enhanced at high temperatures; the third peak evolves from a general broad peak at low temperatures and evolves into a sharp peak and even a step-like one at high temperatures. We propose a general phase diagram to interpret these peaks, the second peak is corresponding to the order-disorder transition, while the third peak is associated with the elastic-plastic crossover. Our work unifies the understanding of different "second peak" structures in different systems and thus sheds new light in understanding the vortex dynamics in type-II superconductors.
Superconductivity (cond-mat.supr-con)
6 pages, 5 figures
Investigation of Softer Lattice Dynamics in Defect Engineered GeTe Crystals
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Saptak Majumder, Pintu Singha, Sharath Kumar C., Mayanak K. Gupta, Dharmendra Kumar, R. Mittal, D. K. Shukla, M.P Saravanan, Deepshikha Jaiswal-Nagar, Vinayak B. Kamble
In this paper, we investigated the low-temperature lattice dynamics in two GeTe crystals with varying Ge defect stoichiometry. The X-ray Diffraction (XRD) of the as-cleaved ingots indicate that the orientation is mainly along the h0l direction. From the Raman spectra, a comparison of the linewidth variation with temperature for the in-plane (E-mode) vibrations reveals a subtle enhancement around 170 K for the less stoichiometric crystal, depicting a more anharmonic nature, via the 4-phonon scattering processes. Furthermore, a comparison of the out-of-plane A_T^1 mode indicates a sensitivity of a weaker Raman signal ( about 239 cm -1) from disordered GeTe4 tetrahedra that has adversely affected the mode dynamics in the less stoichiometric sample (S1). However, this weaker signal is not observed for the more stoichiometric sample (S2) below 200 K. The Machine Learned Molecular Dynamics (MLMD) simulations performed to calculate the phonon spectral densities reveal that the heavier atom, Te dominate below 100 cm-1, while, the lighter Ge has more significant contribution above 100 cm-1. Thus, the change observed only in the 120 cm-1 (A_T^1) mode is justified by defects at the Ge sites. Specific heat capacity measurements are performed that show a broad hump near 14 K, when plotted as Cp/T^3 versus T indicative of a non-Debye nature. Hence, considering the two optical modes in the Raman spectra, a Debye and two-Einstein modes model is conceptualized to explain the low-temperature specific heat. These calculations reveal a softer bonding vis-a-vis lowering of Debye temperature in S1. Lower Einstein temperatures are also observed in S1, which is attributed to the easy activation of these localized modes that affect the harmonicity of the lattice. Finally, the low-temperature resistivity measurements reveal a reduction in the effective phonon frequency (w_e) through the estimation of Te.
Materials Science (cond-mat.mtrl-sci)
Understanding Magnesium Dissolution through Machine Learn-ing Molecular Dynamics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Zhoulin Liu, Jianchun Sha, Guang-Ling Song, Ziliang Wang, Yinghe Zhang
Magnesium alloys have become increasingly important for various potential industrial applications, especially in energy storage, due to their outstanding properties. However, a clear under-standing of the dissolution mechanism of magnesium in the most common aqueous environments re-mains a critical challenge, hindering the broader application of magnesium alloys. To address pending key controversies in magnesium alloys research, the atomic-scale hydrogen evolution process and dis-solution mechanism of magnesium were investigated by combining machine learning molecular dy-namics with density functional theory. These controversies include the presence of magnesium reaction intermediates, the formation of uni-positive Mg+, the specific reaction steps involved in hydrogen evo-lution and magnesium dissolution, and the generation and growth mechanisms of the surface films. The results indicate that the intermediate species in the magnesium dissolution process is solid-phase MgOH, which exhibits an MgO-like structure. The magnesium in MgOH is identified as the widely recognized uni-positive Mg+. The intermediate film is formed, consisting primarily of the MgOH phase with a small amount of MgO. This film grows inward by extending into the magnesium substrate. Un-der sufficient water availability, the film undergoes further oxidation to form Mg(OH)2. These findings highlight the critical role of the MgOH phase in the magnesium dissolution process, leading to the pro-posal of a dissolution model based on MgOH/MgO solid phases as intermediates. These insights deep-en the understanding of magnesium dissolution, pave the way for the development of more effective anti-corrosion strategies for magnesium alloys, and may also advance the utilization of magnesium in energy storage applications.
Materials Science (cond-mat.mtrl-sci), Atomic Physics (physics.atom-ph)
Anomalies in the electronic, magnetic and thermal behavior near the Invar compositions of Fe-Ni alloys
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Ananya Sahoo, Ayusa Aparupa Biswal, S.K. Parida, V. R. R. Medicherla, Soumya Shephalika Behera, M. N. Singh, A. Sagdeo, Sawani Datta, Abhishek Singh, Kalobaran Maiti
The structural and magnetic properties of Fe\(_{1-x}\)Ni\(_x\)~(\(x\) = 0.32, 0.36, 0.40, 0.50) alloys have been investigated using synchrotron based x-ray diffraction (XRD) technique with x-rays of wavelength 0.63658 Å down to 50 K temperature, magnetic measurement using superconducting quantum interference device (SQUID) magnetometer and high resolution x-ray photoelectron spectroscopy (XPS) with monochromatic AlK\(_\alpha\) radiation. The XRD studies suggest a single phase with fcc structure for \(x\) = 0.36, 0.40, and 0.50 ~alloys and a mixed phase for \(x\) = 0.32 alloy containing both bcc and fcc structures. The lattice parameter of the alloys exhibits a linear dependence on temperature giving rise to a temperature independent coefficient of thermal expansion (CTE). The lowest CTE is observed for \(x\) = 0.36 Invar alloy as expected while \(x\) = 0.50 alloy exhibits the highest CTE among the alloys studied. The CTE of the fcc component of mixed phase alloy is close to that of Invar alloy. The temperature dependence of magnetization of the alloys down to 2 K reveals an overall antiferromagnetic interactions within the ferromagnetic phase causing the magnetization decreasing with cooling. The field cooled and zero field cooled data show larger differences for the Invar compositions; this is also manifested in the magnetic hysteresis data at 2 K and 300 K.
Strongly Correlated Electrons (cond-mat.str-el)
7 pages, 6 figures, regular article
Wrapping nonspherical vesicles at bio-membranes
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-18 20:00 EST
Ajit Kumar Sahu, Rajkumar Malik, Jiarul Midya
The wrapping of particles and vesicles by lipid bilayer membranes is a fundamental process in cellular transport and targeted drug delivery. Here, we investigate the wrapping behavior of nonspherical vesicles, such as ellipsoidal, prolate, oblate, and stomatocytes, by systematically varying the bending rigidity of the vesicle membrane and the tension of the planar membrane. Using the Helfrich Hamiltonian, triangulated membrane models, and energy minimization techniques, we predict multiple stable wrapping states and identify the conditions for their coexistence. Our results demonstrate that softer vesicles bind more easily to planar membranes; however, achieving complete wrapping requires significantly higher adhesion strengths compared to rigid particles. As membrane tension increases, deep-wrapped states disappear at a triple point where shallow-wrapped, deep-wrapped, and complete-wrapped states coexist. The coordinates of the triple point are highly sensitive to the vesicle shape and stiffness. For stomatocytes, increasing stiffness shifts the triple point to higher adhesion strengths and membrane tensions, while for oblates it shifts to lower values, influenced by shape changes during wrapping. Oblate shapes are preferred in shallow-wrapped states and stomatocytes in deep-wrapped states. In contrast to hard particles, where optimal adhesion strength for complete wrapping occurs at tensionless membranes, complete wrapping of soft vesicles requires finite membrane tension for optimal adhesion strength. These findings provide new insights into the interplay between vesicle deformability, shape, and membrane properties, advancing our understanding of endocytosis and the design of advanced biomimetic delivery systems.
Soft Condensed Matter (cond-mat.soft)
13 main pages, 8 main figures, 11 pages SI, 12 SI figures
Filtering Spin and Orbital Moment in Centrosymmetric Systems
New Submission | Other Condensed Matter (cond-mat.other) | 2025-02-18 20:00 EST
Luciano Jacopo DOnofrio, Maria Teresa Mercaldo, Wojciech Brzezicki, Adam Klosinski, Federico Mazzola, Carmine Ortix, Mario Cuoco
The control of spin and orbital angular momentum without relying on magnetic materials is commonly accomplished by breaking of inversion symmetry, which enables charge-to-spin conversion and spin selectivity in electron transfer processes occurring in chiral media. In contrast to this perspective, we show that orbital moment filtering can be accomplished in centrosymmetric systems: the electron states can be selectively manipulated allowing for the preferential transfer of electrons with a particular orbital momentum orientation. We find that orbital moment filtering is indeed efficiently controlled through orbital couplings that break both mirror and rotational symmetries. We provide the symmetry conditions required for the electron transmission medium to achieve orbital filtering and relate them to the orientation of the orbital moment. The presence of atomic spin-orbit interaction in the centrosymmetric transmission medium leads to the selective filtering of spin and orbital moments. Our findings allow to identify optimal regimes for having highly efficient simultaneous spin and orbital moment filtering.
Other Condensed Matter (cond-mat.other), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
5 pages, 4 figures
Exceptionally High Nonlinear Optical Response in Two-dimensional Type II Dirac Semimetal Nickel di-Telluride (NiTe2)
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Saswata Goswami, Caique Campos de Oliveira, Bruno Ipaves, Preeti Lata Mahapatra, Varinder Pal, Suman Sarkar, Pedro A. S. Autreto, Samit K. Ray, Chandra Sekhar Tiwary
Nickel ditelluride (NiTe2) is a newly identified Type-II Dirac semimetal, showing novel characteristics in electronic transport and optical experiments. In this study, we explored the nonlinear optical properties of two-dimensional NiTe2 using experimental and computational techniques (density functional theory-based approach). Few layered two-dimensional NiTe2 (2D-NiTe2) are synthesized using liquid phase exfoliation (LPE), which is characterized using X-ray diffraction technique, transmission electron, and atomic force microscopy. The nonlinear refractive index and third-order nonlinear susceptibility of the prepared 2D-NiTe2 are determined from the self-induced diffraction pattern generated using different wavelengths ( 405, 532, and 650 nm) in the far field. In addition, the diffraction pattern generated by spatial self-phase modulation (SSPM) is further verified by varying concentration (2D-NiTe2 in the IPA solvent), wavelength (of incoming laser beams), and cuvette width (active path length). The high value of third-order nonlinear susceptibility (in order of 10-9 e.s.u.) determined using SSPM in the 2D-NiTe2 can be attributed to the laser-induced hole coherence effect. Lastly, utilizing the reverse saturable absorption property of 2D-hBN, asymmetric light propagation is also demonstrated in the 2D-NiTe2/2D-hBN heterostructure.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
56 pages, 19 figures
Absence of nontrivial local conserved quantities in the quantum compass model on the square lattice
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-18 20:00 EST
By extending the method developed by Shiraishi, we prove that the quantum compass model on the square lattice does not possess any local conserved quantities except for the Hamiltonian itself.
Statistical Mechanics (cond-mat.stat-mech), Mathematical Physics (math-ph), Quantum Physics (quant-ph)
15 pages, 2 figures
Circular Dichroism in Resonant Inelastic X-ray Scattering: Probing Altermagnetic Domains in MnTe
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
D. Takegami, T. Aoyama, T. Okauchi, T. Yamaguchi, S. Tippireddy, S. Agrestini, M. García-Fernández, T. Mizokawa, K. Ohgushi, Ke-Jin Zhou, J. Chaloupka, J. Kuneš, A. Hariki, H. Suzuki
X-ray magnetic circular dichroism provides a means to identify ferromagnetic, chiral, and altermagnetic orders via their time-reversal-symmetry (\(\mathcal{T}\)) breaking. However, differentiating magnetic domains related by crystallographic symmetries remains a technical challenge. Here we reveal a circular dichroism (CD) in the resonant inelastic x-ray scattering (RIXS) spectra from the altermagnetic MnTe. The azimuthal dependence of the RIXS-CD intensity of the magnon excitations indicates a dominant occupation of a single altermagnetic domain. The RIXS-CD in our scattering geometry is ascribed to the mirror-symmetry breaking associated with the \(\mathcal{T}\)-broken altermagnetic order. Our results establish RIXS-CD as a domain-sensitive probe of elementary excitations in quantum materials.
Strongly Correlated Electrons (cond-mat.str-el)
Enhancing catalyst activity of two-dimensional C\(_4\)N\(_2\) through doping for the hydrogen evolution reaction
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Bruno Ipaves, João F. Justo, James M. de Almeida, Lucy V. C. Assali, Pedro Alves da Silva Autreto
This study investigates the structural, electronic, and catalytic properties of pristine and doped C\(_4\)N\(_2\) nanosheets as potential electrocatalysts for the hydrogen evolution reaction. The pristine C\(_{36}\)N\(_{18}\) nanosheets exhibit limited HER activity, primarily due to high positive Gibbs free energies (\(>\) 2.2 eV). To enhance catalytic performance, doping with B, Si, or P at the nitrogen site was explored. Among these systems, B-doped C\(_{36}\)N\(_{17}\) nanosheets exhibit the most promising catalytic activity, with a Gibbs free energy close to zero (\(\approx\) -0.2 eV), indicating efficient hydrogen adsorption. Band structure, projected density of states, charge density, and Bader charge analyses reveal significant changes in the electronic environment due to doping. While stacking configurations (AA\('\)A\(''\) and ABC) have minimal effect on catalytic performance, doping - particularly with B -substantially alters the electronic structure, optimizing hydrogen adsorption and facilitating efficient HER. These findings suggest that B-doped C\(_{36}\)N\(_{17}\) nanosheets could serve as efficient cocatalysts when combined with metallic materials, offering a promising approach to enhance catalytic efficiency in electrocatalytic and photocatalytic applications.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
Spin-orbital mixing in the topological ladder of the two-dimensional metal PtTe\(_2\)
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
M. Qahosh, M. Masilamani, H. Boban, Xiao Hou, G. Bihlmayer, Y. Mokrousov, W. Karain, J. Minar, F. Reinert, J. Schusser, C. M. Schneider, L. Plucinski
We visualize the topological ladder and band inversions in PtTe\(_2\) using spin-polarized photoemission spectroscopy augmented by three-dimensional momentum imaging. This approach enables the detection of spin polarization in dispersive bands and provides access to topological properties beyond the reach of conventional methods. Extensive mapping of spin-momentum space reveals distinct topological surface states, including a surface Dirac cone at the binding energy \(E_B \sim 2.3\) eV and additional states at \(E_B \sim 1.6\) eV, \(E_B \sim 1.0\) eV, and near the Fermi level. The electronic structure analysis demonstrates strong hybridization between Pt and Te atomic orbitals, confirming the nontrivial topology of these surface states. Furthermore, by comparison to one-step model photoemission calculations, we identify a robust correlation between the initial-state and measured spin polarizations while revealing asymmetries in specific experimental spin textures. These asymmetries, absent in the initial states due to symmetry constraints, arise from the breaking of time-reversal symmetry during the photoemission process, emphasizing the crucial influence of symmetries on experimental signatures of topology.
Materials Science (cond-mat.mtrl-sci)
6 pages, 4 figures, and the supplement
On the fluctuations of the number of atoms in the condensate
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-02-18 20:00 EST
Maciej B. Kruk, Piotr Kulik, Malthe F. Andersen, Piotr Deuar, Mariusz Gajda, Krzysztof Pawłowski, Emilia Witkowska, Jan J. Arlt, Kazimierz Rzążewski
Bose-Einstein condensation represents a remarkable phase transition, characterized by the formation of a single quantum subsystem. As a result, the statistical properties of the condensate are highly unique. In the case of a Bose gas, while the mean number of condensed atoms is independent of the choice of statistical ensemble, the microcanonical, canonical, or grand canonical variances differ significantly among these ensembles. In this paper, we review the progress made over the past 30 years in studying the statistical fluctuations of Bose-Einstein condensates. Focusing primarily on the ideal Bose gas, we emphasize the inequivalence of the Gibbs statistical ensembles and examine various approaches to this problem. These approaches include explicit analytic results for primarily one-dimensional systems, methods based on recurrence relations, asymptotic results for large numbers of particles, techniques derived from laser theory, and methods involving the construction of statistical ensembles via stochastic processes, such as the Metropolis algorithm. We also discuss the less thoroughly resolved problem of the statistical behavior of weakly interacting Bose gases. In particular, we elaborate on our stochastic approach, known as the hybrid sampling method. The experimental aspect of this field has gained renewed interest, especially following groundbreaking recent measurements of condensate fluctuations. These advancements were enabled by unprecedented control over the total number of atoms in each experimental realization. Additionally, we discuss the fluctuations in photonic condensates as an illustrative example of grand canonical fluctuations. Finally, we briefly consider the future directions for research in the field of condensate statistics.
Quantum Gases (cond-mat.quant-gas)
33 pages + references, review
Interfacial spin-orbit coupling in superconducting hybrid systems
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-18 20:00 EST
A. A. Mazanik, Tim Kokkeler, I. V. Tokatly, F. Sebastian Bergeret
We investigate the effects of interfacial spin-orbit coupling (ISOC) on superconductors, focusing on its impact on electronic transport and spin-charge conversion. Using a symmetry-based nonlinear sigma model, we derive effective boundary conditions for the Usadel and Maxwell equations that account for spin-galvanic effect, spin relaxation, and spin precession. This approach allows for the analysis of various interfaces without relying on specific microscopic models. We apply these boundary conditions to derive ISOC-induced terms in the Ginzburg-Landau functional, which is then used to compute the critical temperature of superconducting films with ISOC subjected to an external magnetic field. Our findings show that, contrary to a recent prediction, the critical temperature of a film cannot be enhanced by an external magnetic field. Additionally, we demonstrate that the combination of ISOC and an external magnetic field leads to a superconducting diode effect. Its efficiency strongly depends on the interplay between the spin-galvanic and the spin relaxation terms. Our results provide a framework for understanding ISOC in superconducting systems and highlight the potential for optimizing diode efficiency through careful interface engineering
Superconductivity (cond-mat.supr-con)
20 pages, 3 figures
Signature of glassy dynamics in dynamic modes decompositions
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-02-18 20:00 EST
Zachary G. Nicolaou, Hangjun Cho, Yuanzhao Zhang, J. Nathan Kutz, Steven L. Brunton
Glasses are traditionally characterized by their rugged landscape of disordered low-energy states and their slow relaxation towards thermodynamic equilibrium. Far from equilibrium, dynamical forms of glassy behavior with anomalous algebraic relaxation have also been noted, e.g., in networks of coupled oscillators. Due to their disordered and high-dimensional nature, such systems have been difficult to study analytically, but data-driven methods are emerging as a promising alternative that may aid in their characterization. Here, we show that the gap between oscillatory and decaying modes in the Koopman spectrum vanishes in systems exhibiting algebraic relaxation. The dynamic mode decomposition, which is a data-driven spectral computation that approximates the Koopman spectrum, thus provides a model-agnostic signature for detecting and analyzing glassy dynamics. We demonstrate the utility of our approach through both a minimal example of one-dimensional ODEs and a high-dimensional example of coupled oscillators.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech), Pattern Formation and Solitons (nlin.PS)
4 page, 4 figures, plus supplement
Egg yolk as a model for gelation: from rheometry to flow physics
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-18 20:00 EST
Maxwell Marsh, Mohammad Tanver Hossain, Randy Ewoldt
Egg yolks are an excellent model for studying sol-gel transitions, particularly the power law viscoelasticity that defines the critical point of gelation. However, prior studies lack comprehensive datasets and fail to visualize flow behavior linked to temperature and time-dependent linear and nonlinear rheology. Here we present a detailed dataset characterizing egg yolk viscoelasticity across temperature, time, and forcing amplitude using oscillatory shear, step strain, step stress, and constant high strain rate. Novel protorheology visualizations link rheological properties with observable flow behavior. Our findings highlight the nuanced determination of the critical gel point, emphasizing observation timescale dependencies. We compare methods to identify critical temperatures for gelation, including power law viscoelasticity, moduli crossover, diverging zero-shear viscosity, and emerging equilibrium elastic modulus, while visualizing flow consequences near these transitions. Egg yolk is an accessible non-toxic material relevant to the physicist and the chef alike, making it ideal for understanding the rheology of critical gels. By integrating protorheology photos and videos with rigorous rheometric data, we deepen the understanding of critical gels, with broader impacts for teaching and modeling sol-gel transitions.
Soft Condensed Matter (cond-mat.soft)
Supplementary information (videos and dataset) will be published online at Physics of Fluids
Orbital Signatures of Density Wave Transition in La3Ni2O7-delta and La2PrNi2O7-delta RP-Nickelates Probed via in-situ X-ray Absorption Near-edge Spectroscopy
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-18 20:00 EST
Mingtao Li, Mingxin Zhang, Yiming Wang, Jiayi Guan, Nana Li, Cuiying Pei, N-Diaye Adama, Qingyu Kong, Yanpeng Qi, Wenge Yang
The report of superconductivity (SC) with Tc~80 K in bilayer Ruddlesden-Popper (RP) nickelate La3Ni2O7-delta have sparked considerable investigations on its normal state properties and SC mechanism under pressure and at low temperature. It is believed that the density wave (DW) at ~150 K plays an important role in SC emergence, but its nature remains largely underexplored. Here, we utilized temperature-dependent in-situ Ni K-edge X-ray Absorption Near-edge Spectroscopy (XANES) to probe the Ni-3d/4p electronic states of La3Ni2O7-delta and La2PrNi2O7-delta samples down to 4.8 K, enabling us to witness the evolution of both in-plane d_(x2-y2)/p_x (p_y) and out-of-plane d_(3z2-r2)/p_z orbitals of NiO6 octahedron across the DW transition. Main edge energy associated with Ni 4p orbital shows an anomalous decline near DW transition, signifying the occurrence of lattice distortions as a hallmark of charge density wave. Below DW transition, the enlarged crystal field splitting (CFS) indicates an enhanced NiO6 octahedral distortion. Intriguingly, magnetic Pr substituents could activate the mutual interplay of d_(x2-y2) and d_(3z2-r2) orbitals. We discussed its relevance to the favored bulk SC in the pressurized polycrystalline La2PrNi2O7-delta than pristine.
Superconductivity (cond-mat.supr-con)
24 pages, 7 figures
Density-dependent spin susceptibility and effective mass in monolayer MoSe2
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Chang Liu, Tongtong Jia, Zheng Sun, Yu Gu, Fan Xu, Kenji Watanabe, Takashi Taniguchi, Jinfeng Jia, Shiyong Wang, Xiaoxue Liu, Tingxin Li
Atomically thin MoSe2 is a promising platform for investigating quantum phenomena due to its large effective mass, high crystal quality, and strong spin-orbit coupling. In this work, we demonstrate a triple-gate device design with bismuth contacts, enabling reliable ohmic contact down to low electron densities, with a maximum Hall mobility of approximately 22,000 cm2/Vs. Low-temperature transport measurements illustrate metal-insulator transitions, and density-dependent quantum oscillation sequences. Enhanced spin susceptibility and density-dependent effective mass are observed, attributed to interaction effects and valley polarization. These findings establish monolayer MoSe2 as a versatile platform for further exploring interaction-driven quantum states.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Itinerant topological magnons and spin excitons in twisted transition metal dichalcogenides: Mapping electron topology to spin counterpart
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Wei-Tao Zhou, Zhao-Yang Dong, Zhao-Long Gu, Jian-Xin Li
Twisted transition metal dichalcogenides (tTMDs) provide a highly tunable platform to explore the interplay between strong correlation and topology. Among them, the properties involving the charge degree of freedom have been extensively studied, while those related to spin are much less investigated. Motivated by the recent discovery of integer and fractional quantum anomalous Hall effects in tMoTe\(_2\), where the flat-band ferromagnetism is one of the essential prerequisites, we investigate theoretically the spin excitations out of the flat-band ferromagnetic ground state in tMoTe\(_2\). Remarkably, we identify the itinerant magnons and spin excitons with nontrivial topology. We elaborate that the topology of these itinerant spin excitations, which are described as particle-hole bound states, inherits directly from that of the underlying electrons and is essentially different from that in local spin systems. Thus, we establish a direct relationship of the topology between the many-body excitations and their fundamental constituents. We further demonstrate that by tuning the displacement field, a topological transition for both the magnon and spin exciton happens, leading to a step-like change and bifurcation in the thermal Hall conductance, which could serve as unique and compelling evidence to be tested experimentally.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
10 pages, 4 figures in main text, 7 pages, 5 figures in supplementary
Dimension Effect of Nanocarbon Precursors on Diamond Synthesis and Transformation Mechanism under Extreme Conditions
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Jiaxin Ming, Jingyi Tian, Liming Zhao, Jiayin Li, Guoshuai Du, Lixing Kang, Zheng Hu, Yabin Chen
Diamond holds significant promise for a wide range of applications due to its exceptional physicochemical properties. Investigating the controlled diamond preparation from nanocarbon precursors with varying dimensions is crucial to optimize the transition conditions and even elucidate the daunting transformation mechanism, however, this remains outstanding challenge despite considerable effort. Herein, we report the imperative dimension effect of nanocarbon precursors on diamond synthesis and physical mechanism under high temperature and high pressure, by comparing the distinct transition processes of zero-dimensional (0D) carbon nanocages (CNCs) and one-dimensional (1D) carbon nanotubes (CNTs) from conventional graphite. The optical and structural characterizations evidently demonstrated that both 0D CNCs and 1D CNTs first undergo collapse and graphitization, followed by the formation of mixed amorphous carbon with embedded diamond clusters, eventually leading to cubic diamond. The plotted pressure-temperature diagram exhibits the unique dimension effect of carbon nanomaterials to diamond transformation. These results provide valuable insights into the phase transition mechanisms of diamond synthesis and its derivatives under extreme conditions.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
20 pages, 5 figures
Anisotropic Schottky-barrier-height in high-symmetry 2D WSe\(_2\): Momentum-space anisotropy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Nuo Xu, Xiao-Lin Zhao, Meng-Xue Ren, Ke-Xin Hou, Xiao-huan Lv, Rui-Ning Wang, Xing-Qiang Shi, Jiang-Long Wang
It is usually supposed that only low-symmetry two-dimensional (2D) materials exhibit anisotropy, here we show that high-symmetry 2D semiconductors can show significant anisotropy in momentum space due to the band structure anisotropy in k-space. The basic reason is that different k-points in the Brillouin zone have different symmetry. Using 2D semiconductor WSe\(_2\) as the example, we construct lateral heterostructures with zigzag and armchair connections to 2D metal NbSe\(_2\), and the electronic structure and contact characteristics of these two connections are analyzed. It is found that both connections exhibit p-type Schottky barrier height (SBH) but the sizes of SBH are very different (of 0.03 eV and 0.50 eV), mainly because the band-edge energies of WSe\(_2\) are different along the two mutually perpendicular directions in momentum space. There are two factors contributing to the SBH anisotropy: one is the different interface structure and the other is the band edge anisotropy of the 2D semiconductor WSe\(_2\). Since the two interface structures give only a difference in interface potential change by less than 0.1 eV, the SBH variation of ~0.47 eV is mainly from the band structure anisotropy in momentum-space. So, high-symmetry 2D materials may exhibit highly anisotropic electronic states in momentum space and this affects the transport properties. Our current work extends the research field of 2D material anisotropy to 2D materials with high real-space symmetry, thus greatly expands the candidate materials for anisotropic studies and provides new guidance for optimizing the performance of 2D material devices via controlling transport directions.
Materials Science (cond-mat.mtrl-sci)
Topological magnons and domain walls in twisted bilayer MoTe\(_2\)
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
We theoretically investigate the magnetic excitations in the quantum anomalous Hall insulator phase of twisted bilayer MoTe\(_2\) at a hole filling factor of \(\nu=1\), focusing on magnon and domain wall excitations. Using a generalized interacting Kane-Mele model, we obtain the quantum anomalous Hall insualtor ground state with spin polarization. The magnon spectrum is then computed via the Bethe-Salpeter equation, revealing two low-energy topological magnon bands with opposite Chern numbers. To further explore the magnon topology, we construct a tight-binding model for the magnon bands, which is analogous to the Haldane model. We also calculate the energy cost of domain walls that separate regions with opposite Chern numbers and bind chiral edge states. Finally, we propose an effective spin model that describes both magnon and domain wall excitations, incorporating Heisenberg spin interactions and Dzyaloshinskii-Moriya interactions. The coupling constants in this model are determined from the numerical results for magnons and domain walls. This model accounts for the Ising anisotropy of the system, captures the magnon topology, and allows for the estimation of the magnetic ordering temperature. Our findings provide a comprehensive analysis of magnetic excitations in twisted MoTe\(_2\) and offer new insights into collective excitations in moiré systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
13 pages,5 figures
Organometallic-Inorganic Hybrid MXenes with Tunable Superconductivity
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-18 20:00 EST
Qi Fan, Tao Bo, Wei Guo, Minghua Chen, Qing Tang, Yicong Yang, Mian Li, Ke Chen, Fangfang Ge, Jialu Li, Sicong Qiao, Changda Wang, Li Song, Lijing Yu, Jinghua Guo, Michael Naguib, Zhifang Chai, Qing Huang, Chaochao Dun, Ning Kang, Yury Gogotsi, Kun Liang
Ti-based two-dimensional transition-metal carbides (MXenes) have attracted attention due to their superior properties and are being explored across various applications1,2. Despite their versatile properties, superconductivity has never been demonstrated, not even predicted, for this important group of 2D materials. In this work, we have introduced an electrochemical intercalation protocol to construct versatile organometallic-inorganic hybrid MXenes and achieved tunable superconductivity in the metallocene-modified layered crystals. Through structural editing of MXene matrix at atomic scale and meticulously modulated intercalation route, Ti3C2Tx intercalated with metallocene species exhibits a superconductive transition temperature (Tc) of 10.2 K. Guest intercalation induced electron filling and strain engineering are responsible for the emerging superconductivity in this intrinsically non-superconducting material. Theoretically, simulated electron-phonon interaction effects further elucidate the nature of the changes in Tc. Furthermore, the Tc of crafted artificial superlattices beyond Ti-based MXenes have been predicted, offering a general strategy for engineering superconductivity and magnetism in layered hybrid materials.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
Nonlocal Electrical Detection of Reciprocal Orbital Edelstein Effect
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Weiguang Gao, Liyang Liao, Hironari Isshiki, Nico Budai, Junyeon Kim, Hyun-Woo Lee, Kyung-Jin Lee, Dongwook Go, Yuriy Mokrousov, Shinji Miwa, Yoshichika Otani
Spin-Orbitronics leverages the spin and orbital degrees of freedom in solids for information processing. The orbital Edelstein effect and orbital Hall effect, where the charge current induces a nonequilibrium orbital angular momentum, offer a promising method to manipulate nanomagnets efficiently using light elements. Despite extensive research, understanding the Onsager reciprocity of orbital transport, fundamentally rooted in the second law of thermodynamics and time-reversal symmetry, remains elusive. In this study, we experimentally demonstrate the Onsager reciprocity of orbital transport in an orbital Edelstein system by utilizing nonlocal measurements. This method enables the precise identification of the chemical potential generated by orbital accumulation, avoiding the limitations associated with local measurements. Remarkably, we observe that the direct and inverse orbital-charge conversion processes produce identical electric voltages, confirming Onsager reciprocity in orbital transport. Additionally, we find that the orbital decay length, approximately 100 nm at room temperature, is independent of Cu thickness and decreases with lowering temperature, revealing a distinct contrast to spin transport behavior. Our findings provide valuable insights into both the reciprocity of the charge-orbital interconversion and the nonlocal correlation of orbital degree of freedom, laying the ground for orbitronics devices with long-range interconnections.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Electrothermal manipulation of current-induced phase transitions in ferrimagnetic Mn\(_3\)Si\(_2\)Te\(_6\)
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Jiaqi Fang, Jiawei Hu, Xintian Chen, Yaotian Liu, Zheng Yin, Zhe Ying, Yunhao Wang, Ziqiang Wang, Zhilin Li, Shiyu Zhu, Yang Xu, Sokrates T. Pantelides, Hong-Jun Gao
Phase transitions driven by external stimuli are central to condensed matter physics, providing critical insights into symmetry breaking and emergent phenomena. Recently, ferrimagnetic (FiM) Mn3Si2Te6 has attracted considerable attention for its magnetic-field-induced insulator-metal transitions (IMTs) and unconventional current-driven phase transitions, yet the role of applied currents in the magnetic phase remains poorly understood. Here, by combining local magnetization probes and time-resolved transport measurements, we uncover an electrothermal origin for the current-induced first-order-like phase transitions, characterized by abrupt voltage jumps and distinct magnetic domain evolution. Current-voltage (I-V) characteristics measured under triangular waveforms exhibit strong non- reciprocal and hysteretic behaviors, which are significantly suppressed at frequencies ~1000 Hz. Time-resolved studies using rectangular pulsed currents demonstrate that the resistance dynamics closely mirror the equilibrium resistance-temperature profile, directly implicating Joule heating as the driving mechanism. Furthermore, we reveal that the intrinsic I-V response adheres to Ohm's law, displaying linearity across various magnetic fields and temperatures. Our work advocates for a cautious approach in distinguishing between genuine current-induced nonequilibrium quantum states and thermal effects.
Materials Science (cond-mat.mtrl-sci)
18 pages, four figures
Spin-chirality-driven second-harmonic generation in two-dimensional magnet CrSBr
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Dezhao Wu, Yong Xu, Meng Ye, Wenhui Duan
The interplay between magnetism and light can create abundant optical phenomena. Here, we demonstrate the emergence of an unconventional magnetization-induced second-harmonic generation (MSHG) stemming from vector spin chirality, denoted as chiral second-harmonic generation (SHG). Taking the antiferromagnetic (AFM) CrSBr bilayer as a prototype, we theoretically show that, via spin canting, the chiral SHG can be continuously tuned from zero to a value one order of magnitude larger than its intrinsic MSHG. Remarkably, chiral SHG is found to be proportional to spin chirality and spin-canting-induced electric polarization, while intrinsic MSHG is proportional to the Néel vector, demonstrating their different physical mechanisms. Additionally, we reveal a unique interference effect between these two types of MSHG under the reversal of spin-canting direction, generating a giant modulation of SHG signals. Our work not only uncovers a unique SHG with exceptional tunability but also promotes the applications of AFM optical devices and magnetoelectric detection techniques.
Materials Science (cond-mat.mtrl-sci)
Accepted by Science Advances
Imaging current flow and injection in scalable graphene devices through NV-magnetometry
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Kaj Dockx, Michele Buscema, Saravana Kumar, Tijmen van Ree, Abbas Mohtashami, Leon van Dooren, Gabriele Bulgarini, Richard van Rijn, Clara I. Osorio, Toeno van der Sar
The global electronic properties of solid-state devices are strongly affected by the microscopic spatial paths of charge carriers. Visualising these paths in novel devices produced by scalable processes would provide a quality assessment method that can propel the device performance metrics towards commercial use. Here, we use high-resolution nitrogen-vacancy (NV) magnetometry to visualise the charge flow in gold-contacted, single-layer graphene devices produced by scalable methods. Modulating the majority carrier type via field effect reveals a strong asymmetry between the spatial current distributions in the electron and hole regimes that we attribute to an inhomogeneous microscopic potential landscape, inaccessible to conventional measurement techniques. In addition, we observe large, unexpected, differences in charge flow through nominally identical gold-graphene contacts. Moreover, we find that the current transfer into the graphene occurs several microns before the metal contact edge. Our findings establish high-resolution NV-magnetometry as a key tool for characterizing scalable 2D material based devices, uncovering quality deficits of the material, substrate, and electrical contacts that are invisible to conventional methods.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph), Instrumentation and Detectors (physics.ins-det), Quantum Physics (quant-ph)
Storing quantum coherence in a quantum dot nuclear spin ensemble for over 100 milliseconds
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Harry E. Dyte, Santanu Manna, Saimon F. Covre da Silva, Armando Rastelli, Evgeny A. Chekhovich
States with long coherence are a crucial requirement for qubits and quantum memories. Nuclear spins in epitaxial quantum dots are a great candidate, offering excellent isolation from external environments and on-demand coupling to optical flying qubits. However, coherence times are limited to \(\lesssim1\) ms by the dipole-dipole interactions between the nuclei and their quadrupolar coupling to inhomogeneous crystal strain. Here, we combine strain engineering of the nuclear spin ensemble and tailored dynamical decoupling sequences to achieve nuclear spin coherence times exceeding 100 ms. Recently, a reversible transfer of quantum information into nuclear spin ensembles has been demonstrated in quantum dots. Our results provide a path to develop this concept into a functioning solid-state quantum memory suitable for quantum repeaters in optical quantum communication networks.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Point-group symmetry enriched topological orders
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
We study the classification of two-dimensional (2D) topological orders enriched by point-group symmetries, by generalizing the folding appraoch which was previously developed for mirror-symmetry-enriched topological orders. We fold the 2D plane hosting the topological order into the foundamental domain of the group group, which is a sector with an angle \(2\pi/n\) for the cyclic point group \(C_n\) and a sector with an angle \(\pi/n\) for the dihedral point group \(D_{2n}\), and the point-group symmetries becomes onsite unitary symmetries on the sector. The enrichment of the point-group symmetries is then fully encoded at the boundary of the sector and the apex of the section, which forms a junction between the two boundaries. The mirror-symmetry enrichment encoded on the boundaries is analyzed by the classification theory of symmetric gapped boundaries, and the point-group-symmetry enrichment encoded on the junction is analyzed by a framework for classifying symmetric gapped junctions between boundaries which we develop in this work. We show that at the junction, there are two potential obstructions, which we refer to as an \(H^1\) obstruction and an \(H^2\) obstruction, respectively. When the obstruction vanishes, the junction, and therefore the point-group-symmetry-enriched topological orders, are classified by an \(H^0\) cohomology class and an \(H^1\) cohomology class, which can be understood as an additional Abelian anyon and a symmetry charge attached to the rotation center, respectively. These results are consistent with the classification of onsite-symmetry-enriched topological orders, where the \(H^1\) and \(H^2\) obstructions and the junction corresponds to the \(H^3\) and \(H^4\) obstructions for onsite symmetries, respectively.
Strongly Correlated Electrons (cond-mat.str-el)
34 pages, 23 figures
Charge Orders in Fully Intercalated Bilayer TaSe\(_2\): Dependence on Interlayer Stacking and Intercalation Sites
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Yuhui Yan, Lingxiao Xiong, Feipeng Zheng
Recent advancements have established self-intercalation as a powerful technique for manipulating quantum material properties, with precisely controllable intercalation concentrations. Given the inherently rich phase diagrams of transition metal dichalcogenides (TMDCs), studying the self-intercalated TMDCs can offer promising candidates for investigating the interplay between various orderings. This work focuses on fully intercalated bilayer TaSe\(_2\) (Ta\(_3\)Se\(_4\)), which has recently been fabricated experimentally. By performing first-principles calculations, we demonstrate the suppression of an intrinsic \(3\times3\) charge density wave (CDW) in parent TaSe\(_2\) layers, and the emergence of \(2\times 2\), \(\sqrt{3} \times \sqrt{3}\), or the absence of a CDW in the intercalated layers, depending on the interlayer stacking orders and intercalation sites being occupied. Particularly, the \(2\times 2\) CDW shows an increase in electronic states at the Fermi level compared to its non-CDW phase. This unusual behavior contrasts with that of typical CDW materials in TMDCs. Furthermore, superconductivity is preserved in these Ta\(_3\)Se\(_4\) structures, with superconducting transition temperatures comparable to or substantially smaller than those of TaSe\(_2\). Spin-orbit coupling is found to enhance the density of states at Fermi levels while simultaneously reducing the electron-phonon coupling matrix elements. These two competing effects result in varying impacts on superconductivity across different Ta\(_3\)Se\(_4\) structures. Moreover, our calculations indicate that magnetic order is absent. Our study deepens the understanding of underlying physics in Ta\(_3\)Se\(_4\), and provides experimentally feasible candidates for studying CDW, superconductivity, and their interplay.
Materials Science (cond-mat.mtrl-sci), Superconductivity (cond-mat.supr-con)
10 pages, 7 figures
Interfacial Dzyaloshinskii-Moriya interaction in nonmagnetic/noncollinear-antiferromagnetic bilayers
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Yuta Yamane, Yasufumi Araki, Shunsuke Fukami
We study Dzyaloshinskii-Moriya interaction (DMI) appearing at the interface of a nonmagnetic/noncollinear-antiferromagnetic bilayer. DMI is an antisymmetric exchange interaction between neighboring magnetic spins, arising in the absence of inversion center between the spins and the explicit expression of which being dictated by system symmetry. We formulate the interfacial DMI for different crystalline orientations of the noncollinear antiferromagnet with stacked-Kagome lattice structure. From this formulation, we show that, when the Kagome planes are perpendicular to the sample film plane, the DMI serves as a uniaxial magnetic anisotropy for the antiferromagnetic order parameter. Our findings reveal a novel physical manifestation of a DMI, shedding a new light on microscopic mechanisms of the magnetic anisotropy in noncollinear antiferromagnets.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Strain engineering of valley-polarized hybrid excitons in a 2D semiconductor
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Abhijeet M. Kumar, Douglas J. Bock, Denis Yagodkin, Edith Wietek, Bianca Höfer, Max Sinner, Pablo Hernández López, Sebastian Heeg, Cornelius Gahl, Florian Libisch, Alexey Chernikov, Ermin Malic, Roberto Rosati, Kirill I. Bolotin
Encoding and manipulating digital information in quantum degrees of freedom is one of the major challenges of today's science and technology. The valley indices of excitons in transition metal dichalcogenides (TMDs) are well-suited to address this challenge. Here, we demonstrate a new class of strain-tunable, valley-polarized hybrid excitons in monolayer TMDs, comprising a pair of energy-resonant intra- and intervalley excitons. These states combine the advantages of bright intravalley excitons, where the valley index directly couples to light polarization, and dark intervalley excitons, characterized by low depolarization rates. We demonstrate that the hybridized state of dark KK' intervalley and defect-localized excitons exhibits a degree of circular polarization of emitted photons that is three times higher than that of the constituent species. Moreover, a bright KK intravalley and a dark KQ exciton form a coherently coupled hybrid state under energetic resonance, with their valley depolarization dynamics slowed down a hundredfold. Overall, these valley-polarized hybrid excitons with strain-tunable valley character emerge as prime candidates for valleytronic applications in future quantum and information technology.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
This manuscript consists of 10 pages and 4 figures
Disorder-induced liquid-solid phase coexistence in 2D electron systems
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Recent imaging experiments show a surprisingly robust regime of liquid-solid phase coexistence in a 2D electron system near the quantum melting/freezing transition, with the two phases mixed in mesoscopic domains. Strikingly, the experiments find no noticeable difference in electron density between the liquid and solid domains, which is at odds with both microemulsion scenarios and scenarios in which phase coexistence is driven by fluctuations of a long-ranged disorder potential. Here, we show that such phase coexistence without density difference can be induced by random fluctuations of a short-ranged disorder potential. We further show that disorder tends to stabilize the Wigner Crystal phase to higher densities, which is also consistent with the experiments.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
5+2 pages, 3 figures
High-pressure floating zone crystal growth of Sr\(_2\)IrO\(_4\)
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
S. J. Gomez Alvarado, Y. Pang, P. A. Barrera, D. Rout, C. Robison, Z. Porter, H. Z. Porter, E. A. Lawrence, E. N. Bassey, S. D. Wilson
Here we demonstrate the floating zone crystal growth of the \(J_\mathrm{eff}=1/2\) Mott insulator Sr\(_2\)IrO\(_4\). Historically, the growth of iridates from a ternary melt has been precluded by the extreme vapor pressure of the metal oxide species and the difficulty of maintaining the correct oxidation state of Ir at high temperatures. Here, we show that the application of a high-pressure oxygen growth environment stabilizes the Sr\(_2\)IrO\(_4\) phase, leading to the first demonstration of cm\(^{3}\)-scale crystals. In contrast to the conventional SrCl\(_2\) flux growth method, where poor control over disorder leads to strong sample dependence, the high-pressure floating zone growth enables active control over the homogeneity of the melt. Crystals grown via this technique possess qualitatively similar properties to those grown via flux, with a relatively sharp onset of antiferromagnetic order observed in temperature-dependent magnetization. Further, we demonstrate that by tuning the mixing rate of the melt, we are able to grow natively hole-doped Sr\(_2\)Ir\(_{1-y}\)O\(_4\), which exhibits a strongly modified magnetic and electronic response.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
8 pages, 4 figures
Correlative and in situ microscopy investigation of phase transformation, crystal growth and degradation of antimony sulfide thin films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Mingjian Wu, Maïssa K. S. Barr, Vanessa M. Koch, Martin Dierner, Tobias Dierke, Penghan Lu, Johannes Will, Rafal Dunin-Borkowski, Janina Maultsch, Julien Bachmann, Erdmann Spiecker
Antimony sulfide (Sb\(_2\)S\(_3\)), a compound of earth-abundant elements with highly anisotropic, quasi-layered crystal structure, triggered growing interest as a solar absorber in photovoltaics and as a phase change material in memory devices, yet challenges remain in achieving high-quality thin films with controlled nucleation and growth for optimal performance. Here, we investigate the phase transformation, crystal structure and properties, growth and degradation of atomic layer deposited Sb\(_2\)S\(_3\) thin films using in situ TEM and correlative ex situ analysis. The as-deposited amorphous films crystallized at 243°C, forming grains with an [100] out-of-plane texture and developed into tens to hundreds of micrometer, leaves-shaped grains. Introducing an ultra-thin ZnS interfacial layer increased nucleation density, and resulted in a few micrometer-sized, more uniform grains while retaining the overall [100] texture. In situ observations and subsequent crystal orientation analysis with cutting-edge 4D-STEM and EBSD revealed that the grains grew faster along the [010] ribbon direction and that the bare films underwent early-stage degradation, forming holes in amorphous regions during annealing. The ZnS interlayer mitigated degradation, stabilizing the films and improving their uniformity. These findings offer valuable insights for optimizing Sb\(_2\)S\(_3\) thin films for applications both as solar cell materials and phase change materials.
Materials Science (cond-mat.mtrl-sci)
13 pages, 5 figures
3D Electron Diffraction as GIWAXS Alternative for Quantitative Structural Characterization of Organic Solar Cells
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Irene Kraus, Mingjian Wu, Stefanie Rechberger, Johannes Will, Santanu Maiti, Andreas Kuhlmann, Marten Huck, Larry Lüer, Florian Bertram, Hans-Georg Steinrück, Tobias Unruh, Christoph J. Brabec, Erdmann Spiecker
We demonstrate elastically filtered 3D Electron Diffraction (3D ED) as a powerful alternative technique to Grazing Incidence Wide-Angle X-ray Scattering (GIWAXS) for quantitatively characterizing the structure of organic semiconductor films. Using a model material system of solvent vapor annealed DRCN5T:PC71BM thin film, which is employed in organic solar cells (OSCs), we extract the structural data obtained from 3D ED and compare with that from GIWAXS, utilizing both laboratory and synchrotron X-ray sources. Quantitative evaluation of the datasets in terms of peak positions, peak widths and mosaicity revealed good agreement between both techniques, qualifying 3D ED as an alternative tool for analyzing highly beam-sensitive organic thin films. Furthermore, the respective advantages and limitations of 3D ED and GIWAXS are discussed, emphasizing the unique capability of 3D ED to integrate seamlessly with the diverse imaging and spectroscopic modalities in modern TEM. This integration enriches the techniques of structural characterization of OSCs, paving the way for deeper insights into their structural properties and ultimately their performance.
Materials Science (cond-mat.mtrl-sci)
27 pages, 5 figures
Site-Decorated Model for Unconventional Frustrated Magnets with Ultranarrow Phase Crossover and Spin Reversal Transition
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-18 20:00 EST
The site-decorated Ising model is introduced to advance the understanding and physical realization of the recently discovered one-dimensional finite-temperature ultranarrow phase crossover in an external magnetic field, overcoming the complexity of the traditional bond-decorated models from geometric consideration. Furthermore, for higher-dimensional Ising models in the presence of an external magnetic field, while they remain unsolved, an exact solution about a novel spin-reversal transition -- accessible by a slight change in temperature or the magnetic field, even in the weak field limit -- is found to exist upon the site decoration. These results suggest a new route to energy-efficient applications in, e.g., data storage and processing, and call for materialization and device design with site decoration in, e.g., mixed \(d\)-\(f\) compounds, optical lattices, or neural networks.
Statistical Mechanics (cond-mat.stat-mech)
6 pages, 6 figures
Coherent Spin Pumping Originated from Sub-Terahertz Néel Vector Dynamics in Easy Plane α-Fe2O3/Pt
New Submission | Other Condensed Matter (cond-mat.other) | 2025-02-18 20:00 EST
Gregory Fritjofson, Atul Regmi, Jacob Hanson-Flores, Justin Michel, Junyu Tang, Fengyuan Yang, Ran Cheng, Enrique Del Barco
We present a thorough study of spin-to-charge current interconversion in bulk and thin films of (0001) {}-Fe2O3 /Pt heterostructures by means of all-optical polarization-controlled microwave excitation at sub-Terahertz frequencies. Our results demonstrate that coherent spin pumping is generated through excitations of both the acoustic and optical modes of antiferromagnetic resonance, provided that the corresponding selection rules are met for the relative orientation between the microwave magnetic field h_ac and the magnetic moment m_0 of the Hematite. In particular, our results unanimously show that while a microwave field with h_ac perpendicular to m_0 pumps a net spin angular momentum from the acoustic mode, spin pumping from the optical mode is only enabled when h_ac parallel to m_0, as expected from the selection rules imposed by the Neel vector dynamics. Our results support the current understanding of spin mixing conductance in antiferromagnetic/non-magnetic interfaces, contrary to recent reports where the absence of spin pumping from the optical mode in Hematite was interpreted as a cancellation effect between the diagonal and off-diagonal components of the spin mixing conductance. We also provide an explanation for the previously reported observations and show how the optical spin pumping actually vanishes for thin films, which we speculate being either due to an increased level of inhomogeneities or to insufficient film thickness for the optical mode to fully realize.
Other Condensed Matter (cond-mat.other)
14 pages, 4 figures
Predicted versatile topological nodal magnons in the icosahedral quasicrystal 1/1 approximants
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Rintaro Eto, Masahito Mochizuki, Shinji Watanabe
Using a recenly-estabilished band representation analysis, we discover two distinct types of topological nodal magnons in the real-space antiferroic ordering of whirling spin arrangements in the icosahedral quasicrystal 1/1 approximants, both of which originate from a composite band representation \(A\uparrow P_In\bar{3}(24)\) and its constituent \({}^1E_g\uparrow P_In\bar{3}(8)\) (or \({}^2E_g\uparrow P_In\bar{3}(8)\)). The first type is doubly-degenerate nodal line network and nodal planes associated with two-dimensional irreducible band representation, while the second type is a nodal line network due to accidental band inversions. Since our analysis, which relies solely on magnetocrystalline symmetry, is valid for a wide range of materials and spin textures belonging to the same magnetic space group irrespective of composition, these findings offer new universal insights into the research of quasicrystals and their approximants as well as a contribution to broadening the range of topological magnon-hosting materials.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
7 pages, 3 figures
Active Solids: Defect Self-Propulsion Without Flow
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-18 20:00 EST
Fridtjof Brauns, Myles O'Leary, Arthur Hernandez, Mark J. Bowick, M. Cristina Marchetti
The self-propulsion of +1/2 topological defects is a hallmark of active nematic fluids, where the defects are advected by the flow field they themselves generate. In this paper we propose a minimal model for defect self-propulsion in a nematic active solid: a linear elastic medium with an embedded nematic texture that generates active stress and associated elastic strains. We show that such coupling gives rise to self-propelled +1/2 defects that move relative to the elastic medium by local remodeling of the nematic texture without advection. This mechanism is fundamentally different from the fluid case and can lead to unbinding of defect pairs and stabilization of +1 defects. Our findings might help explain how orientational order, of, for example, muscle fibers, is reconfigured during morphogenesis in solid-like tissues. The proposed mechanism may, for instance, control motility and merging of +1/2 defects, which play a crucial role in setting up the body axis during Hydra regeneration.
Soft Condensed Matter (cond-mat.soft), Pattern Formation and Solitons (nlin.PS)
8 pages, 4 figures
Tracking Adiabaticity in Non-Equilibrium Many-Body Systems: The Hard Case of the X-ray Photoemission in Metals
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
G. Diniz, F. D. Picoli, L. N. Oliveira, I. D'Amico
The level of adiabaticity determines many properties of time-dependent quantum systems. However, a reliable and easy-to-apply criterion to check and track it remains an open question, especially for complex many-body systems. Here we test techniques based on metrics which have been recently proposed to quantitatively characterize and track adiabaticity. We investigate the time evolution of x-ray photoemission in metals, which displays a strongly out-of-equilibrium character, continuum energy spectrum, and experiences the Anderson orthogonality catastrophe: a nightmarish scenario for this type of test. Our results show that the metrics-based methods remains valid. In particular, we demonstrate that the natural local density distance is able not only to track adiabaticity, but also to provide information not captured by the corresponding Bures' or trace distances about the system's dynamics. In the process, we establish an explicit upper limit for this local density distance in terms of the trace distance, and derive a simple analytical solution that accurately describes the time evolution of a Fermi gas with a localized scattering potential for a large range of parameters. We also demonstrate that, for x-ray photoemission, the quantum adiabatic criterion, as commonly used, fails to predict and track adiabaticity. The local particle density is typically much simpler to compute than the corresponding quantum state and it is experimentally measurable: this makes the method tested extremely appealing.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Microscopic contact line dynamics dictate the emergent behaviors of particle rafts
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-18 20:00 EST
Ranit Mukherjee, Zih-Yin Chen, Xiang Cheng, Sungyon Lee
Fluid-fluid interfaces laden with discrete particles behave curiously like continuous elastic sheets, leading to their applications in emulsion and foam stabilization. Although existing continuum models can qualitatively capture the elastic buckling of these particle-laden interfaces -- often referred to as particle rafts -- under compression, they fail to link their macroscopic collective properties to the microscopic behaviors of individual particles. Thus, phenomena such as particle expulsion from the compressed rafts remain unexplained. Here, by combining systematic experiments with first-principle modeling, we reveal how the macroscopic mechanical properties of particle rafts emerge from particle-scale interactions. We construct a phase diagram that delineates the conditions under which a particle raft collapses via collective folding versus single-particle expulsion. Guided by this theoretical framework, we demonstrate control over the raft's failure mode by tuning the physicochemical properties of individual particles. Our study highlights the previously overlooked dual nature of particle rafts and exemplifies how collective dynamics can arise from discrete components with simple interactions.
Soft Condensed Matter (cond-mat.soft)
13 pages, 9 figures (in review in Physical Review Letters)
Time-dependent approach to the X-ray photoemission problem
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
F. D. Picoli, G. Diniz, M. P. Lenzarini, I. D'Amico, L. N. Oliveira
X-ray photoemission from simple metals has been thoroughly studied, experimentally, and theoretically, in the frequency domain. Here we investigate the same problem in the time domain, with the ultimate purpose of improving the numerical renormalization-group method. We focus our study on the time dependence of the photoemission current \(\mathcal{F}(t)\), a fidelity, in the terminology of quantum information. To establish benchmarks, we first calculate \(\mathcal{F}(t)\) analytically and numerically for a tight-binding model. Analytically, we derive an approximate expression that becomes very precise at large times. Numerically, we diagonalize the tight-binding Hamiltonian and compute \(\mathcal{F}(t)\) from its eigenvalues and eigenvectors, a straightforward procedure that covers the segment of the \(t\) axis in which the analytical expression is less accurate. The time dependence shows features of physical interest that have received little attention because they are inconspicuous in the frequency domain; the analytical expression provides a simple interpretation and traces them to an unusual form of interference. We then turn to eNRG, a recently proposed real-space variant that is more flexible than Wilson's NRG method, and present two complementary time-dependent algorithms. Comparison with the benchmarks shows that one of the eNRG algorithms yields virtually exact photocurrents with a small fraction of the computational effort to diagonalize the tight-binding Hamiltonian. The second algorithm is computationally less demanding and produces precise results at long times. In contemplation of extensions to correlated-impurity models, we identify sources of deviation and discuss the virtues and drawbacks of the two procedures.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
Diffuse-charge dynamics across a capacitive interface in a DC electric field
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-18 20:00 EST
Shuozhen Zhao, Bhavya Balu, Zongxin Yu, Michael J. Miksis, Petia M. Vlahovska
Cells and cellular organelles are encapsulated by nanometrically thin membranes whose main component is a lipid bilayer. In the presence of electric fields, the ion-impermeable lipid bilayer acts as a capacitor and supports a potential difference across the membrane. We analyze the charging dynamics of a planar membrane separating bulk solutions with different electrolyte concentrations upon the application of an applied uniform DC electric field. The membrane is modeled as a zero-thickness capacitive interface. The evolution of the electric potential and ions distributions in the bulk are solved for using the Poisson-Nernst-Planck (PNP) equations. Asymptotic solutions are derived in the limit of thin Debye layers and weak fields (compared to the thermal electric potential).
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
Valency, charge-transfer, and orbital-dependent correlation in bilayer nickelates Nd3Ni2O7
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Daisuke Takegami, Takaki Okauchi, Edgar Abarca Morales, Kouto Fujinuma, Mizuki Furo, Masato Yoshimura, Ku-Ding Tsuei, Grace A. Pan, Dan Ferenc Segedin, Qi Song, Hanjong Paik, Charles M. Brooks, Julia A. Mundy, Takashi Mizokawa, Liu Hao Tjeng, Berit H. Goodge, Atsushi Hariki
We examine the bulk electronic structure of Nd3Ni2O7 using Ni 2p core-level hard x-ray photoemission spectroscopy combined with density functional theory + dynamical mean-field theory. Our results reveal a large deviation of the Ni 3d occupation from the formal Ni2.5+ valency, highlighting the importance of the charge-transfer from oxygen ligands. We find that the dominant d8 configuration is accompanied by nearly equal contributions from d7 and d9 states, exhibiting an unusual valence state among Ni-based oxides. Finally, we discuss the Ni dx2-y2 and dz2 orbital-dependent hybridization, correlation and local spin dynamics.
Strongly Correlated Electrons (cond-mat.str-el)
Why is the strength of a polymer network so low?
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-18 20:00 EST
Shaswat Mohanty, Jose Blanchet, Zhigang Suo, Wei Cai
Experiments have long shown that a polymer network of covalent bonds commonly ruptures at a stress that is orders of magnitude lower than the strength of the covalent bonds. Here we investigate this large reduction in strength by coarse-grained molecular dynamics simulations. We show that the network ruptures by sequentially breaking a small fraction of bonds, and that each broken bond lies on the minimum "shortest path". The shortest path is the path of the fewest bonds that connect two monomers at the opposite ends of the network. As the network is stretched, the minimum shortest path straightens and bears high tension set by covalent bonds, while most strands off the path deform by entropic elasticity. After a bond on the minimum shortest path breaks, the process repeats for the next minimum shortest path. As the network is stretched and bonds are broken, the scatter in lengths of the shortest paths first narrows, causing stress to rise, and then broadens, causing stress to decline. This sequential breaking of a small fraction of bonds causes the network to rupture at a stress that is orders of magnitude below the strength of the covalent bonds.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech), Computational Physics (physics.comp-ph)
11 pages, 5 figures
Interaction-driven losses for atoms in a dark-state lattice
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-02-18 20:00 EST
In this work we estimate the collisional loss rate of ultracold bosons in the optical potential featuring subwavelength-width peaks. This is established by using \(\Lambda\) arrangement of three atomic states coupled (almost) resonantly by lasers. Using Fermi's Golden Rule, we find that the loss rate is influenced by the overall strength of the lasers, with the largest losses occurring when the two-photon transition is blue-detuned from the excited state of the \(\Lambda\) system. Overall, the predicted loss rates are low, which may allow the use of ultracold bosons in the construction of dark-state potentials in the \(\Lambda\)-type many-level system.
Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
10 pages, 6 figures
Revisiting the charge-density-wave superlattice of 1\(T\)-TiSe\(_2\)
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Wei Wang, Patrick Liu, Lijun Wu, Jing Tao, Genda Gu, Alfred Zong, Yimei Zhu
A number of intriguing phenomena, including exciton condensation, orbital ordering, and emergence of chirality, have been proposed to accompany charge-density-wave (CDW) formation in the layered transition metal dichalcogenide 1\(T\)-TiSe\(_2\). Explaining these effects relies on knowledge of the atomic displacement pattern underlying the CDW, yet structural proposals based on spatially-averaging bulk crystal diffraction and surface-dependent scanning tunneling microscopy have remained inconsistent. Here, we revisit the CDW superlattice structure with selected-area electron diffraction, a bulk-sensitive probe capable of capturing sub-micrometer spatial variations while maintaining high momentum resolution. We resolved two distinct, spatially separated CDW phases characterized by different interlayer ordering. In both phases, previously reported atomic displacement patterns fail to account for the observed extinction rules. Instead, our analysis reveals a new superlattice structure, which features a large number of nearly degenerate CDW domains. These findings not only provide a new basis for understanding the gyrotropic electronic order and metastability in 1\(T\)-TiSe\(_2\), they also underscore the importance of bulk-sensitive mesoscopic techniques in investigating materials that host unconventional superlattices.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Physics-Informed Gaussian Process Classification for Constraint-Aware Alloy Design
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Christofer Hardcastle, Ryan O Mullan, Raymundo Arroyave, Brent Vela
Alloy design can be framed as a constraint-satisfaction problem. Building on previous methodologies, we propose equipping Gaussian Process Classifiers (GPCs) with physics-informed prior mean functions to model the boundaries of feasible design spaces. Through three case studies, we highlight the utility of informative priors for handling constraints on continuous and categorical properties. (1) Phase Stability: By incorporating CALPHAD predictions as priors for solid-solution phase stability, we enhance model validation using a publicly available XRD dataset. (2) Phase Stability Prediction Refinement: We demonstrate an in silico active learning approach to efficiently correct phase diagrams. (3) Continuous Property Thresholds: By embedding priors into continuous property models, we accelerate the discovery of alloys meeting specific property thresholds via active learning. In each case, integrating physics-based insights into the classification framework substantially improved model performance, demonstrating an efficient strategy for constraint-aware alloy design.
Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG)
When Homogeneous Systems Meet Dissipation and Disorder
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-02-18 20:00 EST
Xixi Feng, Ao Zhou, Feng Lu, Gao Xianlong, Shujie Cheng
We investigate the localization and topological properties of the non-equilibrium steady state (NESS) in a one-dimensional homogeneous system. Our results demonstrate that, despite the absence of disorder in the initial system, the NESS can exhibit localization under bond dissipation. Conversely, for an initially flat-band system with compactly localized wave functions, the NESS is delocalized. These dissipation-driven localization and delocalization phenomena are clearly distinguished using Wigner distributions. Furthermore, we find that the initial localization characteristics of the system significantly influence the localization properties of the NESS. Drawing upon the concept of Bose-Einstein condensate broadening in cold-atom experiments, along with experimental data, we systematically characterize the impact of disorder on the localization and topological properties of the NESS. The phase diagram reveals that the NESS can be topologically non-trivial even when the initial state is topologically trivial, and that the topological triviality of the initial state weakens the topological non-triviality of the NESS. This work provides new insights into the localization and topological phase transitions in homogeneous systems induced by bond dissipation and disorder.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
6 pages, 6 figures
Photoinduced twist and untwist of moiré superlattices in TMDC heterobilayers
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
C. J. R. Duncan, A. C. Johnson, I. Maity, A. Rubio, M. Gordon, A. C. Bartnik, M. Kaemingk, W. H. Li, M. B. Andorf, C. A. Pennington, I. V. Bazarov, M. W. Tate, D. A. Muller, J. Thom-Levy, S. M. Gruner, A . M. Lindenberg, F. Liu, J. M. Maxson
Two-dimensional twisted bilayer moiré structures provide a versatile material platform for realizing a rich variety of strongly correlated electronic quantum phases intricately coupled with the periodically modulated lattice structures. In this work, we use ultrafast electron diffraction to directly reveal the photoinduced dynamic evolution of the moiré superlattice in \(2^\circ\) and \(57^\circ\) twisted WSe\(_2\)/MoSe\(_2\) heterobilayers. Upon above-band-gap photoexcitation, the moiré superlattice diffraction features are enhanced within 1 ps and subsequently suppressed several picoseconds after, accompanied by a collective lattice excitation of a moiré phonon mode with sub-THz frequency. This unique response deviates markedly from typical photoinduced lattice heating, and suggests dynamic twisting and untwisting of the local moiré chiral structure. We infer large oscillations in the local twist angle, approaching \(1^\circ\) peak to trough, that are driven by ultrafast charge carrier excitation and relaxation -- a phenomenon further supported by molecular dynamics simulations. Our findings suggest a novel approach for real-time dynamic reconfiguration of moire superlattices to achieve ultrafast modulation of their strongly correlated behaviors.
Materials Science (cond-mat.mtrl-sci)
High Quality Single Crystal of Kitaev Spin Liquid Candidate Material RuBr3 Synthesized under High Pressure
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Bowen Zhang, Xiangjun Li, Limin Yan, Wenbo Li, Nana Li, Jianfa Zhao, Xiaobing Liu, Shun-Li Yu, Zhiwei Hu, Wenge Yang, Runze Yu
Kitaev quantum spin liquids have attracted significant attention in condensed matter physics over the past decade. To understand their emergent quantum phenomena, high-quality single crystals of substantial size are essential. Here, we report the synthesis of single crystals of the Kitaev quantum spin liquid candidate RuBr3, achieving millimeter-sized crystals through a self-flux method under high pressure and high temperature conditions. The crystals exhibit well-defined cleavage planes with a lustrous appearance. Transport characterizations exhibit a narrow band-gap semiconducting behavior with 0.13 eV and 0.11 eV band-gap in ab plane and along c axis, respectively. Magnetic measurement shows a transition to antiferromagnetic (AFM) state at approximately 29 K both in ab plane and along c axis. Notably, the Néel temperature increases to 34 K with an applied magnetic field of up to 7 T in the ab plane, but without any change along c axis. The large size and high quality of RuBr3 single crystals provide a valuable platform for investigating various interactions, particularly the Kitaev interaction, and for elucidating the intrinsic physical properties of Kitaev quantum spin liquids.
Strongly Correlated Electrons (cond-mat.str-el)
Chinese Physics Letters accepted
Application of Many-body Non-perturbative Theories to the Three-Dimensional Attractive Hubbard Model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Junnian Xiong, Hui Li, Yingze Su, Dingping Li
The attractive Fermi-Hubbard model stands out as a simple model for studying the pairing and superconductivity of fermions on a lattice. In this article, we apply several many-body theories in the three-dimensional attractive Hubbard model. Specifically, we compare the results of various GW methods with DQMC simulations and observe that they provide reliable results in the weak to intermediate coupling regime. The critical exponents also agree well with the accurate results obtained from the 3D XY model. In the superconducting phase, the post-GW method significantly improves the description of Green's functions and density of states. Additionally, we propose a method to determine the temperature at which the pseudogap appears.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
24 pages, 8 figures
Non-equilibrium distribution function in ultra-fast processes
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-18 20:00 EST
A simple expression for the non-equilibrium distribution function in
ultra-fast transient processes is proposed. Postulating its dependence
on temporal derivatives of the equilibrium integrals of motion,
non-equilibrium analogues of the thermodynamic relationships are derived
and the conditions that maximize the non-equilibrium entropy are
identified. A rigorous threshold between slow" andfast"
processes is suggested, identifying the range of applicability of
classical quasi-equilibrium description. The proposed theory is
validated by deriving the known law of inertial heat conduction, which
accounts for finite speed of thermal propagation. Finally, a new
expression for the non-equilibrium work is derived, revealing two kinds
of pressure that emerge in fast non-equilibrium.
Statistical Mechanics (cond-mat.stat-mech), Mathematical Physics (math-ph), Chemical Physics (physics.chem-ph)
10 pages 1 figure
Computational Study of Magnetic Behaviour in Ni-Adsorbed Nb2C-OF MXene using Density Functional Theory
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Zarah Khan, Saleem Ayaz Khan, Ayesha Zaheer, Syed Rizwan
Magnetic 2D materials have achieved significantly consideration owing to their encouraging applications. A variation of these 2D materials by occurrence of defects, by the transition-metal doping or adsorption or by the surface functionalization can initiate both the spin-polarization and magnetic properties in these materials. Density functional theory (DFT) is used to determine the electric, magnetic properties along with the electronic structures and stability of synthesized two-dimensional materials. This work describes the magnetic properties of Ni-ad-Nb2C-OF MXene. The study focuses on the computational approach based first principal calculation providing insight onto the magnetic properties of adsorbed compound and comparing it with pristine Nb2C-OF MXene. The pristine Nb2C-OF and Ni-ad-Nb2C-OF structures are simulated and optimized using Wien2k software. Using exchange-correlational functionals; spin-GGA and spin-GGA+U (for Nickel U= 6eV), Ni-ad-Nb2C-OF electronic band structure is found to be metallic having magnetic moment calculated +1.01516{}_ showing its non-superconducting and ferromagnetic behaviour. Owing to this magnetic nature, this 2D compound can be used for new upcoming applications such as spintronics and nano magnetic data storage devices.
Materials Science (cond-mat.mtrl-sci)
9 figures
Journal of Magnetism and Magnteic Materials, 2025
Competition Between Multiferroic and Magnetic Soliton Lattice States in DyFeO\(_3\)
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
S. E. Nikitin, N. D. Andriushin, Ø. S. Fjellvåg, E. Pomjakushina, A. A. Turrini, S. Artyukhin, C. W. Schneider, M. Mostovoy
Simultaneous breaking of time reversal and inversion symmetries in multiferroics couples ferroelectricity to magnetism and is a source of unusual physical phenomena that can be used in next-generation electronic devices. A notable example is DyFeO\(_3\), which under applied magnetic fields exhibits a giant linear magnetoelectric response and a large spontaneous electric polarization induced by coexisting orders of Fe and Dy spins. Here, we use high-resolution neutron diffraction to show that at zero field DyFeO\(_3\) hosts an incommensurate magnetic soliton lattice formed by spatially ordered Dy domain walls with an average domain size of 231(8) Å. The long-ranged interaction between the domain walls is mediated by magnons propagating through the Fe subsystem and is analogous to the Yukawa force in particle physics. An applied magnetic field destroys the long-ranged incommensurate order, unlocks the linear magnetoelectric response and stabilizes the ferroelectric state. The magnetic domain walls are electrically charged and the soliton array dimerizes when both electric and magnetic fields are applied. Numerical simulations with experimental parameters suggest, that the generic competition between the ferroelectric and incommensurate states can be effectively controlled by an applied electric field.
Strongly Correlated Electrons (cond-mat.str-el)
Large Deviation Theory for Bose Gas of Photons and Planck's Oscillators
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-18 20:00 EST
We utilize large deviation theorems to analyze the distributions of a Bose gas of photons and Planck's identical linear oscillators. By applying the Boltzmann-Sanov and Cramér-Chernoff theorems, we calculate the large deviation probabilities, entropies, and rate functions for the spatial and energy distributions of both photons and Planck's oscillators. Our study reproduces the results of Bose and Planck within the framework of large deviation theory.
Statistical Mechanics (cond-mat.stat-mech)
6 Pages
Weak coupling approach to magnetic and orbital susceptibilities for superconducting states in multiorbital electron-phonon coupled model
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-18 20:00 EST
Natsuki Okada, Tatsuya Miki, Shintaro Hoshino
Alkali-doped fullerides are molecular-based superconductors with multiple active orbitals. In this paper, using the Eliashberg theory with the retardation effect of Jahn-Teller phonons, we study the response of the spin-singlet superconducting state relevant to fulleride materials. The spin Zeeman field is not active for the singlet pairing state, and the magnetic orbital field, which physically generates a circular electron motion inside the fullerene molecule, is also shown to be inactive. On the other hand, the electric orbital (or quadrupolar) field, which corresponds to a uniaxial distortion, remains active across the superconducting phase transition. This is understood by the orbital-symmetric structure of the Cooper pair, which is susceptible to the electric orbital field, while it is not the case for the magnetic orbital field which tends to create an antisymmetric part.
Superconductivity (cond-mat.supr-con)
8 pages, 2 figures
Effects of antiferromagnetic coupling and pinning on domain wall dynamics in synthetic ferrimagnets
New Submission | Other Condensed Matter (cond-mat.other) | 2025-02-18 20:00 EST
Sougata Mallick, Nicolas Reyren, André Thiaville, Philippe Ohresser, Nicolas Jaouen, Vincent Cros, Vincent Jeudy
Domain wall (DW) dynamics in antiferromagnetic (AFM) systems offer the advantages over their ferromagnetic counterparts of having faster and more energy efficient manipulation due to the absence of net magnetization, leading to reduced magnetic crosstalk and improved performance in spintronic devices. A comprehensive analysis of DW dynamics across regimes such as creep, depinning, and flow is well established in ferromagnetic systems but remains lacking in AFM-coupled systems. In this study, we explore the nature of DW dynamics in synthetic ferrimagnetic multilayers composed of Pt|Co|Tb|Al for different Tb thickness, focusing on the underlying pinning parameters, and on the different regimes of DW dynamics driven by spin-orbit torques (SOTs). We find that due to the AFM coupling between Co and Tb, the magnetic moment of Tb increases with Tb thickness resulting in a reduced saturation magnetization and an enhanced depinning field. The DW disorder interaction is found to vary weakly with the AFM coupling between Co and Tb, while the complete withdrawal of the Tb layer strongly increases the anisotropy and the DW pinning. Furthermore, we propose a novel approach to measure effective SOTs by comparing depinning transitions in current and field-induced DW motion. This research reveals new insights into DW dynamics in coupled AFM systems, highlighting enhancements in mobility through optimized SOTs and pinning landscapes.
Other Condensed Matter (cond-mat.other)
12 pages, 9 figures
High-Temperature Superconductivity from Finite-Range Attractive Interaction
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Dmitry Miserev, Joel Hutchinson, Herbert Schoeller, Jelena Klinovaja, Daniel Loss
In this letter we consider \(D\)-dimensional interacting Fermi liquids, and demonstrate that an attractive interaction with a finite range \(R_s\) that is much greater than the Fermi wavelength \(\lambda_F\) breaks the conventional BCS theory of superconductivity. In contrast to the BCS prediction of a finite superconducting gap for all attractive contact interactions, we show that a finite-range interaction does not induce a superconducting gap. Instead, the pair susceptibility develops a power-law singularity at zero momentum and zero frequency signaling quantum critical behavior without long-range ordering. Starting from this, we show that superconductivity can be stabilized by adding a short-range attractive interaction, which is always present in real electronic systems. As an example, we consider a layered quasi-two-dimensional material with attractive electron-electron interactions mediated by optical phonons. We demonstrate a dome shape of the critical temperature \(T_c\) versus doping, strongly suppressed isotope effect, and a weak dependence of the optimal doping and maximal \(T_c^\ast \sim 0.1 E_F\) on the interaction range at \(R_s \gg \lambda_F\), \(E_F\) is the Fermi energy. We believe that these results could be relevant to high-temperature superconductors.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
Simulation-based Super-Resolution EBSD for Measurements of Relative Deformation Gradient Tensors
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Aimo Winkelmann, Grzegorz Cios, Konrad Perzyński, Tomasz Tokarski, Klaus Mehnert, Łukasz Madej, Piotr Bała
We summarize a data analysis approach for electron backscatter diffraction (EBSD) which uses high-resolution Kikuchi pattern simulations to measure isochoric relative deformation gradient tensors from experimentally measured Kikuchi patterns of relatively low resolution. Simulation-based supersampling of the theoretical test diffraction patterns enables a significant precision improvement of tensor parameters obtained in best-fit determinations of strains and orientations from low-resolution experimental patterns. As an application, we demonstrate high-resolution orientation and strain analysis for the model case of hardness test indents on a Si(100) wafer, using Kikuchi patterns of variable resolution. The approach shows noise levels near \(1 \times 10^{-4}\) in the relative deviatoric strain norm and in the relative rotation angles on nominally strain-free regions of the silicon wafer. The strain and rotation measurements are interpreted by finite element simulations. While confirming the basic findings of previously published studies, the present approach enables a potential reduction in the necessary pattern data size by about two orders of magnitude. We estimate that pattern resolutions in the order of \(256\times256\) pixels should be enough to solve a majority of EBSD analysis tasks using pattern matching techniques.
Materials Science (cond-mat.mtrl-sci)
Bose-Bose gases with nonuniversal corrections to the interactions: a droplet phase
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-02-18 20:00 EST
Through an effective quantum field theory within Bogoliubov's framework and taking into account nonuniversal effects of the interatomic potential we analytically derive the leading Gaussian zero- and finite-temperature corrections to the equation of state of ultracold interacting Bose-Bose gases. We calculate the ground-state energy per particle at zero and low temperature for three- two- and one-dimensional two-component bosonic gases. By tuning the nonuniversal contribution to the interactions we address and establish conditions under which the formation and stability of a self-bound liquidlike phase or droplet with nonuniversal corrections to the interactions DNUC) is favorable. At zero temperature in three-dimensions and considering the nonuniversal corrections to the attractive interactions as a fitting parameter the energy per particle for DNUC is in good agreement with some diffusion Monte Carlo results. In two dimensions the DNUC present small deviations regarding conventional droplets. For the one-dimensional DNUC the handling of the nonuniversal effects to the interactions achieves a qualitative agreement with the trend of some available Monte Carlo data in usual droplets. We also introduce some improved Gross-Pitaevskii equations to describe self-trapped DNUC in three, two and one dimension. We briefly discuss some aspects at low temperature regarding nonuniversal corrections to the interactions in Bose-Bose gases. We derive the dependencies on the nonuniversal contribution to the interactions but also on the difference between intra- and inter-species coupling constants. This last dependence crucially affect the three- and the two-dimensional DNUC driving thus to a thermal-induced instability. This thermal instability is also present in one-dimensional Bose-Bose gases, but it is not relevant on the formation of DNUC...
Quantum Gases (cond-mat.quant-gas)
32 pages
Ann. Phys. 475 (2025) 169955
Enhanced Gilbert Damping via Cubic Spin-Orbit Coupling at 2DHG/Ferromagnetic Insulator Interface
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
We investigate the enhancement of Gilbert damping at 2DHG/ferromagnetic insulator (FI) interfaces, where spin pumping from the FI layer injects spins into the 2DHG, and cubic Rashba spin-orbit coupling (RSOC) significantly boosts spin relaxation and spin-pumping efficiency compared to 2DEG systems. The dominant contribution to spin damping arises from interband transitions which does exhibits conductivity-like behavior as the temperature, ( T ). Our results reveal that damping remains stronger than in 2DEG due to the persistent influence of cubic RSOC. The interplay between RSOC and magnon absorption broadens the spectral response, with the damping peak shifting more notably at higher temperatures. Stronger RSOC expands the magnon interaction phase space, thus widening the damping spectrum. A key observation emerges with the Fermi level ((E_f)): a finite (E_f) sustains spin imbalance and enhances damping, whereas (E_f = 0) suppresses it, unlike in 2DEG. The electric field tunability of RSOC enables real-time control over spin relaxation and angular momentum transfer, offering a pathway toward voltage-controlled spintronic devices. These findings highlight the superior potential of 2DHG for tailoring spin dynamics via electric and thermal effects.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
11 pages, 7 figures
Phase-change materials for volatile threshold resistive switching and neuronal device applications
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Huandong Chen, Jayakanth Ravichandran
Volatile threshold resistive switching and neuronal oscillations in phase-change materials, specifically those undergoing metal-to-insulator and charge density wave transitions, offer unique attributes such as fast and low-field volatile switching, tunability, and non-linear behaviors. These characteristics are particularly promising for emulating neuronal behavior and thus hold great potential for realizing energy-efficient neuromorphic computing. In this review, we summarize recent advances in the development of neuronal oscillator devices based on three archetypal electronic phase-change materials: the correlated oxide VO2, the charge density wave transition metal dichalcogenide 1T-TaS2, and the emerging phase-change chalcogenide perovskite BaTiS3. We discuss progress from the perspective of materials development, including structural phase transitions, synthesis methods, electrical properties, and device implementation. Finally, we emphasize the major challenges that must be addressed for practical applications of these phase-change materials and provide our outlook on the future research directions in this rapidly evolving field.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
Observation of the Dirac Dispersions in Co-doped CaFe2As2
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-18 20:00 EST
Marcin Rosmus, Natalia Olszowska, Rafal Kurleto, Zbigniew Bukowski, Pawel Starowicz
We performed an angle-resolved photoemission spectroscopy (ARPES) study of the electronic structure of the CaFe2As2 122-iron pnictide, a parent compound, and two iron-based superconductors CaFe(2-x)CoxAs2 (x = 0.07 and 0.15). We studied the band structure of this system across the phase diagram with the transition from the orthorhombic spin density wave (SDW) phase to the tetragonal paramagnetic phase. We observed characteristic features of the electronic structures corresponding to the antiferromagnetic phase in the parent compound and the samples with low cobalt concentration (x = 0.07). For highly doped systems (x = 0.15), the measurements revealed the concentric branches of the Fermi surface, which are associated with paramagnetic and superconducting 122-iron pnictides. We found the existence of Dirac cones located at 30 meV below Fermi energy for nonsuperconducting CaFe2As2 and superconducting CaFe(1.93)Co(0.07)As2 orthorhombic SDW systems.
Superconductivity (cond-mat.supr-con)
Rosmus, M.; Olszowska, N.; Kurleto, R.; Bukowski, Z.; Starowicz, P. Observation of the Dirac Dispersions in Co-Doped CaFe2As2. J. Phys. Chem. C 2025
Anatomy of anomalous Hall effect due to magnetic fluctuations
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Ola Kenji Forslund, Xiaoxiong Liu, Soohyeon Shin, Chun Lin, Masafumi Horio, Qisi Wang, Kevin Kramer, Saumya Mukherjee, Timur Kim, Cephise Cacho, Chennan Wang, Tian Shang, Victor Ukleev, Jonathan S. White, Pascal Puphal, Yasmine Sassa, Ekaterina Pomjakushina, Titus Neupert, Johan Chang
The anomalous Hall { e}ffect (AHE) has emerged as a key indicator of time-reversal symmetry breaking (TRSB) and topological features in electronic band structures. Absent of a magnetic field, the AHE requires spontaneous TRSB but has proven hard to probe due to averaging over domains. The anomalous component of the Hall effect is thus frequently derived from extrapolating the magnetic field dependence of the Hall response. We show that discerning whether the AHE is an intrinsic property of the field free system becomes intricate in the presence of strong magnetic fluctuations. {As a study case,} we use the Weyl semimetal PrAlGe, where TRSB can be toggled via a ferromagnetic transition, providing a transparent view of the AHE's topological origin. Through a combination of thermodynamic, transport and muon spin relaxation measurements, we contrast the behaviour below the ferromagnetic transition temperature to that of strong magnetic fluctuations above. Our results {on PrAlGe provide general insights into the} interpretation of anomalous Hall signals in systems where TRSB is debated, such as families of Kagome metals or certain transition metal dichalcogenides.
Strongly Correlated Electrons (cond-mat.str-el)
8 pages, 5 figures
Superconducting and spin-density wave phases probed by scanning tunneling spectroscopy in the organic conductor \(\mathrm{(TMTSF)_{2}ClO_{4}}\)
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-18 20:00 EST
Mohammadmehdi Torkzadeh, Pascale Senzier, Claude Bourbonnais, Abdelouahab Sedeki, Cécile Méziere, Marie Hervé, Francois Debontridder, Pascal David, Tristan Cren, Claire Marrache-Kikuchi, Denis Jerome, Christophe Brun
By scanning tunneling microscopy (STM) we have probed the local quasi-particle density of states (DOS) of the Bechgaard salt organic superconductor \(\mathrm{(TMTSF)_{2}ClO_{4}}\) in slowly cooled single crystals cleaved under ultrahigh vacuum conditions. In well STM imaged crystallographic surface planes, the local DOS has been probed for different surface areas at temperatures above and below the critical temperature of superconducting or insulating spin-density wave states. While a rather homogeneous superconducting state is expected in the bulk from previous studies, depending on the degree of disorder introduced by cleavage in the anion lattice, an inhomogeneous granular state is predominantly observed at the surface. A pronounced linear V-shape profile of the local DOS is observed from intermediate to the lowest energy scale in the less disordered superconducting surface areas. This supports the existence of an unconventional d-wave like order parameter with nodes at low energy, which is preceded by more energetic fluctuations attributed to quantum criticality of the material. At higher energy disorder combined to correlations deplete further the DOS. By contrast a non-linear U-shape characterizes the local low energy DOS profile for the more disordered and insulating surface areas of the spin-density wave state. The experimental results are compared quantitatively with those predicted by the renormalization group theory of the quasi-one dimensional electron gas model and its description of the superconducting and spin-density wave states that are interlinked by quantum criticality in the Bechgaard salts.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
10 pages, 6 figures
Superconducting Diode Effects: Mechanisms, Materials and Applications
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-18 20:00 EST
Jiajun Ma, Ruiya Zhan, Xiao Lin
Superconducting diode effects (SDEs) generally emerge in superconducting systems where both time-reversal and inversion symmetries are broken, showing nonreciprocal current characteristics: nondissipative in one direction and ohmic in the opposite. Since the discovery of the SDEs by Ando et al. in the noncentrosymmetric superconductor [Nb/V/Ta]n in 2020, notable progress has been achieved on both the theoretical and experimental fronts. It has been proposed that intrinsic SDEs are closely linked to various exotic superconducting states, such as the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, topological superconductivity, and chiral superconductivity. Recently, SDEs have emerged as important experimental tools for detecting symmetry breaking in exotic superconducting states. This advancement not only enhances our understanding of the fundamental nature of SDEs but also opens new possibilities for their applications in superconducting physics and related fields. This review focuses on the recent experimental progress in the observation of the SDEs and discusses their primary mechanisms from the perspective of material properties and symmetry breaking. Finally, we summarize the observed rectification efficiency of SDE devices and discuss future research directions in this rapidly developing field.
Superconductivity (cond-mat.supr-con)
17 pages, 8 figures, published to Adv. Phys. Res
Advanced Ahysics Research,2025,2400180
Rheological response of soft Solid/Liquid Composites
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-18 20:00 EST
Elina Gilbert, Christophe Poulard, Anniina Salonen
Understanding a material's dissipative response is important for their use in many applications, such as adhesion. In dispersions the interplay between matrix and inclusions complicates any description. Fractional rheology is conveniently used to fit the storage and loss moduli of complex materials, although the physical picture is often elusive. We study the rheology of soft solid/liquid composites of liquid poly(ethylene glycol) (PEG) droplets in a soft poly(dimethylsiloxane) (PDMS) matrix. We analyze the influence of the droplets through fractional rheology and a time-concentration superposition. Viscous dissipation increases proportionally with volume fraction, and we show that a simple, well-fitting model can induce misinterpretation of the physics in a complex material.
Soft Condensed Matter (cond-mat.soft)
10 pages, 5 figures, submitted to PNAS
New insights into crystallographic relation and lattice dynamics effects in {CdO/MgO} superlattices grown by plasma-assisted molecular beam epitaxy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Aleksandra Wierzbicka, Ewa Przezdziecka, Igor Perlikowski, Eunika Zielony, Abinash Adhikari, Anastasiia Lysak
This article explores the structural properties of molecular beam epitaxy grown {CdO/MgO} superlattices on sapphire substrates of different crystallographic orientations (a-, c-, r-, and m-plane). The investigations involve a comprehensive analysis using X-ray diffraction and Raman spectroscopy. High-resolution X-ray diffraction studies unveil a significant influence of surface symmetry on both the substrates and the epitaxial layers, particularly with respect to the occurrence of twins in the superlattices. Remarkably, no twins are observed on r-oriented sapphire substrates, resulting in improved interface and crystallographic quality. The results of studies demonstrated in this work show that the growth rate of CdO sublayers within {CdO/MgO} superlattices is intricately dependent on the substrate orientation. Notably, the c-plane and m-plane sapphire substrates yielded thicker CdO sublayers, indicating comparable growth rates for these crystallographic orientations. Conversely, the a-plane and r-plane orientations seemed to favor a slower growth rate of CdO sublayers.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
24 pages, 8 figures,
Structural and Electronic Properties of Ta2O5 with One Formula Unit
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Yangwu Tong, Huimin Tang, Yong Yang
Based on particle swarm optimization (PSO) algorithm and density functional theory (DFT) calculations, we identify a stable triclinic crystal structure of Ta2O5 (named as {}1-Ta2O5) at atmospheric pressure whose unit cell contains one formula unit (Z=1). Comparison with the Z=1 Ta2O5 structures from the Materials Project [APL Mater. 1, 011002 (2013)] reveals that {}1-Ta2O5 is energetically the most stable among the Z=1 Ta2O5 phases, and is the second most stable among all the Ta2O5 phases. Characterization of {}1-Ta2O5 is carried out by analyzing the X-ray powder diffraction patterns, the elastic, vibrational, thermal and electronic properties. The electronic structures of {}1-Ta2O5 are calculated using standard DFT as well as many-body perturbation theory within the GW approximation. The results indicate that {}1-Ta2O5 is a wide band gap semiconductor with an indirect gap of ~ 3.361 eV.
Materials Science (cond-mat.mtrl-sci)
25 pages, 5 figures, 3 tables
Computational Materials Science 230, 112482 (2023)
Layer-Resolved Quantum Transport in Twisted Bilayer Graphene: Counterflow and Machine Learning Predictions
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Matheus H. Gobbo Khun, L. A. Silva, D. A. Bahamon
The layer-resolved quantum transport response of a twisted bilayer graphene device is investigated by driving a current through the bottom layer and measuring the induced voltage in the top layer. Devices with four- and eight-layer differentiated contacts were analyzed, revealing that in a nanoribbon geometry (four contacts), a counterflow current emerges in the top layer, while in a square-junction configuration (eight contacts), this counterflow is accompanied by a transverse, or Hall, component. These effects persist despite weak coupling to contacts, onsite disorder, and variations in device size. The observed counterflow response indicates a circulating interlayer current, which generates an in-plane magnetic moment excited by the injected current. Finally, due to the intricate relationship between the electrical layer response, energy, and twist angle, a clusterized machine learning model was trained, validated, and tested to predict various conductances.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
12 pages and 9 figures
A square skyrmion lattice in multi-orbital \(f\)-electron systems
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
We report the emergence of a square-shaped skyrmion lattice in multi-orbital \(f\)-electron systems with easy-axis magnetic anisotropy on a centrosymmetric square lattice. By performing mean-field calculations for an effective localized model consisting of two Kramers doublets, we construct the low-temperature phase diagram in a static external magnetic field. Consequently, we find that a square-shaped skyrmion lattice with the skyrmion number of one appears in the intermediate-field region when the crystal field splitting between the two doublets is small. Furthermore, we identify another double-\(Q\) state with a nonzero net scalar chirality at zero- and low-field regions, which is attributed to the help of the multi-orbital degree of freedom. Our results offer another route to search for skyrmion-hosting materials in centrosymmetric \(f\)-electron tetragonal systems with multi-orbital degrees of freedom, e.g., Ce-based compounds. This contrasts with conventional other \(f\)-electron systems hosting skyrmion lattices, such as Gd- and Eu-based compounds without orbital angular momentum.
Strongly Correlated Electrons (cond-mat.str-el)
Quantum Tunneling Enhanced Hydrogen Desorption from Graphene Surface: Atomic versus Molecular Mechanism
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
We study the desorption mechanism of hydrogen isotopes from graphene surface using first-principles calculations, with focus on the effects of quantum tunneling. At low temperatures, quantum tunneling plays a dominant role in the desorption process of both hydrogen monomers and dimers. In the case of dimer desorption, two types of mechanisms, namely the traditional one-step desorption in the form of molecules (molecular mechanism), and the two-step desorption in the form of individual atoms (atomic mechanism) are studied and compared. For the ortho-dimers, the dominant desorption mechanism is found to switch from the molecular mechanism to the atomic mechanism above a critical temperature, which is respectively ~ 300 K and 200 K for H and D.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
25 pages, 4 figures, 2 tables
Chinese Physics Letters 41, 086801 (2024)
Surface magnetoelectric driven spin dynamics in metallic antiferromagnets
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
R.M. Dubrovin, A.V. Kimel, A.K. Zvezdin
Although magnetoelectric effects in metals are usually neglected, assuming that applied electric fields are screened by free charge carriers, the skin depth, defining the penetration depth of the fields, is non-zero and for THz electric fields typically reaches 400 nm. Hence, if the thickness of an antiferromagnetic film is of the order of tens of nm, electric field induced effects cannot be neglected. Here, we theoretically study the THz electric field induced spin dynamics in the metallic antiferromagnets \(\mathrm{Mn}_{2}\mathrm{Au}\) and \(\mathrm{CuMnAs}\), whose spin arrangements allow them to exhibit a linear magnetoelectric effect. We shown that the THz magnetoelectric torque in metallic antiferromagnets is proportional to the time derivative of the THz electric field induced polarization. Our simulations reveal that the magnetoelectric driven spin dynamics is indeed not negligible and can fairly explain the previously published experimental results on antiferromagnetic dynamics excited by the THz pump pulses in \(\mathrm{Mn}_{2}\mathrm{Au}\) at the corresponding magnetoelectric susceptibility value \(\alpha_{\mathrm{ME}} \simeq 2 \times 10^{-5}\) without involving other mechanisms. This value is about one order of magnitude smaller than that known for collinear and rare-earth-free antiferromagnets such as \(\mathrm{Cr}_{2}\mathrm{O}_{3}\). For such a value of magnetoelectric response, it appears that the THz electric fields of realistic strengths of about 1 MV/cm are sufficient in order to achieve spin dynamics with the amplitudes sufficiently strong enough for switching of the antiferromagnetic Néel vector between the stable ground states. Thus, we contend that the experimental studies of the coherent dynamics of the antiferromagnetic Néel vector driven by the THz pulses in magnetoelectric metal films necessitate a careful consideration of the linear magnetoelectric effect.
Materials Science (cond-mat.mtrl-sci)
10 pages, 5 figures
Finite-time blowup of a Brownian particle in a repulsive potential
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-18 20:00 EST
P. L. Krapivsky, Baruch Meerson
We consider a Brownian particle performing an overdamped motion in a power-law repulsive potential. If the potential grows with the distance faster than quadratically, the particle escapes to infinity in a finite time. We determine the average blowup time and study the probability distribution of the blowup time. In particular, we show that the long-time tail of this probability distribution decays purely exponentially, while the short-time tail exhibits an essential singularity. These qualitative features turn out to be quite universal, as they occur for all rapidly growing power-law potentials in arbitrary spatial dimensions. The quartic potential is especially tractable, and we analyze it in more detail.
Statistical Mechanics (cond-mat.stat-mech), Mathematical Physics (math-ph), Probability (math.PR)
12 pages, 13 figures
Exploring Novel 2D Analogues of Goldene: Electronic, Mechanical, and Optical Properties of Silverene and Copperene
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Emanuel J. A. dos Santos, Rodrigo A. F. Alves, Alexandre C. Dias, Marcelo L. Pereira Junior, Douglas S. Galvão, Luiz A. Ribeiro Junior
Two-dimensional (2D) materials have garnered significant attention due to their unique properties and broad application potential. Building on the success of goldene, a monolayer lattice of gold atoms, we explore its proposed silver and copper analogs, silverene and copperene, using density functional theory calculations. Our findings reveal that silverene and copperene are energetically stable, with formation energies of -2.3 eV/atom and -3.1 eV/atom, closely matching goldene's -2.9 eV/atom. Phonon dispersion and ab initio molecular dynamics simulations confirm their structural and dynamical stability at room temperature, showing no bond breaking or structural reconfiguration. Mechanical analyses indicate isotropy, with Young's moduli of 73 N/m, 44 N/m, and 59 N/m for goldene, silverene, and copperene, respectively, alongside Poisson's ratios of 0.46, 0.42, and 0.41. These results suggest comparable rigidity and deformation characteristics. Electronic band structure analysis highlights their metallic nature, with variations in the band profiles at negative energy levels. Despite their metallic character, these materials exhibit optical properties akin to semiconductors, pointing to potential applications in optoelectronics.
Materials Science (cond-mat.mtrl-sci)
24 pages and six figures
Exerting chemical pressure on the kagome lattice as frustration control in the kapellasite family \(A\)Cu\(_3\)(OH)\(_{6+x}\)(Cl,Br)\(_{3-x}\)
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Jonas Andreas Krieger, Thomas James Hicken, Hubertus Luetkens, Reinhard K. Kremer, Pascal Puphal
The kapellasite family \(A\)Cu\(_3\)(OH)\(_{6+x}\)(Cl,Br)\(_{3-x}\) forms a series of compounds, wherein the chemical pressure realized by the \(A-\)site cation tunes the spin exchange in the frustrated distorted kagome lattice. Via hydrothermal synthesis we have grown single crystals of the whole series for \(A=\) rare-earths and found a clear structural transition to a superstructure variant at a specific chemical pressure level exerted by \(A\)=Dy. Phases with crystal structures in the vicinity of this superstructure transition realize a distorted kagome lattice of the Cu\(^{2+}\) cations with characteristic features of a spin liquid. Here, subtle structural disorder as well as controlled chemical pressure can stabilize the spin liquid phase. We study the crystal structure and the magnetic ground state of these phases via single crystal x-ray diffraction, magnetic susceptibility, specific heat and muon spin spectroscopy measurements.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Evolution of radiation-induced damage in nuclear graphite - a comparative structural and microstructural study
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Magdalena Wilczopolska, Kinga Suchorab, Magdalena Gaweda, Malgorzata Frelek-Kozak, Pawel Ciepielewski, Marcin Brykala, Wojciech Chmurzynski, Iwona Jozwik
Graphite, as a material for high-temperature gas-cooled reactors (HTGR), will be exposed to harsh environment. The stability of graphite structure under irradiation is of a key importance for efficiency, reliability and security of the Generation IV nuclear reactors. Three types of nuclear grade graphite were subjected to irradiation in this research - two commercially manufactured (IG-110 and NBG-17) and the laboratory's in-home material (NCBJ). The samples were exposed to 150 keV Ar+ and He+ ions bombardment at 400 C with fluences ranging from 1E12 to 2E17 ion/cm2 in order to simulate in-reactor conditions. For analysis of the level of structure damage, type of created defects and crystallite size changes under ion irradiation ex-situ Raman spectroscopy was used. The methodology of spectra fitting was developed. Furthermore, SEM observation of irradiated materials was performed. Results showed structural degradation of materials by the means of amorphisation: slight at a low fluence level, rising rapidly at higher irradiation values. Furthermore, stronger structural disorder was found in the materials irradiated with heavier Ar+ ions than with lighter He+. Microstructural evolution of the nuclear graphites aligned with the structural deterioration in its stepwise character.
Materials Science (cond-mat.mtrl-sci)
Diffusive spin transport of the spin-1/2 XXZ chain in the Ising regime at zero magnetic field and finite temperature
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Jose M. P. Carmelo, Pedro D. Sacramento
The studies of this paper on the spin-1/2 XXZ chain at finite temperatures T>0 have two complementary goals. The first is to identify the spin carriers of all its Sq>0 energy eigenstates and to show that their spin elementary currents fully control the spin-transport quantities. Here Sq is the q-spin of the continuous SUq(2) symmetry of the model for anisotropy >1. To achieve this goal, our studies rely on a suitable exact physical-spin this http URL the spin stiffness and the zero-field spin-diffusion constant are expressed in terms of thermal expectation values of the square of the elementary currents carried by the spin carriers. Our second goal is to confirm that the zero-field and finite-temperature spin transport is normal diffusive for anisotropy >1. We use two complementary methods that rely on an inequality for the T>0 spin stiffness and the above thermal expectation values, respectively, to show that the contributions to ballistic spin transport vanish. Complementarily, for T>0 and anisotropy >1, the spin-diffusion constant is found to be finite and enhanced upon lowering T, reaching its largest yet finite values at low temperatures. Evidence suggests that it diverges in the anisotropy limit to 1 for T>0, consistent with T>0 anomalous superdiffusive spin transport at anisotropy 1 and zero field.
Strongly Correlated Electrons (cond-mat.str-el)
31 pages, 6 figures, accepted for publication in Physical Review Ressearch
When Adiabaticity Is Not Enough to Study Topological Phases in Solid-State Physics: Comparing the Berry and Aharonov-Anandan Phases in 2D Materials
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Abdiel de Jesús Espinosa-Champo, Alejandro Kunold, Gerardo G. Naumis
Topological phases arise as the parameters of a quantum system are varied as a function of time. Under the adiabatic approximation, the time dependency can be removed and the Berry topological phase can be obtained from a trajectory on the parameter space. Although this approach is usually applied in solid-state physics without further reflection, in many cases, say in Dirac or Weyl materials, the adiabatic approximation is never met as many systems are gapless. Here it is shown how to use other time dependent defined topological quantities, in particular the Aharonov-Anandan phase that provides information not only about the topology but also about band transitions. Therefore, we analyze the problem of graphene under electromagnetic radiation from a time-driven perspective, demonstrating how the Aharonov-Anandan and Berry phases provide complementary information about the topology and interband transitions. This is achieved using the Dirac-Bloch formalism and by solving the time-dependent equations within Floquet theory.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
13 pages, 7 figures
Magnetization symmetry for the MnTe altermagnetic candidate
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
N.N. Orlova, V.D. Esin, A.V. Timonina, N.N. Kolesnikov, E.V. Deviatov
We experimentally investigate the magnetization angle dependence \(M(\alpha)\) for single crystals of MnTe altermagnetic candidate. In high magnetic fields, experimental \(M(\alpha)\) curves nearly independent of temperature, they mostly reflect standard antiferromagnetic spin-flop processes below the Néel vector reorientation field. In contrast, \(M(\alpha)\) dependences are quite unusual at low temperatures and in low magnetic fields: below 81~K, spontaneous magnetization appears as a sharp \(M(T)\) magnetization jump, the easy axis direction is equally \(\pi/2\) rotated either by increasing the field above 1~kOe or the temperature above 81~K. We provide experimental arguments that the spontaneous magnetization of MnTe below 81~K differs strongly from the well known weak ferromagnetism of conventional antiferromagnetics, thus, it requires to take into account formation of the altermagnetic ground state. Despite the MnTe altermagnetic state is expected to be g-wave, i.e. \(\pi/3\) periodic one, our experiment confirms the prevailing population of one from three easy axes, as it has been shown previously by temperature-dependent angle-resolved photo-emission spectroscopy.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
AI-guided transition path sampling of lipid flip-flop and membrane nanoporation
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-18 20:00 EST
We study lipid translocation ("flip-flop") between the leaflets of a planar lipid bilayer with transition path sampling (TPS). Rare flip-flops compete with biological machineries that actively establish asymmetric lipid compositions. Artificial Intelligence (AI) guided TPS captures flip-flop without biasing the dynamics by initializing molecular dynamics simulations close to the tipping point, i.e., where it is equally likely for a lipid to next go to one or the other leaflet. We train a neural network model on the fly to predict the respective probability, i.e., the "committor" encoding the mechanism of flip-flop. Whereas coarse-grained DMPC lipids "tunnel" through the hydrophobic bilayer, unaided by water, atomistic DMPC lipids instead utilize spontaneously formed water nanopores to traverse to the other side. For longer DSPC lipids, these membrane defects are less stable, with lipid transfer along transient water threads in a locally thinned membrane emerging as a third distinct mechanism. Remarkably, in the high (~660) dimensional feature space of the deep neural networks, the reaction coordinate becomes effectively linear, in line with Cover's theorem and consistent with the idea of dominant reaction tubes.
Soft Condensed Matter (cond-mat.soft), Biomolecules (q-bio.BM)
Uncovering the atomic structure of substitutional platinum dopants in MoS\(_2\) with single-sideband ptychography
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
David Lamprecht, Anna Benzer, Manuel Längle, Mate Capin, Clemens Mangler, Toma Susi, Lado Filipovic, Jani Kotakoski
We substitute individual Pt atoms into monolayer MoS\(_2\) and study the resulting atomic structures with single-sideband (SSB) ptychography supported by ab initio simulations. We demonstrate that while high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) imaging provides excellent Z-contrast, distinguishing some defect types such as single and double sulfur vacancies remains challenging due to their low relative contrast difference. However, SSB with its nearly linear Z-contrast and high phase sensitivity enables reliable identification of these defect configurations as well as various Pt dopant structures at significantly lower electron doses. Our findings uncover the precise atomic placement and highlight the potential of SSB ptychography for detailed structural analysis of dopant-modified 2D materials while minimizing beam-induced damage, offering new pathways for understanding and engineering atomic-scale features in 2D systems.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Effective field theory and thermal Hall effect of magnons in square-lattice antiferromagnets
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Thermal Hall transport has emerged as a powerful probe of neutral quasiparticles and associated gauge fields in insulating materials. Although the emergence of a thermal Hall effect is known to be sensitive to lattice geometry and gauge structures, an intuitive understanding of the conditions for its emergence remains limited, especially for edge-shared lattice geometries such as square and triangular lattices. Here, we develop an effective field theory of magnons in square-lattice antiferromagnets to establish the intuitive picture that elucidates the conditions for a finite thermal Hall response. By constructing an effective field theory from a spin model on the square lattice, we show that its low-energy excitations can be described by magnons with an effective SU(2) gauge field and Zeeman field that couple to magnon's pseudospins, which reflect the two-sublattice degrees of freedom in the antiferromagnets. The field strength associated with the SU(2) gauge field acts as a pseudospin-dependent magnetic field, bending the magnon's trajectories in opposite directions depending on their pseudospin. In addition, the effective Zeeman field induces an imbalance between pseudospin up and down magnons, and the combination of these two fields gives rise to the thermal Hall effect of magnons. This intuitive picture provides a systematic classification of magnetic orders in square-lattice antiferromagnets based on the presence or absence of the thermal Hall effect. We expect that our framework can be extended to various other spin models.
Strongly Correlated Electrons (cond-mat.str-el)
9 pages, 1 figure
Asymmetric simple exclusion process on a random comb: Transport properties in the stationary state
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-18 20:00 EST
We address the dynamics of interacting particles on a disordered lattice formed by a random comb. The dynamics comprises that of the asymmetric simple exclusion process, whereby motion to nearest-neighour sites that are empty are more likely in the direction of a bias than in the opposite direction. The random comb comprises a backbone lattice from each site of which emanates a branch with a random number of sites. The backbone and the branches run in the direction of the bias. The number of branch sites or alternatively the branch lengths are sampled independently from a common distribution, specifically, an exponential distribution. The system relaxes at long times into a nonequilibrium stationary state. We analyse the stationary-state density of sites across the random comb by employing a mean-field approximation. Further, we explore the transport properties, in particular, the stationary-state drift velocity of particles along the backbone. We show that in the stationary state, the density is uniform along the backbone and nonuniform along the branches, decreasing monotonically from the free-end of a branch to its intersection with the backbone. On the other hand, the drift velocity as a function of the bias strength has a non-monotonic dependence, first increasing and then decreasing with increase of bias. However, remarkably, as the particle density increases, the dependence becomes no more non-monotonic. We understand this effect as a consequence of an interplay between biased hopping and hard-core exclusion, whereby sites towards the free end of the branches remain occupied for long times and become effectively non-participatory in the dynamics of the system. This results in an effective reduction of the branch lengths and a motion of the particles that takes place primarily along the backbone.
Statistical Mechanics (cond-mat.stat-mech)
20 pages, 4 figures
Single-Molecule Water Motion on h-BN and Graphene: A Paradigm Shift in Understanding the Behaviour of Water on 2D Material Interfaces
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Philipp Seiler, Anthony Payne, Neubi F. Xavier Jr, Louie Slocombe, Marco Sacchi, Anton Tamtögl
Understanding water behaviour on 2D materials is crucial for sensing, microfluidics, and tribology. While water/graphene interactions are well studied, water on hexagonal boron nitride (h-BN) remains largely unexplored. Despite structural similarity to graphene, h-BN's slightly polar B-N bonds impart a large band gap, high thermal conductivity, and chemical stability, making it promising for electronics, lubricants, and coatings. Moreover, existing water studies often focus on multilayer water dynamics, overlooking single-molecular details. We bridge this gap by studying single-molecular water friction and diffusion on h-BN, comparing it with graphene using helium spin-echo experiments and ab initio calculations. Our findings show that water diffusion on h-BN/Ni follows a complex rotational-translational dynamic, unlike graphene. While conventional views treat water motion as discrete jumps between equivalent adsorption sites, we demonstrate that on h-BN, water molecules rotate freely around their centre of mass. Although the binding energies of water on h-BN and graphene are similar, the activation energy for water dynamics on h-BN is 2.5 times lower than on graphene, implying a much lower barrier for molecular mobility. The fundamentally different diffusion characteristics which classical models cannot capture, underscores the need to rethink how we model water on polar 2D materials. Moreover, our analysis reveals that the metal substrate strongly influences water friction, with h-BN/Ni showing a markedly lower friction than graphene/Ni, in stark contrast to the free-standing materials. These findings challenge assumptions about 2D material-water interactions, highlighting the crucial role of substrate effects in chemistry and material science and offer insights for designing next-generation microfluidic devices that require precise water mobility control.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Effective medium theory for the electrical conductivity of random metallic nanowire networks
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-02-18 20:00 EST
Yuri Yu. Tarasevich, Irina V. Vodolazskaya, Andrei V. Eserkepov
Interest in studying the conductive properties of networks made from randomly distributed nanowires is due to their numerous technological applications. Although the sheet resistance of such networks can be calculated directly, the calculations require many characteristics of the system (distributions of lengths, diameters and resistances of nanowires, distribution of junction resistance), the measurement of which is difficult. Furthermore, such calculations can hardly offer an analytical dependence of the sheet resistance on the basic physical parameters of the systems under consideration. Although various theoretical approaches offer such analytical dependencies, they are often based on more or less reasonable assumptions rather than rigorously proven statements. Here, we offer an approach based on Foster's theorem to reveal a dependence of the sheet resistance of dense nanowire networks on the main parameters of such networks. This theorem offers an additional perspective on the effective medium theory and extends our insight.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
7 pages, 4 figs, 2 tables, 34 refs
Weyl and Dirac Semimetals for Thermoelectric Applications
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Saurabh Singh, Sarmistha Das, Shiv Kumar
Weyl and Dirac semimetals, characterized by their unique band structures with linear energy dispersion (E vs k) near the Fermi level (EF), have emerged as promising candidates for next-generation technology based on thermoelectric materials. Their exceptional electronic properties, notably high carrier mobility and substantial Berry curvature, offer the potential to surmount the limitations inherent in conventional thermoelectric materials. A comprehensive understanding of the fundamental physics underlying these materials is essential. This chapter mainly focused into the topological properties and distinctive electronic band structures of Weyl and Dirac semimetals, providing a theoretical framework for comprehending their thermoelectric transport properties such as Seebeck coefficients, electrical and thermal conductivity. The pivotal role of Berry curvature in enhancing Seebeck coefficients while reducing thermal conductivity is a key focus. Experimental advancements in synthesizing single crystals and characterizing these materials have been significant. Recent development in material growth and characterization techniques have propelled research forward. The intricate relationship between material properties, such as carrier concentration, electronic bandgap, and crystal structure, and thermoelectric performance is explored. Realizing the potential of Weyl and Dirac semimetals for practical thermoelectric applications necessitates overcoming specific challenges. This chapter outlines strategies to optimize thermoelectric figures of merit (ZT) through band engineering, carrier doping, and nanostructuring. Moreover, the exploration of hybrid materials and heterostructures offers promising avenues for enhancing thermoelectric performance for renewable energy applications.
Materials Science (cond-mat.mtrl-sci)
23 pages, 8 figures
Floquet topological state induced by light-driven band inversion in SnTe
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
F.Chassot, G. Kremer, A. Pulkkinen, C. Wang, J. Krempasky, J. Minar, G. Springholz, M. Puppin, J.H. Dil, C. Monney
High intensity coherent light can dress matter, realizing new hybrid phases that are not accessible in equilibrium. This effect results from the coherent interaction between Bloch states inside the solid and the periodic field of impinging photons which produces hybrid light-matter states called Floquet-Bloch states that can alter properties of the solid. Optically inducing a topological state in a semiconductor using so-called Floquet engineering is an exciting prospect. However, it has not been realized, despite its theoretical prediction more than 10 years ago. Here we show that an ultrashort-lived topological state that is absent at equilibrium in the ground state of SnTe can be created with femtosecond light pulses. This occurs when the photoexcitation is similar in energy with the band gap of this polar semiconductor. We observe a concomitant renormalization of the band dispersions that reveals the generation of Floquet states connecting to the topological state. We therefore provide the first direct experimental observation of a Floquet topological state and propose that it is driven by a light-induced band inversion in SnTe. Our discovery opens the way for controlling optically on-demand the topological properties of semiconductors.
Strongly Correlated Electrons (cond-mat.str-el)
18 pages, 12 figures
Identification of Polytypism and Their Dislocations in Bilayer MoS2 Using Correlative Transmission Electron Microscopy and Raman Spectroscopy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Xin Zhou, Tobias Dierke, Mingjian Wu, Shengbo You, Klaus Götz, Tobias Unruh, Philipp Pelz, Johannes Will, Janina Maultzsch, Erdmann Spiecker
Stacking orders and topological defects substantially influence the physical properties of 2D van der Waals (vdW) materials. However, the inherent features of 2D materials challenge the effectiveness of single characterization techniques in identifying stacking sequences, necessitating correlative approaches. Using bilayer MoS2 as a benchmark, we differentiate its polytypism and specific dislocations through transmission electron microscopy (TEM) and Raman spectroscopy. Perfect and partial dislocations were revealed in TEM, which are closely linked to the stacking sequences, thus indirectly indicating the 2H and 3R polytypes. 3D electron diffraction reconstruction on relrods and low-frequency Raman spectroscopy further validated these polytypes owing to their reliance on crystal symmetry. Surprisingly, we unexpectedly resolved both polytypes despite starting with 2H bulk crystal, pointing to a possible phase transition during mechanical exfoliation. The correlative TEM-Raman approach can be extended to other 2D materials, paving the way for property alteration via stacking and defect engineering.
Materials Science (cond-mat.mtrl-sci)
13 pages, 3 figures
Enhanced magnetoelastic stress in disordered iron-gallium alloy thin films revealed by direct measurement
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Adrián Begué, Maria Grazia Proietti, José Ignacio Arnaudas, Miguel Ciria
The large magnetostriction in FeGa alloys is relevant for manifold applications, but for thin films, it can play a prominent role in controlling the strength of the magnetic anisotropy. Bulk samples show values depending on the extensive preparation procedure compendium, which is limited in its temperature range for high-quality thin-film synthesis. Here, we present a study of the magnetoelastic coupling coefficients \(B_1\) and \(B_2\) in epitaxial FeGa thin films below 50 nm deposited on the MgO(001) surface at 150 \(^\circ\)C by the cantilever method. Series of films with 22, 28, and 33 at. % Ga do not show thickness-dependent variations for \(B_1\) and \(B_2\), but \(-B_1\) for the 22 at. % Ga composition is 10 MPa, roughly 2 times the bulk value and smaller than the bulk-like value of \(-B_1\)=12.1 MPa obtained for a film with 17 at. % Ga. This enhancement is correlated with the A2 crystal structure for the film rather than the coexistence with D0\(_3\) or other ordered nanometric precipitates proposed for bulk samples. Synchrotron diffraction excludes the formation of long-range L6\(_0\), or D0\(_3\) precipitates in samples with (001)A2 peaks at concentrations around 25 at. % Ga, which implies partial chemical disorder. The analysis of extended x-ray absorption fine structure measurements points to a D0\(_3\) local order with a residual number of Ga-Ga pairs. Considering that the substrate quenches the movable strain in the A2 phase described in dual-phase structures, our results point to the important role of the electronic structure of the iron atoms modified by the presence of Ga in the alloy. This effect enlarges \(B_1\) in films with the A2 phase, stabilized using epitaxial growth.
Materials Science (cond-mat.mtrl-sci)
11 pages, 6 figures
Learning in a Multifield Coherent Ising Machine
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Daan de Bos, Marc Serra-Garcia
Physical information processors can learn from examples if they are modified according to an abstract parameter update equation, termed a learning rule. We introduce a physical model for self-learning that encodes the learning rule in the Hamiltonian of the system. The model consists of a network of multi-modal resonators. One of the modes is driven parametrically into a bi-stable regime, forming a coherent Ising machine (CIM) -- that provides the long-term memory that stores learned responses (weights). The CIM is augmented with an additional spinor field that acts as short-term (activation) memory. We numerically demonstrate that, in the presence of suitable nonlinear interactions between the long-term memory Ising machine and the short-term memory auxiliary field, the system autonomously learns from examples.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Disordered Systems and Neural Networks (cond-mat.dis-nn), Emerging Technologies (cs.ET), Neural and Evolutionary Computing (cs.NE), Adaptation and Self-Organizing Systems (nlin.AO)
8 pages, 4 figures
Review on thermoelectric properties of transition metal dichalcogenides
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
I. Pallecchi, N. Manca, B. Patil, L. Pellegrino, D. Marre'
Transition metal dichalcogenides (TMDs) are considered an advantageous alternative to their celebrated two-dimensional (2D) van der Waals akin compound, graphene, for a number of applications, especially those requiring a gapped and possibly tunable band structure. Thermoelectricity is one of the application fields where TMDs could indeed outperform graphene, thanks to their lower thermal conductivity, large effective masses, valley degeneracy, varied and tunable transport properties, as well as sensitivity of their band structures and phonon spectra to confinement. Yet, despite promising theoretical predictions, thermoelectric properties of TMDs have not been extensively investigated so far and a clear assessment of TMDs as viable thermoelectric materials, based on experimental results, is still missing. In this paper, we review the experimental findings of literature on thermoelectric properties of TMDs, to sort out the countless combinations of chemical compositions, doping, off-stoichiometry and sample forms which could potentially result in optimized and possibly competitive thermoelectric properties. Based on the experimental data of literature, we simulate the performance of an all-TMD thermoelectric device for practical application as a micron sized cryocooler or power generator.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Unformatted accepted manuscript
Nano Futures 4, 032008 (2020)
Spectral and Entanglement Transitions from Non-Hermitian Skin Pumping
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Non-Hermitian physics has unveiled unconventional spectral, topological and critical phenomena, challenging traditional band theories. This thesis advances its understanding in three aspects. First, the non-Hermitian skin effect (NHSE) is shown to protect real spectra in some ansatz models, not relying on crystal symmetries. Second, we discover the phenomenon of scaling-induced non-Hermitian exceptional criticality (SIEC), marked by a unconventional negative dip in entanglement entropy scaling, deviating from the well-established logarithmic behavior. A scaling-dependent generalized Brillouin zone (GBZ) is developed to analytically predict this SIEC. Third, we formulate a theoretical framework for phase-space GBZs, extending the concept of the GBZ to position-dependent systems, particularly for those with spatially inhomogeneous NHSE hoppings. Unprecedented phenomena, including GBZ bifurcation which also protects the stability of real spectra, are revealed, introducing new forms of topological robustness governed by phase-space GBZ bifurcations. This thesis also explores the NHSE in Bethe lattices, where the hyperbolic-like lattice geometry gives rise to a hierarchy of loop sizes that leads to new forms of critical NHSE behavior.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
PhD Thesis
Irreversible multi-band effects and Lifshitz transitions at the LaAlO3/SrTiO3 interface under field effect
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Ilaria Pallecchi, Nicolo' Lorenzini, Mian Akif Safeen, Musa Mutlu Can, Emiliano Di Gennaro, Fabio Miletto Granozio, Daniele Marre'
In this work, we investigate the irreversible effects of an applied electric field on the magnetotransport properties of LaAlO3/SrTiO3 conducting interfaces, with focus on their multiband character. We study samples of different types, namely with either crystalline or amorphous LaAlO3 overlayer. Our two-band analysis highlights the similarity of the electronic properties of crystalline and amorphous interfaces, regardless much different carrier densities and mobilities. Furthermore, filling and depletion of the two bands follow very similar patterns, at least in qualitative terms, in the two types of samples. In agreement with previous works on crystalline interfaces, we observe that an irreversible charge depletion takes place after application of a first positive back gate voltage step. Such charge depletion affects much more, in relative terms, the higher and three-dimensional dyz, dzx bands than the lower and bidimensional dxy, driving the system through the Lifshitz transition from two-band to single band behavior. The quantitative analysis of experimental data evidences the roles of disorder, apparent in the depletion regime, and temperature. Noteworthy, filling and depletion of the two bands follow very similar patterns in crystalline and amorphous samples, at least in qualitative terms, regardless much different carrier densities and mobilities.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Adv. Electron. Mater. 2021, 7, 2001120
The uncollapsed LaFe2As2 phase: compensated, highly doped, electron-phonon coupled, iron-based superconductor
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-18 20:00 EST
Ilaria Pallecchi, Akira Iyo, Hiraku Ogino, Marco Affronte, Marina Putti
The recently discovered LaFe2As2 superconducting compound, member of the 122 family of iron pnictide superconductors, becomes superconducting below Tc=13K, yet its nominal doping apparently places it in the extreme overdoped limit, where superconductivity should be suppressed. In this work, we investigate the normal state of magneto- and thermo-electric transport and specific heat of this compound. The experimental data are consistent with the presence of highly compensated electron and hole bands, with around 0.42 electrons per unit cell just above Tc, and high effective masses around 3m0. The temperature dependence of transport properties strongly resembles that of conventional superconductors, pointing to a key role of electron-phonon coupling. From these evidences, LaFe2As2 can be regarded as the connecting compound between unconventional and conventional superconductors.
Superconductivity (cond-mat.supr-con)
Phys. Rev. Materials 4, 114803 (2020)
Topology from Nothing
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-18 20:00 EST
Jacob R. Taylor, Sankar Das Sarma
Disorder remains a major obstacle to realizing topological Majorana zero modes (MZMs) in superconductor-semiconductor nanowires, and we show how deep learning can be used to recover topological MZMs mitigating disorder even when the pre-mitigation situation manifests no apparent topology. The disorder potential, as well as the scattering invariant (\(T_V\)) normally used to classify a device as topologically non-trivial are not directly measurable experimentally. Additionally, the conventional signatures of MZMs have proved insufficient due to their being accidentally replicated by disorder-induced trivial states. Recent advances in machine learning provide a novel method to solve these problems, allowing the underlying topology, suppressed by disorder, to be recovered using effective mitigation procedures. In this work, we leverage a vision transformer neural network trained on conductance measurements along with a CMA-ES optimization framework to dynamically tune gate voltages mitigating disorder effects. Unlike prior efforts that relied on indirect cost functions, our method directly optimizes \(T_V\) alongside additional local density of states-based topological indicators. Using a lightweight neural network variant, we demonstrate that even highly disordered nanowires initially lacking any topologically non-trivial regions can be transformed into robust topological devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Disordered Systems and Neural Networks (cond-mat.dis-nn)
14 figures, 10 pages
Resolving the sodiation process in hard carbon anodes with nanostructure specific X-ray imaging
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Martina Olsson, Antoine Klein, Nataliia Mozhzhukhina, Shizhao Xiong, Christian Appel, Mads Carlsen, Leonard Nielsen, Linnea Rensmo, Marianne Liebi, Aleksandar Matic
Hard carbons show significant promise as anode materials for sodium-ion batteries. However, monitoring the sodiation process in the hard carbon electrode during cycling and understanding the sodiation mechanism remain challenging. This article reports on operando 2D scanning small- and wide-angle X-ray scattering (SWAXS) and ex situ 3D SAXS tomography of hard carbon electrodes during the sodiation process. Structural changes are monitored with spatial and temporal resolution during the electrochemical process and shows that sodiation through micropore filling is the more dominating mechanism in the later stages of sodiation, i.e. in the plateau region of the voltage profile, while intercalation occurs continuously. Spatial inhomogeneities are resolved over the electrode and reveal an increased level of inhomogeneity at higher degree of sodiation with regions of different degrees of micropore filling. Resolving the processes spatially enables us to correlate plating, starting from the interface between the electrode and the current collector, to a higher degree of micropore filling. The work demonstrates how SWAXS imaging can contribute to understanding the sodiation of hard carbon anodes, not only by spatially resolved analysis, but also as a method to decouple contributions from different components in a cell, enabling more accurate scattering analysis in in situ environments.
Materials Science (cond-mat.mtrl-sci)
Correlative X-ray and electron tomography for scale-bridging, quantitative analysis of complex, hierarchical particle systems
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-18 20:00 EST
Alexander Götz, Fabian Lutter, Dennis Simon Possart, Daniel Augsburger, Usman Arslan, Sabrina Pechmann, Carmen Rubach, Moritz Buwen, Umair Sultan, Alexander Kichigin, Johannes Böhmer, Nora Vorlaufer, Peter Suter, Tor Hildebrand, Matthias Thommes, Peter Felfer, Nicolas Vogel, Katharina Breininger, Silke Christiansen, Benjamin Apeleo Zubiri, Erdmann Spiecker
This study presents a comprehensive workflow for investigating particulate materials through combined 360° electron tomography (ET), nano-computed X-ray tomography (nanoCT), and micro-computed X-ray tomography (microCT), alongside a versatile sample preparation routine. The workflow enables the investigation of size, morphology, and pore systems across multiple scales, from individual particles to large hierarchical structures. A customized tapered sample shape is fabricated using focused ion beam milling with the aim to optimize each imaging technique's field of view, facilitating high-resolution analysis of small volumes containing single particles, while also allowing for large-scale studies of thousands of particles for statistical relevance. By correlating data from same locations in different imaging modalities, the approach enhances the precision of quantitative analyses. The study highlights the importance of cross-scale, correlative three-dimensional microscopy for a comprehensive understanding of complex hierarchical materials. Precise data registration, segmentation using machine learning, and multimodal imaging techniques are crucial for unlocking insights into process-structure-property relationships and thus to optimize functional, hierarchical materials.
Materials Science (cond-mat.mtrl-sci)
Superconducting phase diagram of finite-layer nickelates Nd\(_{n+1}\)Ni\(_n\)O\(_{2n+2}\)
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-18 20:00 EST
Andreas Hausoel, Simone Di Cataldo, Motoharu Kitatani, Oleg Janson, Karsten Held
Following the successful prediction of the superconducting phase diagram for infinite-layer nickelates, here we calculate the superconducting \(T_{\mathrm{c}}\) vs. the number of layers \(n\) for finite-layer nickelates using the dynamical vertex approximation. To this end, we start with density functional theory, and include local correlations non-perturbatively by dynamical mean-field theory for \(n=2\) to 7. For all \(n\), the Ni \(d_{x^2-y^2}\) orbital crosses the Fermi level, but for \(n>4\) there are additional \((\pi, \pi)\) pockets or tubes that slightly enhance the layer-averaged hole doping of the \(d_{x^2-y^2}\) orbitals beyond the leading \(1/n\) contribution stemming from the valence electron count. We finally calculate \(T_{\mathrm{c}}\) for the single-orbital \(d_{x^2-y^2}\) Hubbard model by dynamical vertex approximation.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci), Superconductivity (cond-mat.supr-con)
7 pages + supplemental material
Observation of a zero-energy excitation mode in the open Dicke model
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-02-18 20:00 EST
Anton Bolian, Phatthamon Kongkhambut, Christoph Georges, Roy D. Jara Jr., José Vargas, Jens Klinder, Jayson G. Cosme, Hans Keßler, Andreas Hemmerich
Approaching phase boundaries in many-body systems can give rise to intriguing signatures in their excitation spectra. Here, we explore the excitation spectrum of a Bose-Einstein condensate strongly coupled to an optical cavity and pumped by an optical standing wave, which simulates the famous Dicke-Hepp-Lieb phase transition of the open Dicke model with dissipation arising due to photon leakage from the cavity. For weak dissipation, the excitation spectrum displays two strongly polaritonic modes. Close to the phase boundary, we observe an intriguing regime where the lower-energetic of these modes, instead of showing the expected roton-type mode softening, is found to approach and persist at zero energy, well before the critical pump strength for the Dicke-Hepp-Lieb transition boundary is reached. Hence, a peculiar situation arises, where an excitation is possible at zero energy cost, but nevertheless no instability of the system is created.
Quantum Gases (cond-mat.quant-gas)