CMP Journal 2025-01-30
Statistics
Nature: 1
Physical Review Letters: 4
Physical Review X: 1
arXiv: 54
Nature
HIV immune evasin Nef enhances allogeneic CAR T cell potency
Original Paper | Cancer immunotherapy | 2025-01-29 19:00 EST
Karlo Perica, Ivan Kotchetkov, Jorge Mansilla-Soto, Fiona Ehrich, Kevin Herrera, Yuzhe Shi, Anton Dobrin, Mithat Gönen, Michel Sadelain
Autologous chimeric antigen receptor (CAR) T cells are a genetically engineered therapy that is highly effective against B cell malignancies and multiple myeloma1. However, the length and cost of personalized manufacturing limits access and leaves patients vulnerable to disease progression. Allogeneic cell therapies have the potential to increase patient access and improve treatment outcomes but are limited by immune rejection2,3. To devise a strategy to protect allogeneic CAR T cells from host immune cells, we turned to lymphotropic viruses that have evolved integrated mechanisms for immune escape of virus-infected lymphocytes4. We find that viral evasins that partially reduce HLA class I expression can shelter CAR T cells from mismatched CD8+ T cells without triggering ‘missing-self' rejection by NK cells. However, this protection alone is insufficient to sustain effective allogeneic CAR T cell therapy. HIV-1 Nef uniquely also acts through the serine-threonine kinase Pak2 to abate activation-induced cell death and promote survival of CAR T cells in vivo. Thus, virus-like immune escape can harness multiple mechanisms that act in concert to enhance the therapeutic efficacy of allogeneic CAR T cells.
Cancer immunotherapy, Immune evasion, Translational immunology
Physical Review Letters
Probing Gluonic Saturation in Deeply Virtual Meson Production beyond Leading Power
Research article | Effective field theory | 2025-01-30 05:00 EST
Renaud Boussarie, Michael Fucilla, Lech Szymanowski, and Samuel Wallon
Exclusive diffractive meson production represents a golden channel for investigating gluonic saturation inside nucleons and nuclei. In this Letter, we settle a systematic framework to deal with beyond leading power corrections at small \(x\), including the saturation regime, and obtain the \({\gamma }^{\ast}\rightarrow M(\rho ,\phi ,\omega )\) impact factor with both incoming photon and outgoing meson carrying arbitrary polarizations. This is of particular interest since the saturation scale at modern colliders, although entering a perturbative regime, is not large enough to prevent higher-twist effects to be sizable.
Phys. Rev. Lett. 134, 041901 (2025)
Effective field theory, Hard scattering, Quantum chromodynamics, Quark matter
Quantum Offset of Velocity Imaging-Based Electron Spectrometry and the Electron Affinity of Arsenic
Research article | Electron beams & optics | 2025-01-30 05:00 EST
Christophe Blondel and Cyril Drag
Electron imaging has been routinely used for electron spectrometry. It has been ignored, however, that the maximum-intensity circles that surround electric field-produced electron spots do not materialize envelopes of trajectories, but the first interior fringes of a caustic. Neglecting the gap between the fringe and the parent envelope has resulted in spectrometric errors, notably on some reference values of electron affinities. Evidence for the effect is given by photodetachment microscopy of \({\mathrm{O}}^{- }\) and a measurement of the electron affinity of \(^{75}\mathrm{As}\), which is found to be 0.804 486(3) eV.
Phys. Rev. Lett. 134, 043001 (2025)
Electron beams & optics
Landau-Level Mixing and \(SU(4)\) Symmetry Breaking in Graphene
Research article | Landau levels | 2025-01-30 05:00 EST
Nemin Wei, Guopeng Xu, Inti Sodemann Villadiego, and Chunli Huang
Recent scanning tunneling microscopy experiments on graphene at charge neutrality under strong magnetic fields have uncovered a ground state characterized by Kekul'e distortion (KD). In contrast, nonlocal spin and charge transport experiments in double-encapsulated graphene, which has a higher dielectric constant, have identified an antiferromagnetic (AF) ground state. We propose a mechanism to reconcile these conflicting observations by showing that Landau-level mixing can drive a transition from AF to KD with the reduction of the dielectric screening. Our conclusion is drawn from studying the effect of Landau-level mixing on the lattice-scale, valley-dependent interactions to leading order in graphene's fine structure constant \(\kappa ={e}^{2}/(\hbar {v}_{F}\epsilon )\). This analysis provides three key insights: (1) valley-dependent interactions remain predominantly short-range with the \(m=0\) Haldane pseudopotential being at least an order of magnitude greater than the others, affirming the validity of delta-function approximation for these interactions. (2) The phase transition between the AF and KD states is driven by the microscopic process in the double-exchange Feynman diagram. (3) The magnitudes of the coupling constants are significantly boosted by remote Landau levels. Our model also provides a theoretical basis for numerical studies of fractional quantum Hall states in graphene.
Phys. Rev. Lett. 134, 046501 (2025)
Landau levels, Magnetic order, Quantum Hall effect, Graphene, Perturbation theory
Granular Temperature Controls Local Rheology of Vibrated Granular Flows
Research article | Granular flows | 2025-01-30 05:00 EST
Mitchell G. Irmer, Emily E. Brodsky, and Abram H. Clark
We use numerical simulations to demonstrate a local rheology for dense granular flows under shear and vibration. Granular temperature has been suggested as a rheological control but has been difficult to isolate. Here, we consider a granular assembly that is subjected to simple shear and harmonic vibration at the boundary, which provides a controlled source of granular temperature. We find that friction is reduced due to local velocity fluctuations of grains. All data obey a local rheology that relates the material friction coefficient, the granular temperature, and the dimensionless shear rate. We also observe that reduction in material friction due to granular temperature is associated with reduction in fabric anisotropy. We demonstrate that the temperature can be modeled by a heat equation with dissipation with appropriate boundary conditions, which provides complete closure of the system and allows a fully local continuum description of sheared, vibrated granular flows. This success suggests local rheology based on temperature combined with a diffusion equation for granular temperature may provide a general strategy to model dense granular flows.
Phys. Rev. Lett. 134, 048202 (2025)
Granular flows, Granular materials, Vibrofluidized granular materials
Physical Review X
Positive Oscillating Magnetoresistance in a van der Waals Antiferromagnetic Semiconductor
Research article | Antiferromagnetism | 2025-01-30 05:00 EST
Xiaohanwen Lin, Fan Wu, Nicolas Ubrig, Menghan Liao, Fengrui Yao, Ignacio Gutiérrez-Lezama, and Alberto F. Morpurgo
At low temperatures the resistance of a layered magnetic semiconductor shoots up and down in response to an increasing magnetic field.
Phys. Rev. X 15, 011017 (2025)
Antiferromagnetism, Magnetic order, Magnetism, Magnetoresistance, Magnetotransport, Phase diagrams, Transport phenomena, Layered semiconductors, Magnetic semiconductors
arXiv
Phonon-mediated electron attraction in SrTiO\(_3\) via the generalized Fr"ohlich and deformation potential mechanisms
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-30 20:00 EST
Norm M. Tubman, Christopher J.N. Coveney, Chih-En Hsu, Andres Montoya-Castillo, Marina R. Filip, Jeffrey B. Neaton, Zhenglu Li, Vojtech Vlcek, Antonios M. Alvertis
Superconductivity in doped SrTiO\(_3\) was discovered in 1964, the first superconducting transition observed in a doped semiconductor. However, the mechanism behind electron pairing in SrTiO\(_3\) remains a subject of debate. By developing a theoretical framework to incorporate dynamical lattice screening in the electronic Coulomb interactions of semiconductors and insulators, we demonstrate analytically that long-range electron-phonon interactions described by a generalized multi-phonon Fröhlich mechanism result in phonon-mediated electron-electron attraction in SrTiO\(_3\). Moreover, by combining our theory with first-principles calculations, we reveal an additional attractive interaction between electrons in SrTiO\(_3\) due to the deformation potential mechanism, arising from the mixed ionic-covalent character of the Ti-O bond. Our results may have implications for the emergence of phonon-mediated electron attraction and superconductivity in a broader range of materials.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Emergent multifractality in power-law decaying eigenstates
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-01-30 20:00 EST
Adway Kumar Das, Anandamohan Ghosh, Ivan M. Khaymovich
Eigenstate multifractality is of significant interest with potential applications in various fields of quantum physics. Most of the previous studies concentrated on fine-tuned quantum models to realize multifractality which is generally believed to be a critical phenomenon and fragile to random perturbations. In this work, we propose a set of generic principles based on the power-law decay of the eigenstates which allow us to distinguish a fractal phase from a genuine multifractal phase. We demonstrate the above principles in a 1d tight-binding model with inhomogeneous nearest-neighbor hopping that can be mapped to the standard quantum harmonic oscillator via energy-coordinate duality. We analytically calculate the fractal dimensions and the spectrum of fractal dimensions which are in agreement with numerical simulations.
Disordered Systems and Neural Networks (cond-mat.dis-nn), High Energy Physics - Theory (hep-th), Mathematical Physics (math-ph), Quantum Physics (quant-ph)
4.25 pages, 3 figures, 106 references + 3 pages in Appendices
A novel Gapless Quantum Spin Liquid in the S = 1 4d4-honeycomb material Cu3LiRu2O6
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-30 20:00 EST
Sanjay Bachhar, Nashra Pistawala, S. Kundu, Maneesha Barik, M. Baenitz, Jorg Sichelschmidt, Koji Yokoyama, P. Khuntia, Surjeet Singh, A.V. Mahajan
We report the discovery of a novel gapless quantum spin liquid in the S=1 honeycomb system Cu3LiRu2O6 with Ru4+ (4d4) where moments remain dynamic down to 50 mK. Heat capacity measurements show no sign of magnetic ordering down to 60 mK in spite of a Curie-Weiss temperature = -222 K indicating a strong antiferromagnetic interaction. In zero field, magnetic heat capacity shows a linear T-dependence with Sommerfeld coefficient = 107 mJ/mol K2 is much larger than that found in typical Fermi liquids. Our local probe 7Li nuclear magnetic resonance (NMR) measurements find a significant temperature-independent 7Li NMR shift (and hence a non-zero spin susceptibility) at low-T and a linear T-variation of the 7Li NMR spin-lattice relaxation rate 1/T1 at low-T reminiscent of fermionic excitations. Muon spin relaxation measurements detect neither long-range ordering nor spin freezing down to 50 mK and the temperature variation of the muon depolarization rate shows a gradual increase with decreasing temperature and a leveling off below about 1 K evincing a persistent spin dynamics common to several spin liquid candidates. Our results provide strong signatures of a quantum spin liquid in the titled honeycomb material.
Strongly Correlated Electrons (cond-mat.str-el)
5 pages and 6 figures in main, 8 pages and 16 figures in the supplement
Linear-time classical approximate optimization of cubic-lattice classical spin glasses
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-01-30 20:00 EST
Computing low-energy configurations (i.e., approximate optimization) of classical spin glasses is of relevance to both condensed matter and combinatorial optimization. Recent theoretical work opens the possibility to make its time complexity with quantum annealing generically polynomial, and D-Wave experiments can now achieve approximate optimization of cubic-lattice classical Ising spin glasses with $\(10^4\) spins. It is therefore timely to ask which short-range classical spin glasses are good candidates for demonstrating quantum advantage in the time complexity of approximate optimization. One intuition is to consider models with very rugged energy landscapes in configuration space, where optimization is extremely slow with state-of-the-art Monte-Carlo methods. However, here we provide evidence that short-range classical spin glasses may be approximately optimized in linear time and space with a very simple deterministic tensor-network heuristic regardless of ruggedness. On the cubic lattice with up to 50$\(50\)$50 spins, we obtain energy errors of $$3% for the \(\pm J\) model used in recent D-Wave experiments, and $$5% for much harder planted-solution instances, all in less than one hour per instance. For cubic-lattice-Ising reductions of unweighted Max-Cut on random 3-regular graphs with up to 300 vertices, we find energy errors of $<$1% and approximation ratios of about 72-88%. These results inform the search for quantum advantage and suggest an efficient classical method for generating warm starts for other spin-glass optimization algorithms. Our algorithm is amenable to massive parallelization and may also allow for low-power, accelerated implementations with photonic matrix-multiplication hardware.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Quantum Physics (quant-ph)
9 pages, 10 figures
On the first positive position of a random walker
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-30 20:00 EST
Claude Godrèche, Jean-Marc Luck
The distribution of the first positive position reached by a random walker starting from the origin is fundamental for understanding the statistics of extremes and records in one-dimensional random walks. We present a comprehensive study of this distribution, focusing particularly on its moments and asymptotic tail behaviour, in the case where the step distribution is continuous and symmetric, encompassing both diffusive random walks and Lévy flights.
Statistical Mechanics (cond-mat.stat-mech), Probability (math.PR)
61 pages, 14 figures
Engineering Point Defects in MoS2 for Tailored Material Properties using Large Language Models
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-30 20:00 EST
Abdalaziz Al-Maeeni, Denis Derkach, Andrey Ustyuzhanin
The tunability of physical properties in transition metal dichalcogenides (TMDCs) through point defect engineering offers significant potential for the development of next-generation optoelectronic and high-tech applications. Building upon prior work on machine learning-driven material design, this study focuses on the systematic introduction and manipulation of point defects in MoS2 to tailor their properties. Leveraging a comprehensive dataset generated via density functional theory (DFT) calculations, we explore the effects of various defect types and concentrations on the mate rial characteristics of TMDCs. Our methodology integrates the use of pre-trained large language models to generate defect configurations, enabling efficient predictions of defect-induced property modifications. This research differs from traditional methods of material generation and discovery by utilizing the latest advances in transformer model architecture, which have proven to be efficient and accurate discrete predictors. In contrast to high-throughput methods where configurations are generated randomly and then screened based on their physical properties, our approach not only enhances the understanding of defect-property relationships in TMDCs but also provides a robust framework for designing materials with bespoke properties. This facilitates the advancement of materials science and technology.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
Nonequilibrium Green's Function Formalism Applicable to Discrete Impurities in Semiconductor Nanostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-30 20:00 EST
A new theoretical framework for the nonequilibrium Green's function (NEGF) scheme is presented to account for the discrete nature of impurities doped in semiconductor nanostructures. The short-range part of impurity potential is included as scattering potential in the self-energy due to spatially localized impurity scattering, and the long-range part of impurity potential is treated as the self-consistent Hartree potential by coupling with the Poisson equation. The position-dependent impurity scattering rate under inhomogeneous impurity profiles is systematically derived so that its physical meaning is clarified. The position dependence of the scattering rate turns out to be represented by the `center of mass' coordinates in the Wigner coordinates, rather than the real-space coordinates. Consequently, impurity scattering is intrinsically nonlocal in space. The proposed framework is applied to cylindrical thin wires under the quasi-one-dimensional (quasi-1D) approximation. We show explicitly how the discrete nature of impurities affects the transport properties such as electrostatic potential, local density of states, carrier density, scattering rates, and mobility.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Phase transition in quasi-flat band superconductors
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-30 20:00 EST
We investigate superconductivity in a two-dimensional material described by a two-band heavy-fermion model, where hybridization between a dispersive band and a flat band introduces a quasi-flat dispersion to the otherwise localized flat-band electrons. The enhanced density of states in the quasi-flat band raises the crossover temperature for an inhomogeneous preformed Cooper pair state. The superconducting phase stiffness and the Berezinskii-Kosterlitz-Thouless (BKT) temperature are governed by the Fermi surface contribution induced by hybridization. We compute the crossover and BKT temperatures, revealing a dome-like dependence on doping. When the pairing amplitude exceeds the energy width of the quasi-flat band, superconductivity is suppressed, and the inhomogeneous pairing regime expands linearly with increasing interaction strength. However, in the opposite case, the BKT temperature reaches a maximum value that is only numerically less than the energy width of the quasi-flat band. We also discuss our results in the context of superconductivity in graphene-based systems.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
13 pages, 3 figures
L'evy noise effects on Josephson junctions
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-30 20:00 EST
We review three different approaches to investigate the non-equilibrium stochastic dynamics of a Josephson junction affected by Lévy-distributed current fluctuations. First, we study the lifetime in the metastable superconducting state of current-biased short and long junctions, in the presence of Gaussian and Lévy noise sources. We highlight the noise-induced nonmonotonic behavior of the mean switching time as a function of noise intensity and driving frequency, that is the noise enhanced stability and the stochastic resonant activation, respectively. Then, we characterize the Lévy noise source through the average voltage drop across a current-biased junction. The voltage measurement versus the noise intensity allows to infer the value of the stability index that characterizes Lévy-distributed fluctuations. The numerical calculation of the average voltage drop across the junction well agrees with the analytical estimate of the average velocity for Lévy-driven escape processes from a metastable state. Finally, we look at the distribution of switching currents out of the zero-voltage state, when a Lévy noise signal is added to a linearly ramped bias current. The analysis of the cumulative distribution function of the switching currents gives information on both the Lévy stability index and the intensity of fluctuations. We present also a theoretical model to catch the features of the Lévy signal from a measured distribution of switching currents. The phenomena discussed in this work can pave the way for an effective and reliable Josephson-based scheme to characterize Lévy components eventually embedded in an unknown noisy signal.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
20 pages, 9 figures
Chaos, Solitons Fractals, 153, 111531 (2021)
Two-dimensional talc as a natural hyperbolic material
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-30 20:00 EST
Flávio H. Feresa, Francisco C. B. Maia, Shu Chen, Rafael A. Mayer, Maximillian Obst, Osama Hatem, Lukas Wehmeier, Tobias Nörenberg, Matheus S. Queiroz, Victor Mazzotti, J. Michael Klopf, Susanne C. Kehr, Lukas M. Eng, Alisson R. Cadore, Rainer Hillenbrand, Raul O. Freitas, Ingrid D. Barcelos
This study demonstrates that two-dimensional talc, a naturally abundant mineral, supports hyperbolic phonon-polaritons (HPhPs) at mid-infrared wavelengths, thus offering a low-cost alternative to synthetic polaritonic materials. Using scattering scanning near-field optical microscopy (s-SNOM) and synchrotron infrared nano spectroscopy (SINS), we reveal tunable HPhP modes in talc flakes of a long lifetime. These results highlight the potential of natural 2D talc crystals to constituting an effective platform for establishing scalable optoelectronic and photonic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
8 pages, 4 figures
Role of interface mixing on coherent heat conduction in periodic and aperiodic superlattices
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-30 20:00 EST
Theodore Maranets, Evan Doe, Yan Wang
Superlattices (SLs) can induce phonon coherence through the periodic layering of two or more materials, enabling tailored thermal transport properties. While most theoretical studies assume atomically sharp, perfect interfaces, real SLs often feature atomic interdiffusion spanning approximately a single atomic layer or more. Such interface mixing can significantly influence phonon coherence and transport behavior. In this study, we employ atomistic wave-packet simulations to systematically investigate the effects of interface mixing on coherent heat conduction. Our analysis identifies two competing mechanisms that govern phonon transport across mixed interfaces: (1) Interface mixing disrupts coherent mode-conversion effects arising from the interface arrangement. (2) The disorder enhances the potential for interference events, generating additional coherent phonon transport pathways. The second mechanism enhances the transmission of Bragg-reflected modes in periodic SLs and most phonons in aperiodic SLs, which otherwise lack coherent mode-conversion in perfect structures. Conversely, the first mechanism dominates in periodic SLs for non-Bragg-reflected modes, where transmission is already high due to substantial mode-conversion. These findings provide insights into the interplay between interface imperfections and phonon coherence.
Materials Science (cond-mat.mtrl-sci)
Singularity and universality from von Neumann to R'enyi entanglement entropy and disorder operator in Motzkin chains
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-30 20:00 EST
Jianyu Wang, Zenan Liu, Zheng Yan, Congjun Wu
The Rényi entanglement entropy is widely used in studying quantum entanglement properties in strongly correlated systems, whose analytic continuation as \(n \to 1\) is often believed to give rise to the celebrated von Neumann entanglement entropy. However, this process for the colored Motzkin spin chain exhibits a singularity that yields different scaling behaviors of \(\sim \sqrt{l}\) and \(\sim \log{l}\) for the von Neumann and Rényi entropies, respectively. It can be understood by the exponential increasing desity of states in its entanglement spectrum. We have also employed disorder operators under various symmetries to study such a system. The analytical and numerical results reveal that the scaling of disorder operators is also \(\log{l}\) in the leading term, the same as the Rényi entanglement entropy. We propose that the coefficient of the term \(\log{l}\) \(l\) is a universal constant, both in Rényi entropies and disorder operators, which could be used to identify the constraint physics of Motzkin walks.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
Anomalous proximity effect of a spin-singlet superconductor with a spin-orbit interaction
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-30 20:00 EST
Jaechul Lee, Satoshi Ikegaya, Yasuhiro Asano
The anomalous proximity effect of a spin-triplet p-wave superconductor has been known as a part of the Majorana physics. We demonstrate that a spin-singlet d-wave superconductor exhibits the anomalous proximity effect in the presence of a specific spin-orbit interaction. The results show the quantization of the zero-bias conductance in a dirty normal-metal/superconductor junction. We also discuss a relation between our findings and results in an experiment on a CoSi_2/TiSi_2 junction.
Superconductivity (cond-mat.supr-con)
8 pages, 6 figures
Photo-induced spall failure of (111) twist grain boundaries in Ni bicrystals
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-30 20:00 EST
Spall failure, a complex failure mechanism driven by tensile stress wave interactions, has been extensively studied in single-crystal FCC metals, revealing a precursor stage involving dislocation emission along closed-packed directions. Here we investigate the photo-induced spall failure of Ni bicrystals under a two-pulse laser configuration, exploring various misorientation angles through two-temperature molecular dynamics (MD) simulations including electronic effects to simulate light-matter interaction. Our findings demonstrate that light-matter interactions can induce spall failure at the sample center, similar to conventional plate-impact methods, when two laser-pulses are applied to the front and back surfaces of the sample. The study reveals the significant influence of misorientation angles on dislocation activity and spall behavior, where grain boundaries (GBs) play pivotal roles, either promoting or impeding dislocation interactions. Furthermore, our work highlights the potential for enhancing spall resistance by tailoring materials through misorientation angle variation.
Materials Science (cond-mat.mtrl-sci)
Quantitative Modeling of Point Defects in \(\beta\)-Ga2O3 Combining Hybrid Functional Energetics with Semiconductor and Processes Thermodynamics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-30 20:00 EST
Khandakar Aaditta Arnab, Megan Stephens, Isaac Maxfield, Channyung Lee, Elif Ertekin, Ymir K. Frodason, Joel B. Varley, Michael A. Scarpulla
B-gallium oxide (B-Ga2O3) is of high interest for power electronics because of its unique combination of melt growth, epitaxial growth, n-type dopability, ultrawide bandgap, and high critical field. Optimization of crystal growth processes to promote beneficial defects and suppress harmful ones requires accurate quantitative modelling of both native and impurity defects. Here we quantitatively model defect concentrations as a function of bulk crystal growth conditions and demonstrate the necessity of including effects such as bandgap temperature dependence, chemical potentials from thermochemistry, and defect vibrational entropy in modelling based on defect formation energies computed by density functional theory (DFT) with hybrid functionals. Without these contributions, grossly-erroneous and misleading predictions arise, e.g. that n-type doping attempts would be fully compensated by Ga vacancies. Including these effects reproduces the experimental facts that melt-grown Sn-doped B-Ga2O3 crystals are conductive with small compensation while annealing the same crystals in O2 at intermediate temperatures renders them insulating. To accomplish this modeling, we developed a comprehensive modelling framework (KROGER) based on calculated defect formation energies and flexible thermodynamic conditions. These capabilities allow KROGER to capture full and partial defect equilibria amongst native defects and impurities occurring during specific semiconductor growth or fabrication processes. We use KROGER to model 873 charge-states of 259 defects involving 19 elements in conditions representing bulk crystal growth by edge-fed growth (EFG) and annealing in O2. Our methodology is transferrable to a wide range of materials beyond B-Ga2O3. Integration of thermodynamic and first-principles modelling of point defects provides insight into optimization of point defect populations in growth and processing.
Materials Science (cond-mat.mtrl-sci)
39 pages, 6 figures, references
Describing Self-organized Criticality as a continuous phase transition
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-30 20:00 EST
Can the concept of self-organized criticality, exemplified by models such as the sandpile model, be described within the framework of continuous phase transitions? In this paper, we provide extensive numerical evidence supporting an affirmative answer. Specifically, we explore the BTW and Manna sandpile models as instances of percolation transitions from disordered to ordered phases. To facilitate this analysis, we introduce the concept of drop density, a continuously adjustable control variable that quantifies the average number of particles added to a site. By tuning this variable, we observe a transition in the sandpile from a sub-critical to a critical phase. Additionally, we define the scaled size of the largest avalanche occurring from the beginning of the sandpile as the order parameter for the self-organized critical transition and analyze its scaling behavior. Furthermore, we calculate the correlation length exponent and note its divergence as the critical point is approached. The finite size scaling analysis of the avalanche size distribution works quite well at the critical point of the BTW sandpile.
Statistical Mechanics (cond-mat.stat-mech)
11 pages, 13 figures
Chiral Altermagnon in MnTe
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-30 20:00 EST
Daniel Jost, Resham B. Regmi, Samuel Sahel-Schackis, Monika Scheufele, Marcel Neuhaus, Rachel Nickel, Flora Yakhou, Kurt Kummer, Nicholas Brookes, Lingjia Shen, Georgi L. Dakovski, Nirmal J. Ghimire, Stephan Geprägs, Matthias F. Kling
Altermagnetism has surfaced as a novel magnetic phase, bridging the properties of ferro- and anti-ferromagnetism. The momentum-dependent spin-splitting observed in these materials reflects their unique symmetry characteristics which also establish the conditions for chiral magnons to emerge. Here we provide the first direct experimental evidence for a chiral magnon in the altermagnetic candidate MnTe, revealed by circular-dichroism resonant inelastic X-ray scattering (CD-RIXS). This mode which we term chiral altermagnon exhibits a distinct momentum dependence consistent with the proposed altermagnetic \(g-\)wave symmetry of MnTe. Our results reveal a new class of magnetic excitations, demonstrating how altermagnetic order shapes spin dynamics and paves the way for advances in spintronic and quantum technologies.
Materials Science (cond-mat.mtrl-sci)
Effect of metal (Ti) interlayer on fracture toughness of TiN thin films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-30 20:00 EST
Nidhin George Mathews, Aloshious Lambai, Marcus Hans, Jochen M. Schneider, Gaurav Mohanty, Balila Nagamani Jaya
Titanium Nitride (TiN) is widely used as a protective coating due to its high hardness, but suffers from inherent brittleness and low fracture toughness, limiting its applicability. The layering of Titanium Nitride films with metallic Titanium (Ti) improves the overall fracture behavior of system by modifying the crack driving force due to elastic-plastic mismatch between the layers. Microcantilever fracture tests were carried out on bilayer (Ti-TiN, TiN-Ti) and trilayer (Ti-TiN-Ti) systems to determine the fracture toughness and study the fundamental crack growth behavior. The initiation fracture toughness in bilayer system with crack in Ti layer is almost 70% higher when compared to crack in TiN layer. In Ti-TiN bilayer the crack propagated catastrophically post linear elastic deformation, whereas the crack was arrested at the TiN/Ti interface in both TiN-Ti and Ti-TiN-Ti systems due to plastic energy dissipation in the Ti layer. Incorpration of crack tip plasticity due to the metallic layer increased the total resistance to fracture by around eight times compared to the Ti-TiN bilayer.
Materials Science (cond-mat.mtrl-sci)
14 pages, 5 figures
Spin-forbidden excitations in the magneto-optical spectra of CrI\(_3\) tuned by covalency
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-30 20:00 EST
Connor A. Occhialini, Luca Nessi, Luiz G. P. Martins, Ahmet Kemal Demir, Qian Song, Vicky Hasse, Chandra Shekhar, Claudia Felser, Kenji Watanabe, Takashi Taniguchi, Valentina Bisogni, Jonathan Pelliciari, Riccardo Comin
Spin-forbidden (\(\Delta S \neq 0\)) multiplet excitations and their coupling to magnetic properties are of increasing importance for magneto-optical studies of correlated materials. Nonetheless, the mechanisms for optically brightening these transitions and their generality remain poorly understood. Here, we report magnetic circular dichroism (MCD) spectroscopy on the van der Waals (vdW) ferromagnet (FM) CrI\(_3\). Previously unreported spin-forbidden (\(\Delta S = 1\)) \({}^4A_{2\mathrm{g}} \to{}^2E_\mathrm{g}/{}^2T_{1\mathrm{g}}\) Cr\({}^{3+}\) \(dd\) excitations are observed near the ligand-to-metal charge transfer (LMCT) excitation threshold. The assignment of these excitations and their Cr\(^{3+}\) multiplet character is established through complementary Cr \(L_3\)-edge resonant inelastic X-ray scattering (RIXS) measurements along with charge transfer multiplet (CTM) calculations and chemical trends in the chromium trihalide series (CrX\(_3\), X = Cl, Br, I). We utilize the high sensitivity of MCD spectroscopy to study the thickness dependent optical response. The spin-forbidden excitations remain robust down to the monolayer limit and exhibit a significant magnetic field tunability across the antiferromagnetic to FM transition in few-layer samples. This behavior is associated to changes in the metal-ligand covalency with magnetic state, as supported by our CTM analysis. Our results clarify the magneto-optical response of CrI\(_3\) and identify covalency as a central mechanism for the brightening and field-tunability of spin-forbidden multiplet excitations.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Diagonal superexchange in a simple square CuO\(_2\) lattice
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-30 20:00 EST
V. A. Gavrichkov, S. I. Polukeev, S. G. Ovchinnikov
Many microscopic models with interaction between the next-nearest neighbours as a key parameter to cuprate physics inspired us to study here the diagonal superexchange interaction in the CuO\(_2\) layer. Our investigation shows the models with extended hopping give a correct representation of magnetic interactions only in a hypothetical square CuO\(_2\) layer, where the diagonal superexchange interaction with the next-nearest neighbours neighbors always has the AFM nature. The conclusions are based on the presence of a symmetry prohibition on the FM contribution to the total diagonal superexchange between the next-nearest neighbors for a simple square CuO\(_2\) layer, but not for the real CuO\(_2\) layer. We actually confirm also there are justified reasons to consider magnetic frustrations and high sensitivity of spin nanoinhomogeneity to a breaking square symmetry.
Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 4 figures
Enhancement of superconductivity on thin film of Sn under high pressure
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-30 20:00 EST
Misaki Sasaki, Masahiro Ohkuma, Ryo Matsumoto, Toru Shinmei, Tetsuo Irifune, Yoshihiko Takano, Katsuya Shimizu
We investigated the pressure effects of a superconductivity on thin films of Sn. Elemental superconductor Sn with a body-centered tetragonal structure, \(\beta\)-Sn, exhibits superconductivity below the superconducting transition temperature (\(T_{\rm c}=3.72\) K) at ambient pressure. \(T_{\rm c}\) of Sn increases with lowering dimension such as in thin film and nanowire growth, or by high-pressure application. For thin films, \(T_{\rm c}\) exhibits a slight increase up to approximately 4 K compared to the bulk value, attributable to the crystalline size and lattice disorder. By applying pressure on a bulk Sn, \(T_{\rm c}\) decreases with increasing pressure from 3.72 K to 5.3 K with the structural transformation into \(\gamma\)-Sn around 10 GPa. However, the combination of these effects on thin films of Sn, namely, thin-film growth and pressure effects, remains underexplored. In this study, we combined film-growth and pressure-application techniques to further increase \(T_{\rm c}\) using a diamond anvil cell with boron-doped diamond electrodes. The drop of the electrical resistance suggesting the onset of \(T_{\rm c}\) on the thin film reached above 6 K in \(\gamma\)-Sn phase. Further, the upper critical magnetic field was drastically enhanced. Atomic force microscopy suggests that the refinement of the grain size of the thin film under the non-hydrostatic pressure conditions contributes to stabilizing the higher \(T_{\rm c}\) of \(\gamma\)-Sn.
Superconductivity (cond-mat.supr-con)
Magnetic metastability driven Anomalous Hall Effect in Fe\(_{x}\)TaS\(_2\)
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-30 20:00 EST
Mohamad Numan, Prasanta Chowdhury, Sanat Adhikary, Saurav Giri, Jhuma Sannigrahi, Matthias Gutmann, Souvik Chatterjee, Subham Majumdar
We have investigated the magnetic and transport properties of Fe-intercalated TaS\(2\) single crystals. The material exhibits ferromagnetic order with very high anisotropy, with the \(c\)-axis as the easy axis. The magnetic moments of the compound become arrested during field cooling in magnetic fields above 500 Oe. As a result, it retains thermoremanent magnetization (TRM) up to the transition temperature (\(T_C\)). Fe\(_{x}\)TaS\(_2\) displays a large anomalous Hall effect (AHE) with a pronounced hysteresis loop, similar to the isothermal magnetization. Our key observation suggests that the presence of TRM breaks the time-reversal symmetry below \(T_C\), producing an AHE in zero applied field with the same value as that obtained from typical field variation. Scaling analysis indicates that skew scattering is the primary mechanism for the observed AHE.
Strongly Correlated Electrons (cond-mat.str-el)
8 pages, 8 figures
Third-order rectification in centrosymmetric metals
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-30 20:00 EST
Rectification, the conversion of AC fields into DC currents, is crucial for optoelectronic applications such as energy harvesting and wireless communication. However, it is conventionally absent in centrosymmetric systems due to vanishing second-order optical responses. Here, we demonstrate significant rectification and photogalvanic currents in centrosymmetric metals via third-order nonlinear optical responses, driven by finite Fermi surface and disorder-induced contributions. We unveil distinct band geometric mechanisms -- including Berry curvature quadrupole, Fermi surface injection, and shift effects -- and classify all symmetry-allowed rectification responses. Using graphene as an example, we illustrate rectification tunability via light polarization and helicity, enabling rectification engineering in centrosymmetric materials for energy-efficient photodetection and terahertz applications.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
8 pages, 3 figures
Direct Observation of Vortices and Antivortices Generation in Phase-Separated Superconductor Sn-Pb Solder
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-30 20:00 EST
Hiroto Arima, Takumi Murakami, Yuto Kinoshita, Hossein Sepehri-Amin, Masashi Tokunaga, Tsutomu Nojima, Yoshikazu Mizuguchi
Quantized vortices in type-II superconductors provide insights into the mechanisms of superconductivity. However, the generation of antivortices, characterized by magnetization antiparallel to the external magnetic field, remains less understood. In this study, we investigate Sn-Pb solder, a superconductor with phase-separated Sn and Pb phases, and report the observation of both vortices and antivortices. Scanning SQUID (superconducting quantum interference device) microscopy revealed the presence of both vortices and antivortices, while magneto-optical imaging demonstrated flux avalanches. Our results demonstrate that Sn in Sn-Pb solder behaves as a type-II superconductor when magnetic fluxes are trapped, despite bulk Sn being a type-I superconductor with a transition temperature (TcSn) of 3.7 K. Our findings suggest that the size effect and proximity effect with Pb contribute synergistically to induce type-II superconductivity in Sn Notably, vortices were observed at temperatures as high as 5 K, exceeding the bulk TcSn. Furthermore, the interplay between the type-I superconducting Pb phase and the type-II superconducting Sn phase results in the generation of antivortices, providing a mechanism to accommodate excess magnetic flux. This study shed light on new research on composites combining type-I and type-II superconductors.
Superconductivity (cond-mat.supr-con)
27 pages, 15 figures
Bacterial dimensions sensitively regulate surface diffusivity and residence time
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-30 20:00 EST
Premkumar Leishangthem, Xuan Wang, Junan Chen, Shengqi Yang, Xinliang Xu
Run-and-tumble is a common but vital strategy that bacteria employ to explore environment suffused with boundaries, as well as to escape from entrapment. In this study we reveal how this strategy and the resulting dynamical behavior can be sensitively regulated by bacterial dimensions. Our results demonstrate that the logarithm of the surface residence time for bacteria with constant tumble bias is linearly related to a dimensionless parameter of bacterial intrinsic size characteristics, where a small variation in bacterial dimensions, which is natural in a suspension, reproduces well the experimentally observed large variation in bacterial residence time. Furthermore, our results predict that the optimal tumble bias corresponding to the maximum surface diffusivity depends strongly on bacterial dimensions, where the same small variation in bacterial dimensions gives rise to a strongly diversified optimal tumble bias and an order of magnitude change in surface diffusivity.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech), Biological Physics (physics.bio-ph)
5 pages, 4 figures
Electron trapping via magnetic and laser fields in gapped graphene quantum dots
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-30 20:00 EST
Ahmed Bouhlal, Mohammed El Azar, Aotmane En Naciri, Elmustapha Feddi, Ahmed Jellal
We study electron scattering in graphene quantum dots (GQDs) under the combined influence of a magnetic field, an energy gap, and circularly polarized laser irradiation. Using the Floquet approach and the Dirac equation, we derive the energy spectrum solutions. The scattering coefficients are calculated explicitly by matching the eigenspinors at the GQD interfaces, revealing a dependence on several physical parameters. In addition, we compute the scattering efficiency, the electron density distribution, and the lifetime of the quasi-bound states. Our numerical results show that the presence of an energy gap and circularly polarized laser irradiation enhances the localization of the electron density within the GQDs, leading to an increase in the lifetime of the quasi-bound states. In particular, the intensity and polarization of the light influence the scattering process, allowing the manipulation of the electron confinement state. These results highlight the importance of combining magnetic fields and polarized light to control electronic transport in graphene nanostructures.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
12 pages, 9 figures
Quasi-two-dimensional Fermi surfaces of the antiferromagnet U\(_2\)RhIn\(_8\) revealed by de Haas-van Alphen measurements
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-30 20:00 EST
D. Aoki, Y. Homma, H. Harima, I. Sheikin
We report temperature-dependent Hall effect and low-temperature de Haas-van Alphen (dHvA) effect measurements of the antiferromagnetic heavy-fermion compound U\(_2\)RhIn\(_8\). Temperature dependence of the Hall resistivity suggests a considerable reduction of the carrier density in the antiferromagnetic phase. The observed angular dependence of the dHvA frequencies suggests the existence of three almost ideally two-dimensional Fermi surfaces one of which is quite large. The measured effective masses range from 2\(m_0\) to 14\(m_0\) for the field applied along the \(c\) axis. Local density approximation band-structure calculations performed for the paramagnetic ground state reveal more three-dimensional Fermi surfaces than those observed in the experiment. On the other hand, Fermi surfaces obtained for the antiferromagnetic ground state by band folding are more two dimensional. These calculations account reasonably well for the experimental results assuming a slight modification of the calculated Fermi surfaces.
Strongly Correlated Electrons (cond-mat.str-el)
10 pages, 9 figures, accepted for publication in Phys. Rev. B
Selective Fabrication of Monolayer 1H- and 1T'-WTe2
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-30 20:00 EST
Ryuichi Ando, Katsuaki Sugawara, Tappei Kawakami, Takashi Takahashi, Takafumi Sato
We selectively fabricated monolayers of octahedral (1H) and distorted trigonal (1T') WTe2 on graphene/SiC(0001) by controlling the substrate temperature during epitaxy. Angle-resolved photoemission spectroscopy, combined with first-principles band-structure calculations, has revealed several drastic differences between these two polymorphs. The 1T' phase exhibits a semiconducting character with a nearly-zero energy gap, while the 1H phase shows a large band gap and the band splitting at the K/K' point. The present results pave a pathway toward developing nanoelectronic devices based with WTe2.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
J. Phys. Soc. Jpn. 93, 085002 (2024)
Unusual temperature dependence of the band structure associated with local atomic distortion in monolayer 1T'-WTe2
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-30 20:00 EST
Ryuichi Ando, Katsuaki Sugawara, Tappei Kawakami, Koki Yanagizawa, Ken Yaegashi, Takashi Takahashi, Takafumi Sato
The ground state of monolayer 1T'-WTe2 has been a target of intensive debate on whether or not it is a two-dimensional topological insulator (2D TI) associated with exciton formation. We investigated the band structure of an epitaxial monolayer 1T'-WTe2 film grown on graphene/SiC(0001) in a wide temperature range of T = 40 - 400 K by angle-resolved photoemission spectroscopy (ARPES). We observed an electron band above the Fermi level (EF) slightly away from the {} point, together with four hole bands below EF just at the {} point. This signifies an indirect band gap exceeding 0.1 eV in support of the 2D-TI phase with the inverted band structure. We uncovered an unexpectedly large downward shift of valence bands upon cooling, accompanied with an upward shift of the conduction band. Comparison of the ARPES-derived band structure with first-principles band calculations suggests that the observed band shift is ascribed to the systematic local atomic distortion of tungsten atoms, which should be incorporated into the interpretation of unusual transport properties of 1T'-WTe2.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Phys. Rev. Materials 9, L011001 (2025)
Quantifying the amplitudes of ultrafast magnetization fluctuations in Sm\(_{0.7}\)Er\(_{0.3}\)FeO\(_{3}\) using femtosecond noise correlation spectroscopy
New Submission | Other Condensed Matter (cond-mat.other) | 2025-01-30 20:00 EST
M. A. Weiss, F. S. Herbst, G. Skobjin, S. Eggert, M. Nakajima, D. Reustlen, A. Leitenstorfer, S. T. B. Goennenwein, T. Kurihara
Spin fluctuations are an important issue for the design and operation of future spintronic devices. Femtosecond noise correlation spectroscopy (FemNoC) was recently applied to detect ultrafast magnetization fluctuations. FemNoC gives direct access to the spontaneous fluctuations of the magnetization in magnetically ordered materials. In FemNoC experiments, the magnetic fluctuations are imprinted on the polarization state of two independent femtosecond probe pulses upon transmission through a magnetic sample. Using a subharmonic demodulation scheme, the cross-correlation of the signals from both pulse trains is calculated. Here, we quantitatively link the FemNoC output signal to an optical polarization rotation, and then in turn to the magnitude of the inherent spin fluctuations. To this end, three different calibration protocols are presented and compared in accuracy. Ultimately, we quantitatively determine both the variance of optical polarization noise in rad\(^2\), and that of the ultrafast magnetization fluctuations in (A/m)\(^2\).
Other Condensed Matter (cond-mat.other), Optics (physics.optics)
Mechanism of Oleic Acid-Mediated Sulfur Vacancy Healing in monolayer WS\(_2\)
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-30 20:00 EST
Leon Daniel, Dedi Sutarma, Osamah Kharsah, Charleen Lintz, Peter Kratzer, Marika Schleberger
We uncover the mechanism behind the enhancement of photoluminescence yield in monolayer WS\(_2\) through oleic acid treatment, a promising scalable strategy for defect healing. By inducing sulfur vacancies through thermal treatment and monitoring the changes in photoluminescence yield and emission spectra, we demonstrate that oleic acid heals the sulfur vacancy by providing substitutional oxygen. Using density functional theory calculations, we provide insight into the underlying mechanism governing the oleic acid-mediated sulfur vacancy healing process. Our findings suggest that effective defect passivation by oxygen doping can be achieved through chemical treatment, opening a pathway for oxygen doping in transition metal dichalcogenides. However, we also highlight the limitations of chemical treatment, which may only lead to small increases in photoluminescence yield beyond a certain point.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
22 pages, 5 figures
Magnetic Phase Diagram of YbRh\(_{2}\)Si\(_{2}\): the Influence of Hyperfine Interactions
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-30 20:00 EST
Jan Knapp, Lev V. Levitin, Jan Nyeki, Brian Cowan, John Saunders, Manuel Brando, Christoph Geibel, Kristin Kliemt, Cornelius Krellner
We report the determination of the magnetic phase diagram of the heavy fermion metal YbRhSi in magnetic fields up to 70,mT applied perpendicular to the crystallographic c-axis. By a combination of heat capacity, magneto-caloric, and magneto-resistance measurements we map two antiferromagnetic phases: the electronic AFM1 below 70,mK and electro-nuclear AFM2 below 1.5,mK. The measurements extend into the microkelvin regime to explore the quantum phase transitions in this system. We demonstrate how the hyperfine interaction significantly modifies the phase diagram and the putative field-tuned quantum critical point. The determination of the rich magnetic properties of YbRhSi is essential to understanding the interplay of the two magnetic orders and superconductivity in this compound.
Strongly Correlated Electrons (cond-mat.str-el)
Anomalous Raman scattering in layered AgCrP\(_2\)Se\(_6\): Helical modes and excitation energy-dependent intensities
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-30 20:00 EST
Rahul Rao, Jie Jiang, Ruth Pachter, Thuc T. Mai, Valentine Mohaugen, Maria F. Muñoz, Ryan Siebenaller, Emmanuel Rowe, Ryan Selhorst, Andrea N. Giordano, Angela R. Hight Walker, Michael A. Susner
Structural anisotropy in layered two-dimensional materials can lead to highly anisotropic optical absorption which, in turn, can profoundly a^ect their phonon modes. These e^ects include lattice orientation-dependent and excitation energy-dependent mode intensities that can enable new phononic and optoelectronic applications. Here, we report anomalous Raman spectra in single-crystalline AgCrP\(_2\)Se\(_6\), a layered antiferromagnetic material. Density functional theory calculations and experimental measurements reveal several unique features in the Raman spectra of bulk and exfoliated AgCrP\(_2\)Se\(_6\) crystals including three helical vibrational modes. These modes exhibit large Raman optical activities (circular intensity di^erences) in bulk AgCrP\(_2\)Se\(_6\), which progressively decrease with thickness. We also observe strong excitation energy dependent peak intensities as well as a decrease in anti-Stokes peak intensities at room temperature with increasing excitation energy, resulting in an apparent cooling by up to 220 K. All of these anomalies in bulk and exfoliated flakes are attributed to the unique ABC layer stacking structure of AgCrP\(_2\)Se\(_6\) and to the smaller unit cell volume that causes hybridization between the Se and Ag/Cr electron densities, resulting in charge transfer and strongly a^ecting the electron-phonon coupling. This work thus positions AgCrP\(_2\)Se\(_6\) as an exciting new 2D material for optical and phononic applications.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Optics (physics.optics)
22 pages, 6 figures
Microscopic Observation of Non-Ergodic States in Two-Dimensional Non-Topological Bubble Lattices
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-30 20:00 EST
S. Pylypenko, M. Winter, U. K. Rößler, D. Pohl, R. Kyrychenko, M. C. Rahn, B. Achinuq, J. R. Bollard, P. Vir, G. van der Laan, T. Hesjedal, J. Schultz, B. Rellinghaus, C. Felser, A. Lubk
Disordered 2D lattices, including hexatic and various glassy states, are observed in a wide range of 2D systems including colloidal nanoparticle assemblies and fluxon lattices. Their disordered nature determines the stability and mobility of these systems, as well as their response to the external stimuli. Here we report on the controlled creation and characterization of a disordered 2D lattice of non-topological magnetic bubbles in the non-centrosymmetric ferrimagnetic alloy Mn\(_{1.4}\)PtSn. By analyzing the type and frequency of fundamental lattice defects, such as dislocations, the orientational correlation, as well as the induced motion of the lattice in an external field, a non-ergodic glassy state, stabilized by directional application of an external field, is revealed.
Materials Science (cond-mat.mtrl-sci), Disordered Systems and Neural Networks (cond-mat.dis-nn), Computational Physics (physics.comp-ph)
Field-induced upward bending of a magnetoelastomer cantilever residing on a horizontal plane: an unconventional cilium
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-30 20:00 EST
O. V. Stolbov, G. V. Stepanov, Yu. L. Raikher
The mechanical response of a cantilever made of a magnetoactive elastomer (MAE) that is positioned on a solid plane surface and is subjected to a uniform magnetic field is studied. The MAE is of the magnetically soft type, i.e., its filler particles become magnetized only in the presence of external field. Test observations with the applied field normal to the plane reveal two possible perturbed configurations of the cantilever: either its free end just bends upward or the cantilever folds into an arc, so that its free end does not detach from the supporting plane. The tests evidence that under cyclic variation of the field both deformation modes exhibit quite a wide bistability region, i.e., a magnetomechanical hysteresis takes place. Theoretical analysis shows that the cantilever bending scenario is indeed similar to that of the first-order transition. However, unlike the customary case, hereby the initial state never ceases to exist and remains stable against infinitesimal perturbations under arbitrary strong fields. Although this conclusion is valid only for an ideal situation, its nontrivial consequence is that the field value under which the transition to the bent state occurs is, in fact, unpredictable. The discovered effect is essentially different from the previously investigated behaviour of MAE cantilevers under an in-plane field; there the transition is of the second-order kind and is completely reversible. Finally, if to consider a horizontal MAE cantilever as an element of an assembly of magnetic cilia, it turns out that it behaves in the way opposite to that of conventional systems where in the initial state the MAE cilia stand normally to the supporting surface.
Soft Condensed Matter (cond-mat.soft)
Intermittent molecular motion and first passage statistics for the NMR relaxation of confined water
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-30 20:00 EST
Simon Gravelle, Benoit Coasne, Christian Holm, Alexander Schlaich
The structure and dynamics of fluids confined in nanoporous media differ from those in bulk, which can be probed using NMR relaxation measurements. We here show, using atomistic molecular dynamics simulations of water in a slit nanopore, that the behavior of the NMR relaxation rate, R1, with varying surface interaction and confinement strength can be estimated from the exchange statistics of fluid molecules between the adsorbed surface layer and the bulk region, where molecules undergo intermittent dynamics. We employ first return passage time calculations to quantify the molecular exchange statistics, thereby linking microscopic parameters of the confined fluid-such as adsorption time, pore size, and diffusion coefficient-to the NMR relaxation rate. This approach allows to predict and interpret the molecular relaxation of fluids at interfaces using merely concepts of statistical mechanics and can be generalized to closed and open geometries.
Soft Condensed Matter (cond-mat.soft), Chemical Physics (physics.chem-ph), Computational Physics (physics.comp-ph)
Effect of bismuth crystal orientations in Nernst thermomagnetic devices
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-30 20:00 EST
Alessandro Sola, Elena Sonia Olivetti, Adriano Di Pietro, Luca Martino, Vittorio Basso
In this work we report Nernst effect measurements in single crystal bismuth samples, with special emphasis on the characterization of the Nernst coefficient when the magnetic field, heat current and generated voltage are aligned along specific directions relative to the crystal axes. We found significant differences between the different orientations, reflecting the highly anisotropic electronic structure of bismuth and compatible with the Nernst characteristics obtained from polycrystalline samples. These results not only complement the experimental works published in the past but also underline the role of crystalline orientation in the context of transverse thermoelectric effects, towards an efficient design of thermomagnetic devices like the ordinary-Nernst-effect-based energy harvesters.
Materials Science (cond-mat.mtrl-sci)
11 pages, 5 figures
Universal transport at Lifshitz metal-insulator transitions in two dimensions
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-30 20:00 EST
We study the charge transport across a band-tuned metal-insulator transition in two dimensions. For high temperatures \(T\) and chemical potentials \(\mu\) far from the transition point, conduction is ballistic and the resistance \(R(T)\) verifies a simple one-parameter scaling relation. Here, we explore the limits of this semi-classical behaviour and study the quantum regime beyond, where scaling breaks down. We derive an analytical formula for the simplest Feynman diagram of the linear-response conductivity \(\sigma=1/R\) of a parabolic band endowed with a finite lifetime. Our formula shows excellent agreement for experiments for a field-tuned MoTe\(_2\)/WSe\(_2\) moiré bilayer, and can capture the quantum effects responsible for breaking the one-parameter scaling. We go on to discuss a fascinating prediction of our model: The resistance at the quantum-critical band-tuned Lifshitz point (\(\mu=T=0\)) has the universal value, \(R_L=(2 \pi h)/e^2\), per degree of freedom and this value is found to be compatible with experiment. Furthermore, we investigate whether two dimensional metal-insulator transitions driven by strong electron correlations or disorder can also be classified by their quantum-critical resistance and find that \(R_L\) may be useful in identifying predominantly interaction driven transitions.
Strongly Correlated Electrons (cond-mat.str-el)
7 pages plus Supplementary Information
Keldysh field theory approach to direct electric and thermoelectric currents in quantum dots coupled to superconducting leads
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-30 20:00 EST
Marco Uguccioni, Luca Dell'Anna
We study the transport properties of a quantum dot contacted to two superconducting reservoirs by means of the Keldysh field theory approach. We determine the direct current occurring at equilibrium and the electric and thermoelectric currents triggered when the system is driven out of equilibrium by a voltage or a temperature bias, also for a normal-quantum dot-superconductor junction. In particular, we derive and present for the first time the explicit expression of the thermoelectric current in a superconductor-quantum dot-superconductor junction for any values of the temperature difference between the superconducting leads. We show that in the linear response regime, in addition to the Josephson current, a weakly phase-dependent thermoelectric contribution occurs, providing that electron-hole symmetry is broken. Far from linearity, instead, other contributions arise which lead to thermoelectric effects, dominant at weak coupling, also in the presence of particle-hole symmetry.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Superconductivity (cond-mat.supr-con)
16 pages, 14 figures
Flexoelectricity causes surface piezoelectric-like effects in dielectrics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-30 20:00 EST
H. Mohammadi, F. Greco, D. Codony, I. Arias
In this paper we study the surface effects that bulk flexoelectric models in finite samples exhibit. We first show that when the body is infinite, flexoelectric materials do not exhibit electromechanical response under homogeneous loading. However, when the size of the body is finite, due to the symmetry-breaking nature of surfaces, homogeneous loading (mechanical or electrical) can cause an electromechanical response near the surfaces. We obtain closed-form solutions for finite samples under different electromechanical loading conditions, and show that the electromechanical response caused by the bulk flexoelectric effect is reminiscent of surface piezoelectricity, causing boundary layers in certain components of the strains and/or electric fields near the free surfaces.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
Supercurrent Diode Effect in Josephson Interferometers with Multiband Superconductors
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-30 20:00 EST
Yuriy Yerin, Stefan-Ludwig Drechsler, A. A. Varlamov, Francesco Giazotto, Mario Cuoco
We investigate nonreciprocal supercurrent phenomena in superconducting quantum interference devices (SQUIDs) that integrate Josephson junctions with single and multiband order parameters, which may exhibit time-reversal symmetry breaking. Our results show that the magnetic field can independently control both the amplitude and direction of supercurrent rectification, depending on the multiband characteristics of the superconductors involved. We analyze the effects of zero and antiphase ({}) pairing among different bands on the development of nonreciprocal effects and find that the rectification is not influenced by {}-pairing. Furthermore, we demonstrate that incorporating multiband superconductors that break time-reversal symmetry produces significant signatures in rectification. The rectification exhibits an even parity dependence on the magnetic field and the average rectification amplitude across quantum flux multiples does not equal zero. These findings indicate that magnetic flux pumping can be accomplished with time-reversal symmetry broken multiband superconductors by adjusting the magnetic field. Overall, our findings provide valuable insights for identifying and utilizing phases with broken time-reversal symmetry in multiband superconductors.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
11 pages, 4 figures. Comments, suggestions, missed citations are very welcome
Bounding multifractality by observables
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-01-30 20:00 EST
Tuomas I. Vanhala, Niklas Järvelin, Teemu Ojanen
Fractal dimensions have been used as a quantitative measure for structure of eigenstates of quantum many-body systems, useful for comparison to random matrix theory predictions or to distinguish many-body localized systems from chaotic ones. For chaotic systems at midspectrum the states are expected to be ``ergodic'', infinite temperature states with all fractal dimensions approaching 1 in the thermodynamic limit. However, when moving away from midspectrum, the states develop structure, as they are expected to follow the eigenstate thermalization hypothesis, with few-body observables predicted by a finite-temperature ensemble. We discuss how this structure of the observables can be used to bound the fractal dimensions from above, thus explaining their typical arc-shape over the energy spectrum. We then consider how such upper bounds act as a proxy for the fractal dimension over the many-body localization transition, thus formally connecting the single-particle and Fock space pictures discussed in the literature.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Quantum Physics (quant-ph)
11 pages, 6 figures
Topological Signatures of the Optical Bound on Maximal Berry Curvature: Applications to Two-Dimensional Time-Reversal-Symmetric Insulators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-30 20:00 EST
Unlike broken time-reversal symmetric (TRS) systems with a defined Chern number, directly measuring the bulk \(Z_{2}\) invariant and Berry curvature (if nonzero) in topological insulators and their higher-order topological families remains an unsolved problem. Here, based on the refined trace-determinant inequality (TDI) involving the trace and determinant of the quantum metric and maximal Berry curvature (MBC), we establish an optical bound on the MBC for two-dimensional TRS insulators. By utilizing (certain energy range of) experimental data on optical conductivity, one can identify topological signatures using the integrated optical bound. We illustrate our approach using three representative topological models: the Kane-Mele model, mirror-protected insulator, and quadrupole insulator. We find that the resulting momentum integration of the refined TDI provides an intrinsic relationship between quantum volume (QV) variations and topological phase transitions. We argue that double QV can be treated as an upper bound on the number of boundary states. Our findings offer a method for extracting the topological signatures of TRS insulators using optical conductivity data.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Topological insulator constrictions -- Dirac particles in a magneto-chiral box
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-30 20:00 EST
Michael Barth, Maximilian Fürst, Raphael Kozlovsky, Klaus Richter, Cosimo Gorini
We study magneto-transport through topological insulator nanowires shaped in the form of a constriction, as can be obtained by etching techniques. The magnetic field is coaxial, potentially turning the nanowire into a magneto-chiral junction. We show in a detailed analytical and numerical study that two main transport regimes emerge, depending on the central narrow region being short or long as compared to the magnetic length at the junction entrance and exit. In both cases the central region hosts Dirac-particle-in-a-box states due to magnetic confinement, whose conductance properties are strongly influenced by Landau levels at the ends of the constriction. Notably, in the low-energy regime only chiral states with a specific handedness can transport charge across the junction. Based on these properties and general symmetry considerations we argue that the shaped nanowire should exhibit strong magneto-chiral non-reciprocal transport beyond linear response. We employ a numerical tight-binding implementation of an effective 2D model on a non-homogeneous grid, capable of simulating samples of realistic sizes, and test its soundness against full simulations for scaled-down 3D topological insulator wires.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
10 pages, 10 figures
Bulk superconductivity in pressurized trilayer nickelate Pr4Ni3O10 single crystals
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-30 20:00 EST
Enkang Zhang, Di Peng, Yinghao Zhu, Lixing Chen, Bingkun Cui, Xingya Wang, Wenbin Wang, Qiaoshi Zeng, Jun Zhao
The discovery of superconductivity in pressurized bilayer and trilayer nickelates have generated significant interest. However, their superconducting properties are often dependent on sample quality and pressure conditions, complicating the interpretation of the underlying physics. Finding new systems with optimized bulk superconducting properties is therefore important for advancing our understanding of these materials. Unlike cupates, where trilayer compounds typically exhibit the highest transition temperature (Tc), the bilayer nickelate La3Ni2O7 has thus far outperformed the trilayer La4Ni3O10 in reported Tc. Whether the trilayer nickelates have achieved the optimal Tc remains unclear, with various scenarios suggesting different possibilities. Here, we report the discovery of bulk superconductivity in pressurized Pr4Ni3O10 single crystals, achieving a maximum onset Tc of 40.5 K at 80.1 GPa, significantly exceeding the 30 K observed in La4Ni3O10. The bulk nature of superconductivity is confirmed by zero resistance and a strong diamagnetic response bellow Tc with a superconducting volume fraction exceeding 80%. These findings establish trilayer nickelates as genuine bulk high-temperature superconductors, provide new insights into the mechanisms driving superconductivity, and point to a promising route toward further enhancing superconducting properties in nickelates.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
16 pages, 4 figures
Single crystal growth and physical characterization to fine tune YbIn1-xTxCu4 (T = Au, Ag) towards the critical endpoint of the valence transition
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-30 20:00 EST
Michelle Ocker, Bereket Ghebretinsae, Jan-Niklas Zimmermann, Sophie Würtele, Bernd Wolf, Alexandr Virovets, Michael Lang, Kristin Kliemt, Cornelius Krellner
Pure as well as Ag- and Au-substituted YbInCu\(_4\) single crystals were structurally and chemically characterized and investigated by means of heat capacity, magnetization, resistivity and ultrasonic measurements. We studied the influence of different compositions of the initial melt as well as of Au and Ag substitutions on the valence change and investigated whether this change occurs via a first-order phase transition or via crossover. We constructed a phase diagram of YbInCu\(_4\) as a function of various substitutions and show that the position of the critical endpoint of the valence transition depends on the substituent and on the conditions under which the samples were grown. Multiple thermal cycles through the first-order transition lead to a significant modification of the physical properties which clearly demonstrated the influence of defects in substituted YbInCu\(_4\).
Strongly Correlated Electrons (cond-mat.str-el)
Equilibrium and nonequilibrium behaviours of the Ising ferromagnetic thick cubic shell
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-30 20:00 EST
Ishita Tikader, Muktish Acharyya
We have studied the equilibrium and nonequilibrium behaviours of the Ising ferromagnetic thick cubic shell by Monte Carlo simulation. Our goal is to find the dependence of the responses on the thickness of the shell. In the equilibrium results, we found that the pseudo-critical temperature of ferro-para phase transition of thick cubic shell increases with the increase of the thickness following a hyperbolic tangent relation. In the nonequilibrium studies, the relaxation time has been found to decrease with the increase of the thickness of the cubic shell. Here three different regimes are found, namely rapid fall, plateau and linear region. The metastable behaviour has been studied also as another kind of non-equilibrium response. The metastable lifetime has been studied as function of the thickness of the cubic shell. A non-monotonic variation of metastable lifetime with the thickness of the shell is observed. A specified thickness for longest-lived metastability has been identified.
Statistical Mechanics (cond-mat.stat-mech)
10 pages Latex and 9 captioned pdf figures
Dynamic Competition between Cooper-Pair and Spin-Density-Wave Condensation
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-30 20:00 EST
B. Decrausaz, M. Pikulski, O. Ivashko, N. B. Christensen, J. Choi, L. Udby, Ch. Niedermayer, K. Lefmann, H. M. Rønnow, J. Mesot, J. Ollivier, T. Kurosawa, N. Momono, M. Oda, J. Chang, D. G. Mazzone
Quantum matter phases may co-exist microscopically even when they display competing tendencies. A fundamental question is whether such a competition can be avoided through the elimination of one phase while the other one condenses into the ground state. Here, we present a high-resolution neutron spectroscopy study of the low-energy spin excitations in the high-temperature superconductor La1.855Sr0.145CuO4. In the normal state, we find low-energy magnetic fluctuations at incommensurate reciprocal lattice positions where spin-density-wave order emerges at lower Sr concentration or at high magnetic fields. While these spin excitations are largely suppressed by the emergence of the superconducting spin gap, some low-energy magnetic fluctuations persist deep inside the superconducting state. We interpret this result in terms of a dynamic competition between superconductivity and magnetism, where superconductivity impedes the condensation of low-energy magnetic fluctuations through the formation of magnetically-mediated Cooper pairs.
Superconductivity (cond-mat.supr-con)
Cell Deformation Signatures along the Apical-Basal Axis: A 3D Continuum Mechanics Shell Model
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-30 20:00 EST
Jairo M. Rojas, Mayisha Z. Nakib, Vivian W. Tang, William M. Brieher, Sascha Hilgenfeldt
Two-dimensional (2D) mechanical models of confluent tissues have related the mechanical state of a monolayer of cells to the average perimeter length of the cell cross sections, predicting floppiness or rigidity of the material. For the well-studied system of in-vitro MDCK epithelial cells, however, we find experimentally that cells in mechanically rigid tissues display long perimeters characteristic of a floppy state in 2D models. We suggest that this discrepancy is due to mechanical effects in the third (apical-basal) dimension, including those caused by actin stress fibers near the basal membrane. To quantitatively understand cell deformations in 3D, we develop a continuum mechanics model of epithelial cells as elastic cylindrical shells, with appropriate boundary conditions reflecting both the passive confinement of neighboring cells and the active stress of actomyosin contractility. This formalism yields analytical solutions predicting cell cross sections along the entire cylinder axis. Deconvolution microscopy experimental data confirm the significant and systematic change in cell shape parameters in this apical-basal direction. In addition to providing a wealth of detailed information on deformation on the subcellular scale, the results of the approach alter our understanding of how active tissues balance requirements of their stiffness and integrity, suggesting they are more robust against loss of rigidity than previously inferred.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
9 pages, 5 figures. Supporting Information included in the same file (6 additional pages, 7 additional figures)
A machine-learning study of phase transitions in Ising, Blume-Capel, and Ising-metamagnet models
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-30 20:00 EST
Vasanth Kumar Babu, Rahul Pandit
We combine machine-learning (ML) techniques with Monte Carlo (MC) simulations and finite-size scaling (FSS) to study continuous and first-order phase transitions in Ising, Blume-Capel, and Ising-metamagnet spin models. We go beyond earlier studies that had concentrated on obtaining the correlation-length exponent \(\nu\). In particular, we show (a) how to combine neural networks (NNs), trained with data from MC simulations of Ising-type spin models on finite lattices, with FSS to obtain both thermal magnetic exponents \(y_t = 1/\nu\) and \(y_h\), respectively, at both critical and tricritical points, (b) how to obtain the NN counterpart of two-scale-factor universality at an Ising-type critical point, and (c) FSS at a first-order transition. We also obtain the FSS forms for the output of our trained NNs as functions of both the temperature and the magnetic field.
Statistical Mechanics (cond-mat.stat-mech), Computational Physics (physics.comp-ph)
Quantum oscillations in a dipolar excitonic insulator
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-30 20:00 EST
Phuong X. Nguyen, Raghav Chaturvedi, Bo Zou, Kenji Watanabe, Takashi Taniguchi, Allan H. MacDonald, Kin Fai Mak, Jie Shan
Quantum oscillations in magnetization or resistivity are a defining feature of metals subject to an external magnetic field. The phenomenon is generally not expected in insulators without a Fermi surface. The observations of quantum oscillations in Kondo insulating materials have provided a rare counterexample and attracted much theoretical interest. However, the magnetic oscillations in correlated insulators remain poorly understood. Here we report the observations of resistivity quantum oscillations in an excitonic insulator realized in Coulomb-coupled electron-hole double layers with gate-tunability that allows the phenomenon to be explored in a more controllable fashion than in bulk materials. When the cyclotron energy of the electrons or holes is tuned to be comparable to or larger than the exciton binding energy, recurring transitions between excitonic insulators and electron-hole decoupled quantum Hall states are observed. Compressibility measurements show an oscillatory exciton binding energy as a function of magnetic field and electron-hole pair density. Coulomb drag measurements further reveal the formation of excitons with finite angular momentum. Our results are qualitatively captured by mean-field theory calculations. The study demonstrates a new platform for studying quantum oscillations in correlated insulators.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
Thermal properties revisited in displacive ferroelectrics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-30 20:00 EST
The collective amplitude mode of the order parameter in displacive ferroelectrics, termed the ferron, represents the amplitude fluctuations of long-range ordered polarization. At temperatures well below phase transition temperature \(T_c\), the energy of ferron excitation is significantly gapped in the long-wavelength limit. As \(T_c\) is approached, this gap softens dramatically to minimal or gapless values, thereby should lead to a substantial contribution to thermal properties. In this context, we explore the role of ferrons in heat capacity and thermal transport by incorporating a microscopic self-consistent phase-transition theory for displacive ferroelectricity in contrast to the conventional treatment of attributing thermal properties solely to acoustic phonons. Using ferroelectric \(\rm{PbTiO}_{3}\) as a case study, we show that the softening of ferrons near the phase transition is essential to accurately capturing the experimental temperature and electric-field dependencies of thermal properties.
Materials Science (cond-mat.mtrl-sci)
10 pages, 11 figures
Unveiling Symmetry Instability induced by Topological Phase Transitions
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-30 20:00 EST
Liang Luo, Boqun Song, Genda Gu, Martin Mootz, Yongxin Yao, Ilias E. Perakis, Qiang Li, Jigang Wang
The symmetry-topology interplay dictates how to define order parameters and classify material ordered phases. However, current understanding of this interplay has been predominately approached from a one-sided perspective, with topological states being classified within the constraints imposed by specific fixed symmetries. Here we complete this full circle by demonstrating spontaneous symmetry breaking that results from a periodic alteration of topological phases induced by light in a centrosymmetric Dirac material ZrTe\(_5\). The distinguishing feature is the observation of robust correlation and striking anomalies in the fluence and temperature dependence of key transport this http URL, both shift current \(J_{\text{s}}\) and displacement current \(J_{\text{d}}\), arising from interband transition and infrared phonon driving, respectively, along with charge carrier pumping, exhibit similar behaviors. Second, they all peak at similar low pump fluence, followed by a subsequent reduction as the fluence further increases. This behavior cannot be explained by conventional energetically allowed, direct excitations. Third, all the three observables exhibit anomalies when they approach the topological phase transition temperature. These results highlight the unique low-energy pumping behaviors in ZrTe\(_5\), characterized by reversible fluence dependence and a 'hinge-like' interaction that connects various electronic and lattice observables, including phonons, charge carriers, and currents. Our findings, supported by model analysis, provide key insights into the fragility of crystalline (inversion) and time-reversal symmetries during the dynamics of topological phase transitions. This fragility drives spontaneous symmetry breaking, evidenced by the synchronized emergence of off-resonant infrared phonons and broken-symmetry photocurrents.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Self-organised dynamics and emergent shape spaces of active isotropic fluid surfaces
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-30 20:00 EST
Da Gao, Huayang Sun, Rui Ma, Alexander Mietke
Theories of self-organised active fluid surfaces have emerged as an important class of minimal models for the shape dynamics of biological membranes, cells and tissues. Here, we develop and apply a variational approach for active fluid surfaces to systematically study the nonlinear dynamics and emergent shape spaces such theories give rise to. To represent dynamic surfaces, we design an arbitrary Lagrangian-Eulerian parameterizations for deforming surfaces. Exploiting the symmetries imposed by Onsager relations, we construct a variational formulation that is based on the entropy production in active surfaces. The resulting dissipation functional is complemented by Lagrange multipliers to relax nonlinear geometric constraints, which allows for a direct computation of steady state solutions of surface shapes and flows. We apply this framework to study the dynamics of open fluid membranes and closed active fluid surfaces, and characterize the space of stationary solutions that corresponding surfaces and flows occupy. Our analysis rationalizes the interplay of first-order shape transitions of internally and externally forced fluid membranes, reveals degenerate regions in stationary shape spaces of mechanochemically active surfaces and identifies a mechanism by which hydrodynamic screening controls the geometry of active surfaces undergoing cell division-like shape transformations.
Soft Condensed Matter (cond-mat.soft)
29 pages, 7 figures