CMP Journal 2025-06-07
Statistics
Physical Review Letters: 3
Physical Review X: 2
arXiv: 78
Physical Review Letters
Spin and Density Modes in a Binary Fluid of Light
Research article | Cold atoms & matter waves | 2025-06-06 06:00 EDT
Clara Piekarski, Nicolas Cherroret, Tangui Aladjidi, and Quentin Glorieux
We report the experimental observation of spin and density modes in a binary mixture of superfluids of light. A miscible Bose-Bose mixture with repulsive interactions is realized by propagating the two circular polarization components of a laser through a nonlinear hot atomic vapor in the paraxial limit. By controlling the intensity and phase of both polarizations, we selectively excite the fundamental modes of the mixture. Using a Bragg-like spectroscopy technique, we measure the dispersion relation and identify two distinct branches with different sound velocities, corresponding to the spin and density modes. At high photon density, we observe a crossing of these branches, resulting from higher order nonlinear terms, linked to the saturation of the medium’s nonlinearity.
Phys. Rev. Lett. 134, 223403 (2025)
Cold atoms & matter waves, Kerr effect, Light-matter interaction, Quantum description of light-matter interaction, Quantum optics, Spinor Bose-Einstein condensates, Superfluidity
Role of Nematic Fluctuations on Superconductivity in ${\mathrm{FeSe}}{0.47}{\mathrm{Te}}{0.53}$ Revealed by Nuclear Magnetic Resonance under Pressure
Research article | Nematic order | 2025-06-06 06:00 EDT
Qing-Ping Ding, Juan Schmidt, Jose A. Moreno, Sergey L. Bud’ko, Paul C. Canfield, and Yuji Furukawa
The relationship between antiferromagnetic (AFM) spin fluctuations (SF), nematic fluctuations, and superconductivity (SC) has been central to understanding the pairing mechanism in iron-based superconductors (IBSCs). Iron chalcogenides, which hold the simplest crystal structure in IBSCs, provide a good platform to investigate the relationship. Here, we report $^{77}\mathrm{Se}$ and $^{125}\mathrm{Te}$ nuclear magnetic resonance studies of ${\mathrm{FeSe}}{0.47}{\mathrm{Te}}{0.53}$, which is located close to a nematic quantum critical point (QCP), under pressures up to 1.35 GPa. Both the superconducting critical temperature and AFMSF were found to be enhanced under pressure, which suggests a correlation between SC and AFMSF in ${\mathrm{FeSe}}{0.47}{\mathrm{Te}}{0.53}$. However, the contribution of AFMSF to SC in ${\mathrm{FeSe}}{0.47}{\mathrm{Te}}{0.53}$ was found to be much less compared to that in ${\mathrm{FeSe}}{1- x}{\mathrm{S}}{x}$, suggesting that nematic fluctuations play a dominant role in the SC in ${\mathrm{FeSe}}{1- x}{\mathrm{Te}}{x}$ around the nematic QCP.
Phys. Rev. Lett. 134, 226002 (2025)
Nematic order, Superconductivity, Iron-based superconductors, Strongly correlated systems, Nuclear magnetic resonance, Nuclear magnetic resonance relaxation rate
Radiative Stabilization of the Indenyl Cation: Recurrent Fluorescence in a Closed-Shell Polycyclic Aromatic Hydrocarbon
Research article | Laboratory studies of space & astrophysical plasmas | 2025-06-06 06:00 EDT
James N. Bull, Arun Subramani, Chang Liu, Samuel J. P. Marlton, Eleanor K. Ashworth, Henrik Cederquist, Henning Zettergren, and Mark H. Stockett
The harsh interstellar environment ought to destroy these carbon-rich molecules; experiments reveal their secret weapon.
Phys. Rev. Lett. 134, 228002 (2025)
Laboratory studies of space & astrophysical plasmas, Molecular dissociation, Electrostatic accelerators, Ions, Fluorescence
Physical Review X
Emergent Dimer-Model Topological Order and Quasiparticle Excitations in Liquid Crystals: Combinatorial Vortex Lattices
Research article | Disclinations & dislocations | 2025-06-06 06:00 EDT
Cuiling Meng, Jin-Sheng Wu, Žiga Kos, Jörn Dunkel, Cristiano Nisoli, and Ivan I. Smalyukh
Liquid crystals can be coaxed into hosting an easily reconfigurable lattice of vortices useful for information encoding.
Phys. Rev. X 15, 021084 (2025)
Disclinations & dislocations, Laser systems, Neural encoding, Neuromorphic computing, Topological defects, Topological order, Lattices, Liquid crystals, Magnetic monopoles, Metamaterials, Square lattice, Topological materials, Laser annealing, Optical tweezers, Spin lattice models
Phase Diagram of Extensive-Rank Symmetric Matrix Denoising beyond Rotational Invariance
Research article | Information & communication theory | 2025-06-06 06:00 EDT
Jean Barbier, Francesco Camilli, Justin Ko, and Koki Okajima
Bayesian-optimal methods for denoising factorized matrices of extensive rank reveal two phases: one where matrix structure does not affect performance and another where it becomes crucial.
Phys. Rev. X 15, 021085 (2025)
Information & communication theory, Stochastic inference, Disordered systems, Random matrix theory
arXiv
polyBART: A Chemical Linguist for Polymer Property Prediction and Generative Design
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-06 20:00 EDT
Anagha Savit, Harikrishna Sahu, Shivank Shukla, Wei Xiong, Rampi Ramprasad
Designing polymers for targeted applications and accurately predicting their properties is a key challenge in materials science owing to the vast and complex polymer chemical space. While molecular language models have proven effective in solving analogous problems for molecular discovery, similar advancements for polymers are limited. To address this gap, we propose polyBART, a language model-driven polymer discovery capability that enables rapid and accurate exploration of the polymer design space. Central to our approach is Pseudo-polymer SELFIES (PSELFIES), a novel representation that allows for the transfer of molecular language models to the polymer space. polyBART is, to the best of our knowledge, the first language model capable of bidirectional translation between polymer structures and properties, achieving state-of-the-art results in property prediction and design of novel polymers for electrostatic energy storage. Further, polyBART is validated through a combination of both computational and laboratory experiments. We report what we believe is the first successful synthesis and validation of a polymer designed by a language model, predicted to exhibit high thermal degradation temperature and confirmed by our laboratory measurements. Our work presents a generalizable strategy for adapting molecular language models to the polymer space and introduces a polymer foundation model, advancing generative polymer design that may be adapted for a variety of applications.
Soft Condensed Matter (cond-mat.soft)
Magnetophoresis of paramagnetic nanoparticles in suspensions under magnetic field gradients
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Peter Rassolov, Jamel Ali, Theo Siegrist, Munir Humayun, Hadi Mohammadigoushki
We systematically investigate the magnetophoresis of weakly paramagnetic manganese oxide nanoparticles under nonuniform magnetic fields using a combination of experiments and multiphysics numerical simulations. Experiments were conducted in a closed cuvette exposed to a nonuniform magnetic field generated by an electromagnet, covering a wide range of particle concentrations 25-200 mgL and magnetic field gradients 0-110 T2m. The experimental results reveal that paramagnetic manganese oxide nanoparticles exhibit significant magnetophoretic behavior, leading to particle depletion within the cuvette. The depletion rate is independent of the initial particle concentration but strongly depends on the magnetic field gradient. At low magnetic field gradients, magnetophoresis progresses slowly, while at higher gradients, the particle depletion rate increases significantly before stabilizing. Transient concentration gradients emerge within the cuvette during magnetophoresis, which we hypothesize are driven by magnetic Grashof numbers near unity. When magnetic Grashof is beyond 1, the formation of concentration gradients induces bulk fluid flows that accelerate particle capture at regions of maximum magnetic field strength. In systems where magnetophoresis opposes sedimentation, particle depleted regions form when the ratio of magnetic to gravitational Peclet numbers exceeds 1. The numerical simulations suggest formation field induced aggregation for manganese oxide nanoparticles with radii of 130 nm or larger. These insights highlight the potential of magnetic separation for sustainable metal recovery, offering a scalable and environmental friendly solution for recycling critical materials from spent electronics.
Materials Science (cond-mat.mtrl-sci)
Griffiths phases in structurally disordered CeRhSn: Experimental evidence and theoretical modeling
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-06 20:00 EDT
Andrzej Ślebarski, Maciej M. Maśka
Our report paves the way for insight into a structural disorder and its impact on the physical properties of strongly correlated electron systems (SCESs). In a critical regime, each perturbation, e.g., disorder due to structural defects or doping, can have a significant effect on the nature of the quantum macrostate of these materials. For a select group of SCESs, we have empirically documented the Griffiths singularity, as exemplified by CeRhSn, which exhibits non-Fermi-liquid characteristics in susceptibility and specific heat. Our numerical analysis has supported the Griffiths phase scenario for CeRhSn and has revealed that its dc magnetic susceptibility is strongly dependent on the size of inhomogeneous magnetic particles that form in these materials. In the presence of strong disorder, we have proposed a magnetic phase diagram for CeRhSn. The classical Griffiths phase has been identified in the temperature range below the onset temperature of $ T_G$ ~ 220 K, while the quantum Griffiths phase with non-Fermi liquid behavior emerges below the quantum critical temperature of $ T_Q$ ~ 6 K. The phase diagram developed in this study bears notable similarities to the scenario previously proposed by Vojta for magnetic quantum phase transitions in disordered metals.
Strongly Correlated Electrons (cond-mat.str-el)
11 pages, 10 figures
Phys. Rev. B 111, 235106 (2025)
Geometric Bloch oscillations and transverse displacement in flat band systems
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
Jing-Xin Liu, Giandomenico Palumbo, Marco Di Liberto
We investigate transport phenomena and dynamical effects in flat bands where the band dispersion plays no role. We show that wavepackets in geometrically non-trivial flat bands can display dynamics when inhomogeneous electric fields are present. This dynamics is revealed both for the wavepacket trajectory and for its variance, for which we derive semiclassical equations extended to the non-Abelian case. Our findings are tested in flat band models in one- and two-dimensional lattices where the dynamics is solely determined by geometric effects, in the absence of band dispersion. In particular, in the one-dimensional case, we show the existence of Bloch oscillations for the wavepacket position and for the wavepacket variance, whereas in the two-dimensional case we observe a transverse displacement of the wavepacket in the absence of Berry curvature. This work paves the way for understanding quantum-geometry-induced dynamical effects in flat band materials and also opens the possibility for their observation with synthetic matter platforms.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Gases (cond-mat.quant-gas)
8 + 11 pages, 5 + 2 figures
Emergent gravity and gravitational lensing in quantum materials
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
Yugo Onishi, Nisarga Paul, Liang Fu
We show that an effective gravitational field naturally emerges in quantum materials with long-wavelength spin (or pseudospin) textures. When the itinerant electrons’ spin strongly couples to the background spin texture, it effectively behaves as a spinless particle in a curved space, with the curvature arising from quantum corrections to the electron’s spin orientation. The emergent gravity gives rise to the electron lensing effect, an analog of the gravitational lensing. Our work shows that novel ``gravitational’’ phenomena generically appear in quantum systems due to nonadiabaticity, opening new research directions in quantum physics.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
7 pages (including references and 3 figures) + Appendix (8 pages and 5 figures)
Magnetic field-free braiding and nontrivial fusion of Majorana bound states in high-temperature planar Josephson junctions
New Submission | Superconductivity (cond-mat.supr-con) | 2025-06-06 20:00 EDT
Pankaj Sharma, Narayan Mohanta
Demonstration of non-Abelian statistics of zero-energy Majorana bound states (MBS) is crucial for long-sought-after decoherence-free topological quantum computing. The ability to move the MBS on a two-dimensional platform such as a planar Josephson junction is practically constrained by a fixed direction of applied magnetic field. In addition, the detrimental effects of the magnetic field on proximity-induced superconductivity in semiconductor-superconductor heterostructures is an outstanding problem for the realization of topological superconductivity. Here we show that these problems can be solved in a planar Josephson junction coupled to a skyrmion crystal, which generates the MBS without the need of any external magnetic field, phase biasing, and Rashba spin-orbit coupling. Using a high-temperature superconductor having $ d$ -wave pairing symmetry, we confirm that our planar junction can support the MBS at high temperatures. We propose protocols for performing non-trivial fusion, exchange and non-Abelian braiding of multiple MBS in our field-free platforms. The proposed geometries and MBS movement protocols open a path towards successful experimental detection of the MBS via confirmation of their non-Abelian statistics.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
6 pages, 4 figures
The Luttinger Count is the Homotopy not the Physical Charge: Generalized Anomalies Characterize Non-Fermi Liquids
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-06 20:00 EDT
Gabriele La Nave, Jinchao Zhao, Philip W. Phillips
We show that the Luttinger-Ward functional can be formulated as an operator insertion in the path integral and hence can be thought of as a generalized symmetry. The key result is that the associated charge, always quantized, defines the homotopy, not the physical charge. The disconnect between the two arises from divergences in the functional or equivalently zeros of the single-particle Green function. Such divergences produce an anomaly of the triangle-diagram type. As a result of this anomaly, we are able to account for the various deviations\cite{rosch,dave,altshuler,osborne,l3,l5} of the Luttinger count from the particle density. As a consequence, non-Fermi liquids can be classified generally by the well known anomaly structures in particle physics. Charges descending from generalized symmetries, as in the divergence of the Luttinger-Ward functional, are inherently non-local, their key experimental signature.
Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Theory (hep-th)
6 pages
Intra-unit-cell singlet pairing mediated by altermagnetic fluctuations
New Submission | Superconductivity (cond-mat.supr-con) | 2025-06-06 20:00 EDT
Yi-Ming Wu, Yuxuan Wang, Rafael M. Fernandes
We investigate the superconducting instabilities induced by altermagnetic fluctuations. Because of the non-trivial sublattice structure of the altermagnetic order, shorter-range and longer-range fluctuations favor qualitatively different types of pairing states. Specifically, while the latter stabilize a standard spin-triplet $ p$ -wave state, just like ferromagnetic fluctuations, the former leads to intra-unit-cell pairing, in which the Cooper pairs are formed by electrons from different sublattices. The symmetry of the intra-unit-cell gap function can be not only $ p$ -wave, but also spin-singlet $ s$ -wave and $ d$ -wave, depending on the shape of the Fermi surface. We also show that coexistence with altermagnetic order promotes intrinsic non-trivial topology, such as protected Bogoliubov Fermi surfaces and higher-order topological superconductivity. Our work establishes the key role played by sublattice degrees of freedom in altermagnetic-fluctuation mediated interactions.
Superconductivity (cond-mat.supr-con)
Main text: 7 pages + 3 figures; Supplementary material: 16 pages + 6 figures
Substrate pre-sputtering for layer-by-layer van der Waals epitaxy of 2D materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
A. Rajan, M. Ramirez, N. Kushwaha, S. Buchberger, M. McLaren, P.D.C. King
Two-dimensional transition metal chalcogenides, with their atomically layered structure, favourable electronic and mechanical properties, and often strong spin-orbit coupling, are ideal systems for fundamental studies and for applications ranging from spintronics to optoelectronics. Their bottom-up synthesis via epitaxial techniques such as molecular-beam epitaxy (MBE) has, however, proved challenging. Here, we develop a simple substrate pre-treatment process utilising exposure to a low-energy noble gas plasma. We show how this dramatically enhances nucleation of an MBE-grown epilayer atop, and through this, realise a true layer-by-layer growth mode. We further demonstrate the possibility of tuning the resulting growth dynamics via control of the species and dose of the plasma exposure.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
6 pages, 3 figures
Om-Theory of Macroscopic Electromagnetism: Greener Vibes for Isotropy-Broken Media
New Submission | Other Condensed Matter (cond-mat.other) | 2025-06-06 20:00 EDT
The applicability ranges of macroscopic and microscopic electromagnetisms are opposite. While microscopic electromagnetism deals with point sources, singular fields, and discrete atomistic materials, macroscopic electromagnetism concerns smooth average distributions of sources, fields, and homogenized effective metamaterials. Greens function method - GFM - involves finding fields of point sources and applying superposition principle to find fields of distributed sources. When utilized to solve microscopic problems GFM is perfectly within the applicability range. Extension of GFM to simple macroscopic problems is convenient, but not fully logically sound, since point sources and singular fields are technically not a subject of macroscopic electromagnetism. This explains the difficulty of both finding the Greens functions and applying superposition principle in complex isotropy-broken media, which are very different from microscopic environments. In this manuscript, we lay out a path to solution of macroscopic Maxwells equations for distributed sources bypassing GFM, by introducing inverse approach and a method based on Om-potential which we describe here. To the researchers of electromagnetism this provides access to powerful analytical tools and a broad new space of solutions for Maxwells equations.
Other Condensed Matter (cond-mat.other), Materials Science (cond-mat.mtrl-sci), Optics (physics.optics)
10 pages, 4 figures
Substrate matters: Coupled phonon modes of a spherical particle on a substrate probed with EELS
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Ka Yin Lee, Elliot K. Beutler, Tifany Q. Crisolo, David J. Masiello, Maureen J. Lagos
Using vibrational electron energy loss spectroscopy (vib-EELS) combined with numerical modeling, we investigate the physical mechanisms governing the phonon coupling between a spherical particle sustaining multipolar surface phonon modes and an underlying thin film. Depending upon their dielectric composition, a variety of hybrid phonon modes arise in the EEL spectrum due to the interaction between polarization charges in the particle and film. Mirror charge effects and phonon mode hybridization are the active mechanisms acting on dielectric and metallic-type films, respectively. Processes beyond dipole-dipole interactions are required to describe the sphere-film coupling.
Materials Science (cond-mat.mtrl-sci)
13 pages, 4 figures, 6 appendices
Enhanced strain rate sensitivity due to platelet linear complexions in Al-Cu
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Pulkit Garg, Daniel S. Gianola, Timothy J. Rupert
Platelet array linear complexions have been predicted in Al-Cu, with notable features being dislocation faceting and climb into the precipitate, both of which should impact plasticity. In this study, we examine the strain rate dependence of strength for platelet linear complexions using atomistic simulations, with classical precipitate strengthening through particle cutting and particle bowing used as baseline comparisons. Dislocation segments with edge character must climb down from the platelet structures prior to the commencement of glide, introducing a significant time-dependent barrier to plastic deformation. Consequently, the strain rate sensitivity of strength for the platelet linear complexions system was found to be up to five times higher than that of classical precipitation strengthening mechanisms.
Materials Science (cond-mat.mtrl-sci)
Direct Joule-Heated Non-Equilibrium Synthesis Enables High Performing Thermoelectrics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Chenguang Zhang, Jose Recatala-Gomez, Zainul Aabdin, Yi Jiang, Luyang Jiang, Sze Yu Tan, Hong Liu, Yuting Qian, Coryl Jing Jun Lee, Sabrine Hachmioune, Vaishali Taneja, Anqi Sng, Pawan Kumar, Haiwen Dai, Zhiqian Lin, Weng Weei Tjiu, Fengxia Wei, Qianhong She, D. V. Maheswar Repaka, David Scanlon, Kanishka Biswas, Yee Kan Koh, Kedar Hippalgaonkar
High-throughput synthesis of bulk inorganic materials is crucial for accelerating functional materials discovery but is hindered by slow, energy-intensive solid-state methods. We introduce Direct Joule-Heated Synthesis (DJS), a rapid, single-step and scalable solid-state synthesis technique achieving a $ 10^5$ -fold speedup and 20,000x energy efficiency improvement over conventional synthesis. DJS enables the synthesis of dense, bulk chalcogenides ($ \mathrm{Bi_{0.5}Sb_{1.5}Te_3}$ , $ \mathrm{AgSbTe_2}$ ), achieving a zT of 2.3 at 573 K in optimally Cd/Se co-doped $ \mathrm{AgSbTe_2}$ , one of the highest for polycrystalline materials at this temperature. DJS enables optimal co-doping and rapid, non-equilibrium solidification, producing lamellar microstructures, interfacial regions, and cation-ordered nanodomains that scatter all-scale phonons, achieving ultralow lattice thermal conductivity (~0.2 $ W m^{-1} K^{-1}$ at 573 K). DJS establishes a new benchmark for scalable and fast synthesis, accelerating functional material discovery.
Materials Science (cond-mat.mtrl-sci)
Interfacial Energy Gradients Drive Coalescence of Supported Nanoparticles
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Cheng-Yu Chen, Duncan Burns, Peter W. Voorhees, Eric A. Stach
Understanding and controlling nanoparticle coalescence is crucial for applications ranging from catalysis to nanodevice fabrication, yet the behavior of nanoparticles on dynamically evolving, heterogeneous substrates remains poorly understood. Here, we employ in situ transmission electron microscopy to investigate platinum (Pt) nanoparticle dynamics on silicon nitride (SiN$ _x$ ) substrates where localized crystalline silicon (Si) nanodomains are deliberately formed via electron beam irradiation at $ 800^\circ$ C. We observe that Pt nanoparticles in contact with these Si pads transform into a more mobile platinum silicide (Pt$ _3$ Si) phase. Strikingly, these Pt$ _3$ Si nanoparticles exhibit pronounced directional migration away from the Si pads, driven by interfacial energy gradients, rather than undergoing stochastic Brownian motion. This directed movement fundamentally dictates coalescence pathways, leading to either enhanced sintering when particles are channeled together or inhibited coalescence when Si pads act as repulsive barriers. Our findings reveal that local substrate chemistry and the resulting interfacial energy landscapes can dominate over initial particle size or proximity in controlling solid-state nanoparticle migration and assembly. This work provides insights into how substrate heterogeneity can be used to direct nanoparticle behavior, challenging conventional coalescence models and offering pathways for the rational design of supported nanomaterials.
Materials Science (cond-mat.mtrl-sci)
Chern insulators in two and three dimensions: A global perspective
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
We introduce a second-quantized continuum model for bulk Chern insulators wherein the Hamiltonian features a static magnetic field that has the periodicity of the crystal’s lattice and spontaneously breaks time-reversal symmetry even in the electronic ground state at zero temperature. The topological invariants characterizing the bulk band structure of Chern insulators in both two and three dimensions are written entirely in terms of the quantities in this Hamiltonian and are globally defined across the Brillouin zone. We discuss the symmetry properties of these systems, including the discrete symmetries in the “tenfold way” classification scheme, inversion symmetry, and gauge transformations. We also study the long-wavelength response of Chern insulators to both static and finite-frequency electric fields in the linear regime, using an expression for the conductivity tensor that was derived in recent work. And we discuss how our global expressions for the Chern invariants are modified when electron spin is considered.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Neural Object Detection for 4D STEM: High-Throughput Sub-Pixel Electron Diffraction Pattern Recognition
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
High-throughput analysis of multidimensional transmission electron microscopy (TEM) datasets remains a significant challenge, limiting the broader impact on strategic materials research. Conventional workflows typically involve sequential, modular processing steps that necessitate extensive manual intervention and offline parameter tuning. In this work, we introduce an end-to-end post-processing framework for large-scale four-dimensional scanning TEM (4D-STEM) datasets, built around a highly efficient neural network-based object detection model. Central to our method is a sub-pixel accurate object center localization algorithm, which serves as the foundation for high-precision and high-throughput analysis of electron diffraction patterns. We demonstrate a strain measurement precision of 5x$ 10^{-4}$ , quantified by the standard deviation of strain values within the strain-free Si substrate of a Si/SiGe multilayer TEM sample. Furthermore, by implementing an asynchronous, non-blocking object detection workflow, we achieve speeds exceeding 100 frames per second (fps), substantially accelerating the crystallographic phase identification and strain mapping in complex multiphase metallic alloys.
Materials Science (cond-mat.mtrl-sci)
Topology induced modifications in the critical behavior of the Yaldram Khan catalytic reaction model
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-06 20:00 EDT
Paulo F. Gomes, Henrique A. Fernandes, Roberto da Silva
In this work, we investigated how the use of complex networks as catalytic surfaces can affect the phase diagram of the Yaldram-Khan model, as well as how the order of the phase transitions present in the seminal work behaves when the randomness is added to the model. The study was conducted by taking into consideration two well-known random networks, the Erdos-Renyi network (ERN), with its long-range randomness, and the random geometric graph (RGG), with its spatially constrained randomness. We perform extensive steady-state Monte Carlo simulations assuming the NO dissociation rate is equal to 1 and show the behavior of the reactive window as function of the average degree of the networks. Our results also show that, different from the ERN, which preserves the nature of the phase transitions of the original model for all considered average degrees, the RGG seems to have two second-order phase transitions for small values of average degree.
Statistical Mechanics (cond-mat.stat-mech)
19 pages, 9 figures
It’s about time: a thermodynamic information criterion (TIC)
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-06 20:00 EDT
Brendan Lucas, Google Gemini 2.5 Pro Preview 05-06
Useful chemical processes often involve a desired steady state probability distribution, equilibrium or not, from which product is extracted. Given many different ways to attain the same steady state, which candidate “loses” the least in terms of time and energy? A scalar thermodynamic information criterion (TIC), inspired by AIC, assigns lower values to chemical processes with less estimated “loss” to generate the same desired steady state. As an element of thermodynamic machine learning, TIC naturally extends statistical objective optimization into the realm of chemical physics.
Statistical Mechanics (cond-mat.stat-mech)
Investigation of the Paramagnetic State of the Kagome Kondo Lattice Compound YbV$_6$Sn$_6$: a $^{51}$V Nuclear Magnetic Resonance Study
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-06 20:00 EDT
S. Park, H. Sakai, S. Hosoi, S. M. Thomas, S. Kambe, Y. Tokunaga, A. P. Dioguardi, J. D. Thompson, F. Ronning, M. Kimata, T. Furukawa, T. Sasaki, E. D. Bauer, M. Hirata
YbV$ _6$ Sn$ 6$ is a recently discovered kagome-lattice metal that orders at $ T{\rm N}\approx0.4$ K. Its layered structure combines a triangular Kondo lattice of Yb$ ^{3+}$ ions with vanadium-based kagome planes, which may host an interplay between strong correlations and band topology. We report a $ ^{51}$ V nuclear magnetic resonance (NMR) study of the paramagnetic state of YbV$ _6$ Sn$ 6$ . Detailed field-angular dependence of single-crystal NMR spectra determined the principal-axis directions of the electric field gradient tensor at the $ ^{51}$ V sites, as well as their nuclear quadrupole frequency, $ \nu{\rm Q}$ , and asymmetry parameter, $ \eta$ . The Knight shift, $ K$ , was measured for different field orientations, and the analysis of $ K$ against magnetic susceptibility to extract anisotropic hyperfine couplings. Accurate spectral assignments further enabled measurements of the nuclear spin-lattice relaxation rate, $ 1/T_1$ , for both in-plane and out-of-plane field directions. The temperature dependence of $ 1/T_1$ shows that out-of-plane spin fluctuations are suppressed below $ \sim$ 20K, whereas in-plane fluctuations are markedly enhanced, which might be understood by thermal depopulation of the low-lying crystalline electric field excited state. The notable anisotropy in $ 1/T_1$ indicates that the paramagnetic state of YbV$ _6$ Sn$ _6$ is strongly affected by in-plane spin dynamics.
Strongly Correlated Electrons (cond-mat.str-el)
A brief history of dislocations in ceramics: From Steinsalz to quantum wires
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Dislocations in ceramics have enjoyed a long yet underappreciated research history. This brief historical overview and reflection on the current challenges provides new insights into using this line defect as a rediscovered tool for engineering functional ceramics.
Materials Science (cond-mat.mtrl-sci)
American Ceramic Society Bulletin, 2025
Nonreciprocal superconducting critical currents with normal state field trainability in kagome superconductor CsV3Sb5
New Submission | Superconductivity (cond-mat.supr-con) | 2025-06-06 20:00 EDT
Jun Ge, Xiaoqi Liu, Pinyuan Wang, Haowen Pang, Qiangwei Yin, Hechang Lei, Ziqiang Wang, Jian Wang
Determining time-reversal symmetry (TRS) and chirality in the superconducting state and its relation to the symmetry and topology in the normal state are important issues in modern condensed matter physics. Here, we report the observation of nonreciprocal superconducting critical currents (Ic) at zero applied magnetic field: Ic exhibits different values in opposite directions, in both flakes and micro-bridges of the kagome superconductor CsV3Sb5. Such spontaneous nonreciprocity requires TRS and inversion symmetry breakings. We find that the direction of asymmetry changes randomly in repeated sample heating to 300 K and cooling into the zero-resistance state, consistent with the expected behavior arising from spontaneous TRS breaking. Crucially, on applying a perpendicular magnetic field at 300 K, above the charge density wave (CDW) transition at TCDW in this compound and removing it to zero well above the superconducting onset critical temperature (Tc), the direction of the Ic asymmetry consistently flips on changing the direction of the field. This magnetic field training ascertains that the CDW state above the superconducting transition temperature may also break the Z2 TRS and has a macroscopic directionality which can be changed by a uniform training field. The symmetry breaking continues into the superconducting state and gives rise to the nonreciprocal superconducting critical currents. These results indicate the loop-current CDW normal state with topological features in CsV3Sb5. Our observations provide direct evidence for the TRS breaking in kagome superconductor CsV3Sb5, and offer new insights into the mechanism of TRS breaking in kagome superconductors.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Correlating Superconducting Qubit Performance Losses to Sidewall Near-Field Scattering via Terahertz Nanophotonics
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
Richard H. J. Kim, Samuel J. Haeuser, Joong-Mok Park, Randall K. Chan, Jin-Su Oh, Thomas Koschny, Lin Zhou, Matthew J. Kramer, Akshay A. Murthy, Mustafa Bal, Francesco Crisa, Sabrina Garattoni, Shaojiang Zhu, Andrei Lunin, David Olaya, Peter Hopkins, Alex Romanenko, Anna Grassellino, Jigang Wang
Elucidating dielectric losses, structural heterogeneity, and interface imperfections is critical for improving coherence in superconducting qubits. However, most diagnostics rely on destructive electron microscopy or low-throughput millikelvin quantum measurements. Here, we demonstrate noninvasive terahertz (THz) nano-imaging/-spectroscopy of encapsulated niobium transmon qubits, revealing sidewall near-field scattering that correlates with qubit coherence. We further employ a THz hyperspectral line scan to probe dielectric responses and field participation at Al junction interfaces. These findings highlight the promise of THz near-field methods as a high-throughput proxy characterization tool for guiding material selection and optimizing processing protocols to improve qubit and quantum circuit performance.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Quantum Physics (quant-ph)
Ultrafast Orbital-Selective Photodoping Melts Charge Order in Overdoped Bi-based Cuprates
New Submission | Superconductivity (cond-mat.supr-con) | 2025-06-06 20:00 EDT
Xinyi Jiang, Qizhi Li, Qingzheng Qiu, Li Yue, Junhan Huang, Yiwen Chen, Byungjune Lee, Hyeongi Choi, Xingjiang Zhou, Tao Dong, Nanlin Wang, Hoyoung Jang, Yingying Peng
High-temperature superconductivity in cuprates remains one of the enduring puzzles of condensed matter physics, with charge order (CO) playing a central yet elusive role, particularly in the overdoped regime. Here, we employ time-resolved X-ray absorption spectroscopy and resonant X-ray scattering at a free-electron laser to probe the transient electronic density of states and ultrafast CO dynamics in overdoped (Bi,Pb)$ _{2.12}$ Sr$ _{1.88}$ CuO$ _{6+\delta}$ . We reveal a striking pump laser wavelength dependence - the 800 nm light fails to suppress CO, whereas the 400 nm light effectively melts it. This behavior originates from the fact that 400 nm photons can promote electrons from the Zhang-Rice singlet band to the upper Hubbard band or apical oxygen states, while 800 nm photons lack the energy to excite electrons across the charge-transfer gap. The CO recovery time ($ \sim$ 3 ps) matches that of the underdoped cuprates, indicating universal electronic instability in the phase diagram. Additionally, melting overdoped CO requires an order-of-magnitude higher fluence highlighting the role of lattice interactions. Our findings demonstrate orbital-selective photodoping and provide a route to ultrafast control of emergent quantum phases in correlated materials.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
13 pages, 11 figures, comments are welcome
Derivation of a non-stoichiometric 1/1 quasicrystal approximant from a stoichiometric 2/1 quasicrystal approximant and maximization of magnetocaloric effect
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Farid Labib, Hiroyuki Takakura, Asuka Ishikawa, Takenori Fujii, Ryuji Tamura
The present research introduces a novel strategy for tuning magnetic properties by overcoming the compositional limitation of stoichiometric intermetallic compounds via extension of their stability into a new dimension within valence electron-per-atom (e/a) parameter space. Focusing on approximant crystals (ACs), a “double hetero-valent elemental substitution” is employed in a stoichiometric Ga-Pt-Gd 2/1 AC whereby e/a is lowered from 1.92 to 1.60. Through this approach a new family of stable Ga-based Tsai-type 1/1 ACs with exceptionally wide composition stability within e/a space is derived. Remarkably, magnetic ground state is altered from initially spin-glass to ferromagnetic (FM) with second order phase transition and mean-field-like critical behavior. More importantly, through this strategy, the isothermal magnetic entropy change enhanced significantly and reached a maximum value of -8.7 J/K mol-Gd under a 5 T magnetic field change, even comparable to leading rare-earth magnetocaloric materials including RCo2 phases. These findings demonstrate the high potential of a double hetero-valent elemental substitution for tailoring magnetic properties and magnetocaloric response in stoichiometric compounds, offering a new pathway for designing high-performance magnetic refrigeration materials even beyond the quasicrystals and ACs.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
5 figures
Buried unstrained Ge channels: a lattice-matched platform for quantum technology
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
Davide Costa, Karina Hudson, Patrick Del Vecchio, Lucas E. A. Stehouwer, Alberto Tosato, Davide Degli Esposti, Mario Lodari, Stefano Bosco, Giordano Scappucci
Ge and Si strained quantum wells have enabled the most advanced spin-qubit quantum processors, but they are deposited on defective, metamorphic SiGe substrates, which may impact device performance and scaling. Here we introduce an alternative platform, based on a heterojunction between unstrained Ge and a strained SiGe barrier, which is lattice-matched to a Ge substrate. In a structure with a 52-nm-thick strained SiGe barrier, we demonstrate a low-disorder two-dimensional hole gas with a high-mobility of 1.33$ \times$ 10$ ^5$ cm$ ^2$ /Vs and a low percolation density of 1.4(1)$ \times$ 10$ ^1$ ^0$ cm$ ^-$ ^2$ . Quantum transport measurements show that confined holes have a strong density-dependent in-plane effective mass and out-of-plane $ g$ -factor, pointing to a significant heavy-hole–light-hole mixing in agreement with theory. The expected strong spin-orbit interaction, possibility of isotopic purification, and ability to host superconducting pairing correlations make this platform appealing for fast quantum hardware and hybrid quantum systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Stochastic thermodynamics for classical non-Markov jump processes
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-06 20:00 EDT
Kiyoshi Kanazawa, Andreas Dechant
Stochastic thermodynamics investigates energetic/entropic bounds in small systems, such as biomolecular motors, chemical-reaction networks, and quantum nano-devices. Foundational results, including the second law and thermodynamic uncertainty relations, predominantly rely on the Markov assumption – neglecting history dependence of physical systems. However, while physicists recognise that the Markov assumption is dubious in real experimental setups, extending stochastic thermodynamics to general non-Markov systems has proven challenging due to their mathematical complexity. Here we establish the general theory of stochastic thermodynamics for arbitrary classical non-Markov jump processes. We introduce a key technique, called the {\it Fourier embedding}, which converts any non-Markov jump process into the Markov field dynamics of auxiliary Fourier modes. This approach yields the necessary and sufficient condition for time-reversal symmetry and enables the derivation of the second law for our non-Markov systems. Our framework accommodates diverse non-Markovian dynamics in realistic experimental setups and offers a guiding principle for physics-informed modelling of history-dependent fluctuations.
Statistical Mechanics (cond-mat.stat-mech)
5+3 pages, 4 figures
Numerical Investigation of Stub Length Influence on Dispersion Relations and Parity Effect in Aharonov-Bohm Rings
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Aharonov-Bohm (AB) rings with side-attached stubs are model systems for quantum-interference studies in mesoscopic physics. The geometry of such systems, particularly the ratio of stub length ($ v$ ) to ring circumference ($ u$ ), can significantly alter their electronic states. In this work, we solve Deo’s transcendental mode-condition equation (Eq. 2.15 from Deo, 2021 [Deo2021]) numerically – using Python’s NumPy and SciPy libraries – for ring-stub geometries with $ v/u = 0.200, 0.205,$ and $ 0.210$ to generate dispersion relations ($ ku$ vs. $ \Phi/\Phi_{0}$ ) and the underlying function $ \text{Re}(1/T)$ . We find that changing $ v/u$ shifts several of the six lowest calculated dispersion branches, with $ \Delta(ku)$ up to approximately $ 0.34$ for the 6th branch at $ \Phi=0$ when comparing $ v/u=0.200$ and $ v/u=0.210$ . This also alters gap widths. Notably, for $ v/u=0.205$ and $ v/u=0.210$ , the 5th and 6th consecutive calculated modes both exhibit paramagnetic slopes near zero Aharonov-Bohm flux, indicating the parity breakdown initiates at or below $ v/u=0.205$ . This directly demonstrates a breakdown of the simple alternating parity effect predicted by Deo (2021) [Deo2021]. These results highlight the sensitivity of mesoscopic ring spectra to fine-tuning of stub length, with potential implications for experimental control of persistent currents, as further illustrated by calculations of the net current.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
8 pages, 3 figures
Time Glasses: Symmetry Broken Chaotic Phase with a Finite Gap
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-06 20:00 EDT
We introduce the time glass, a non-periodic analogue of the discrete time crystal that arises in periodically driven dissipative quantum many-body systems. This phase is defined by two key features: (i) spatial long-range order arising from the spontaneous breaking of an internal symmetry, and (ii) temporally chaotic oscillations of the order parameter, whose lifetime diverges with system size. To characterize the time glass phase, we focus on the spectral gap of the one-cycle (Floquet) Liouvillian, which determines the decay rate of the slowest relaxation mode. Numerical studies of periodically driven dissipative Ising models show that, in the time glass phase, the Liouvillian gap remains finite in the thermodynamic limit, in contrast to time crystals where the gap closes exponentially with system size. We further demonstrate that the Liouvillian gap converges to the decay rate of the order-parameter autocorrelation derived from the classical (mean-field) dynamics in the thermodynamic limit. This result establishes a direct correspondence between microscopic spectral features and emergent macroscopic dynamics in driven dissipative quantum systems. At first glance, the existence of a nonzero Liouvillian gap appears incompatible with the presence of indefinitely persistent chaotic oscillations. We resolve this apparent paradox by showing that the quantum Rényi divergence between a localized coherent initial state and the highly delocalized steady state grows unboundedly with system size. This divergence allows long-lived transients to persist even in the presence of a finite Liouvillian gap.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
27 pages, 20 figures
Tip-induced nitrene generation
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Leonard-Alexander Lieske, Aaron H. Oechsle, Igor Rončević, Ilias Gazizullin, Florian Albrecht, Matthias Krinninger, Leonhard Grill, Friedrich Esch, Leo Gross
We generated trinitreno-s-heptazine, a small molecule featuring three nitrene centers, by tip-induced chemistry from the precursor 2,5,8-triazido-s-heptazine on bilayer NaCl on Au(111). The precursor’s azide groups were dissociated to form mono-, di- and trinitreno-s-heptazine, yielding molecules with one to three nitrene centers. The precursor and its products are characterized by atomic force microscopy and scanning tunnelling microscopy. Broken-symmetry DFT and configuration interaction calculations of inter- and intra-nitrene exchange couplings suggest a ferromagnetic coupling of the S = 1 nitrene centers, resulting in a high-spin septet ground state for neutral trinitreno-s-heptazine in the gas phase. On bilayer NaCl on Au(111), the combined results of experiments and theory suggest trinitreno-s-heptazine to be an anion with a sextet ground state.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Lattice Mismatch Driven In Plane Strain Engineering for Enhanced Upper Critical Fields in Mo2N Superconducting Thin Films
New Submission | Superconductivity (cond-mat.supr-con) | 2025-06-06 20:00 EDT
Aditya Singh, Divya Rawat, Victor Hjort, Abhisek Mishra, Arnaud le Febvrier, Subhankar Bedanta, Per Eklund, Ajay Soni
Transition metal nitrides are a fascinating class of hard coating material that provide an excellent platform for investigating superconductivity and fundamental electron phonon interactions. In this work the structural morphological and superconducting properties have been studied for Mo2N thin films deposited via direct current magnetron sputtering on cplane Al2O3 and MgO substrates to elucidate the effect of internal strain on superconducting properties. High resolution X Ray diffraction and time of flight elastic recoil detection analysis confirms the growth of single phase Mo2N thin films exhibiting epitaxial growth with twin domain structure. Low temperature electrical transport measurements reveal superconducting transitions at 5.2 K and 5.6 K with corresponding upper critical fields of 5 T and 7 T for the films deposited on Al2O3 and MgO, respectively. These results indicate strong type II superconductivity and the observed differences in superconducting properties are attributed to substrate induced strain which leads to higher e ph coupling for the film on MgO substrate. These findings highlight the tunability of superconducting properties in Mo2N films through strategic substrate selection.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
Revisiting cofactor conditions: Elimination of transition layers in compound domains
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Mohd Tahseen, Vivekanand Dabade
This paper investigates the conditions necessary for the elimination of transition layers at interfaces involving compound domains, extending the classical framework of cofactor conditions. Although cofactor conditions enable stress-free phase boundaries between Type I/II domains and austenite, their applicability to compound domains has remained limited. Here, we present a comprehensive theoretical framework to characterize all compatible interfaces, highlighting the fundamental importance of the commutation property among martensitic variants. By establishing necessary and sufficient algebraic conditions, referred to as extreme compatibility conditions, we demonstrate the simultaneous elimination of transition layers at phase interfaces for both Type I/II and compound laminates, across all volume fractions of the martensitic variants. We also investigate the possibility of achieving supercompatibility in non-conventional twins, recently observed in the NiMnGa system. The focus of our work is on cubic-to-orthorhombic and cubic-to-monoclinic~II phase transformations, for which the extreme compatibility conditions are explicitly derived and systematically analyzed. The theory predicts novel zero-elastic-energy microstructures, including an increased number of triple clusters, spearhead-shaped martensitic nuclei, stress-free inclusions of austenite within martensite, and distinctive four-fold martensitic clusters. This significantly expands the possible modes of forming stress-free interfaces between phases and reveals new energy-minimizing microstructures that can facilitate the nucleation of martensite within austenite and vice versa. These configurations highlight significant enhancements in transformation reversibility and material durability, guiding the rational design of next-generation shape memory alloys with optimized functional properties.
Materials Science (cond-mat.mtrl-sci)
Impact of border defects on the magnetic flux penetration in superconducting films
New Submission | Superconductivity (cond-mat.supr-con) | 2025-06-06 20:00 EDT
Alejandro V. Silhanek, Lu Jiang, Cun Xue, Benoît Vanderheyden
Defects in superconducting systems are ubiquitous and nearly unavoidable. They can vary in nature, geometry, and size, ranging from microscopic-size defects such as dislocations, grain boundaries, twin planes, and oxygen vacancies, to macroscopic-size defects such as segregations, indentations, contamination, cracks, or voids. Irrespective of their type, defects perturb the otherwise laminar flow of electric current, forcing it to deviate from its path. In the best-case scenario, the associated perturbation can be damped within a distance of the order of the size of the defect if the rigidity of the superconducting state, characterized by the creep exponent $ n$ , is low. In most cases, however, this perturbation spans macroscopic distances covering the entire superconducting sample and thus dramatically influences the response of the system. In this work, we review the current state of theoretical understanding and experimental evidence on the modification of magnetic flux patterns in superconductors by border defects, including the influence of their geometry, temperature, and applied magnetic field. We scrutinize and contrast the picture emerging from a continuous media standpoint, i.e. ignoring the granularity imposed by the vortex quantization, with that provided by a phenomenological approach dictated by the vortex dynamics. In addition, we discuss the influence of border indentations on the nucleation of thermomagnetic instabilities. Assessing the impact of surface and border defects is of utmost importance for all superconducting technologies, including superconducting resonators, superconducting single-photon detectors, superconducting radio-frequency cavities and accelerators, superconducting cables, superconducting metamaterials, superconducting diodes, and many others.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
36 pages, 24 figures, 281 references
Kondo effect under arbitrary spin-momentum locking
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
The Kondo effect originates from the spin exchange scattering of itinerant electrons with a localized magnetic impurity. Here, we consider generalization of Weyl-type electrons with their spin locked on a spherical Fermi surface in an arbitrary way and study how such spin-momentum locking affects the Kondo effect. After introducing a suitable model Hamiltonian, a simple formula for the Kondo temperature is derived with the second-order perturbation theory, which proves to depend only on the spin averaged over the Fermi surface. In particular, the Kondo temperature is unaffected as long as the average spin vanishes, but decreases as the average spin increases in its magnitude, and eventually vanishes when the spin is completely polarized on the Fermi surface, illuminating the role of spin-momentum locking in the Kondo effect.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
5 pages, 2 figures
Tunable spin-phonon polarons in a chiral molecular qubit framework
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
Aimei Zhou, Ruihao Bi, Zhenghan Zhang, Luming Yang, Xudong Tian, Denan Li, Mingshu Tan, Weibin Ni, Haozhou Sun, Jinkun Guo, Xinxing Zhao, Zhifu Shi, Wei Tong, Zhitao Zhang, Jin-Hu Dou, Feng Jin, Shi Liu, Mircea Dinca, Tijana Rajh, Jian Li, Wenjie Dou, Lei Sun
Chiral structures that produce asymmetric spin-phonon coupling can theoretically generate spin-phonon polarons – quasiparticles exhibiting non-degenerate spin states with phonon displacements. However, direct experimental evidence has been lacking. Using a chiral molecular qubit framework embedding stable semiquinone-like radicals, we report spin dynamic signatures that clearly indicate the formation of spin-phonon polarons for the first time. Our non-adiabatic model reveals that these quasiparticles introduce an active spin relaxation channel when polaron reorganization energy approaches Zeeman splitting. This new channel manifests as anomalous, temperature-independent spin relaxation, which can be suppressed by high magnetic fields or pore-filling solvents (e.g. CH2Cl2, CS2). Such field- and guest-tunable relaxation is unattainable in conventional spin systems. Harnessing this mechanism could boost repetition rates in spin-based quantum information technologies without compromising coherence.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Chemical Physics (physics.chem-ph), Quantum Physics (quant-ph)
17 pages, 5 figures
Strongly enhanced topological quantum phases in dual-surface AlO$_x$-encapsulated MnBi$_2$Te$_4$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Zichen Lian, Yongqian Wang, Yongchao Wang, Liangcai Xu, Jinsong Zhang, Chang Liu, Yayu Wang
The topological quantum phases in antiferromagnetic topological insulator MnBi$ _2$ Te$ _4$ hold promise for next-generation spintronics, but their experimental realization has been constrained by challenges in preparing high-quality devices. In this work, we report a new wax-assisted exfoliation and transfer method that enables the fabrication of MnBi$ _2$ Te$ _4$ heterostructures with both surfaces encapsulated by AlO$ _x$ . This strategy strongly enhances the topological quantum phases in MnBi$ _2$ Te$ _4$ flakes. We observe the robust axion insulator state in even-layer device with wide zero Hall plateau and high longitudinal resistivity, and the quantum anomalous Hall effect in odd-layer device with large hysteresis and sharp plateau transition. These results demonstrate that the combination of wax exfoliation and AlO$ _x$ encapsulation provides great potentials for exploring novel topological quantum phenomena and potential applications in MnBi$ _2$ Te$ _4$ and other two-dimensional materials.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Dynamics of Wound Closure in Living Nematic Epithelia
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-06 20:00 EDT
Henry Andralojc, Jake Turley, Helen Weavers, Paul Martin, Isaac V. Chenchiah, Rachel R. Bennett, Tanniemola B. Liverpool
We study theoretically the closure of a wound in a layer of epithelial cells in a living tissue after damage. Our analysis is informed by our recent experiments observing re-epithelialisation in vivo of Drosophila pupae. On time and length-scales such that the evolution of the epithelial tissue near the wound is well captured by that of a 2D active fluid with local nematic order, we consider the free-surface problem of a hole in a bounded region of tissue, and study the role that active stresses far from the hole play in the closure of the hole. For parallel anchored nematic order at the wound boundary (as we observe in our experiments), we find that closure is accelerated when the active stresses are contractile and slowed down when the stresses are extensile. Parallel anchoring also leads to the appearance of topological defects which annihilate upon wound closure.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
16 pages, 7 figures
Identification of the high-pressure phases of alpha-SnWO4 combining x-ray diffraction and crystal structure prediction
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Daniel Diaz-Anichtchenko, Jordi Ibáñez, Pablo Botella, Robert Oliva, Alexei Kuzmin, Li Wang, Yuwei Li, Alfonso Muñoz, Frederico Alabarse, Daniel Errandonea
We have characterized the high-pressure behavior of alpha-SnWO4. The compound has been studied up to 30 GPa using a diamond-anvil cell and synchrotron powder X-ray diffraction. We report evidence of two structural phase transitions in the pressure range covered in our study, and we propose a crystal structure for the two high-pressure phases. The first one, observed around 12.9 GPa, has been obtained combining indexation using DICVOL and density-functional theory calculations. The second high-pressure phase, observed around 17.5 GPa, has been determined by using the CALYPSO code, the prediction of which was supported by a Le Bail fit to the experimental X-ray diffraction patterns. The proposed structural sequence involves two successive collapses of the unit-cell volume and an increase in the coordination number of Sn and W atoms. The room-temperature equations of state, the principal axes of compression and their compressibility, the elastic constants, and the elastic moduli are reported for {\alpha}-SnWO4 and for the two high-pressure phases.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other)
20 pages, 8 figures, 7 tables
Physica B 696, 416666 (2025)
Ultrafast generation of coherent soft-shear phonons in halide perovskites via anisotropic photostriction
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Dmytro Horiachyi (1), Mikhail O. Nestoklon (1), Ilya A. Akimov (1), Artur V. Trifonov (1), Nikita V. Siverin (1), Nataliia E. Kopteva (1), Alexander N. Kosarev (1), Dmitri R. Yakovlev (1), Vitalyi E. Gusev (2), Melina Fries (3), Olga Trukhina (3), Vladimir Dyakonov (3), Manfred Bayer (1 and 4) ((1) Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany (2) Laboratoire d’Acoustique de l’Université du Mans (LAUM), UMR CNRS 6613, Institut d’Acoustique-Graduate School (IA-GS), Le Mans Université, Le Mans, France (3) Experimental Physics 6 and Würzburg-Dresden Cluster of Excellence <a href=”http://ct.qmat“ rel=”external noopener nofollow” class=”link-external link-http”>this http URL</a>, Julius-Maximilians-Universität Würzburg, 97070 Würzburg, Germany (4) Research Center Future Energy Materials and Systems, Technische Universität Dortmund, 44227 Dortmund, Germany)
Optical generation of transverse coherent phonons by femtosecond light pulses is appealing for high-speed sub-THz active control of material properties. Lead-free double perovskite semiconductors, such as Cs2AgBiBr6, attract particular interest due to their cubic to tetragonal phase transition below room temperature and strong polaron effects from carrier-lattice coupling. Here, we reveal that the anisotropic photostriction in halide perovskites with tetragonal crystal structure represents an efficient non-thermal tool for generating transverse coherent phonons. In particular, we demonstrate that along with compressive strain, optical generation of photoexcited carriers leads to strong shear strain in Cs2AgBiBr6 below the phase transition temperature of 122 K. Using time-domain Brillouin spectroscopy, we observe coherent transverse and longitudinal acoustic phonons with comparable amplitudes in the tetragonal phase, while in the cubic phase only longitudinal phonons are generated. The polarization of the photoinduced transverse phonons is dictated by the projection of the c-axis on the surface plane, which leads to a prominent anisotropic polarization response in the detection. The generated strain pulses correspond to transverse acoustic soft eigenmodes with a strong temperature dependence of dispersion, which provides an additional degree of freedom for active hypersonic control.
Materials Science (cond-mat.mtrl-sci)
Opposite pressure effects on magnetic phase transitions in NiBr2
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Parvez Ahmed Qureshi, Krishna Kumar Pokhrel, Jiri Prchal, Subhasmita Ray, Sergiu Arapan, Karel Carva, Vladimir Sechovsky, Jiri Pospisil
NiBr2, similar to NiI2, exhibits the onset of collinear antiferromagnetism at a subroom temperature and, with further cooling, undergoes a transition to a helimagnetic ordering associated with multiferroic behavior. This work investigates the hydrostatic pressure effects on magnetic phase transitions in NiBr2. We measured isobaric temperature dependencies of AC magnetic susceptibility at various pressures up to 3 GPa. The experimental data are interpreted in conjunction with the results of theoretical calculations focused on pressure influence on the hierarchy of exchange interactions. Contrary to the NiI2 case, the phase transition to helimagnetism rapidly shifts to lower temperatures with increasing pressure. Similar to the NiI2, the Neel temperature increases with pressure. The rate of increase accelerates when the helimagnetic phase is suppressed by pressure. The ab initio calculations link these contrasting trends to pressure-enhanced magnetic exchange interactions. Similarly to the NiI2 case, the stabilization of the collinear AFM phase is driven primarily by the second-nearest interlayer coupling (j2’). Furthermore, the ratio of in-plane interactions makes helimagnetic order in NiBr2 much more volatile, which permits its suppression with already small pressures. These findings highlight the principal role of interlayer interactions in the distinct response of NiBr2 and NiI2 magnetic phases to external pressure.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Pressure-Induced Decomposition of beta-SnWO4
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Sergio Ferrari, Daniel Diaz-Anichtchenko, Pablo Botella, Jordi Ibáñez, Robert Oliva, Alexei Kuzmin, Alfonso Muñoz, Frederico Alabarse, Daniel Errandonea
This study reports the decomposition of beta-SnWO4 into Sn, SnO2, and WO3 induced by static compression. We performed high-pressure synchrotron powder angle-dispersive X-ray diffraction measurements and found that decomposition occurs at a pressure of 13.97(5) GPa and is irreversible. This result contradicts a previous study that, based on density-functional theory calculations and crystal-chemistry arguments, predicted a pressure-driven transition from beta-SnWO4 to alpha-SnWO4. Our analysis indicates that the observed decomposition is unrelated to mechanical or dynamic instabilities. Instead, it likely stems from frustration of the beta-alpha transition, as this transformation requires a change in Sn coordination from octahedral to tetrahedral. The assessment of how pressure influences the volume of the unit cell provided an accurate determination of the room-temperature pressure-volume equation of state for beta-SnWO4. Furthermore, the elastic constants and moduli, as well as the pressure dependence of Raman and infrared modes of beta-SnWO4, were derived from density-functional theory calculations. Several phonon modes exhibited softening, and three cases of phonon anti-crossing were observed.
Materials Science (cond-mat.mtrl-sci)
26 pages, 9 figures, 4 tables
Results in Physics 74, 108304 (2025)
Gate-tunable spectrum and charge dispersion mitigation in a graphene superconducting qubit
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
Nicolas Aparicio, Simon Messelot, Edgar Bonet-Orozco, Eric Eyraud, Kenji Watanabe, Takashi Taniguchi, Johann Coraux, Julien Renard
Controlling the energy spectrum of quantum-coherent superconducting circuits, i.e. the energies of excited states, the circuit anharmonicity and the states’ charge dispersion, is essential for designing performant qubits. This control is usually achieved by adjusting the circuit’s geometry. In-situ control is traditionally obtained via an external magnetic field, in the case of tunnel Josephson junctions. More recently, semiconductor-weak-links-based Josephson junctions have emerged as an alternative building block with the advantage of tunability via the electric-field effect. Gate-tunable Josephson junctions have been succesfully integrated in superconducting circuits using for instance semiconducting nanowires or two-dimensional electron gases. In this work we demonstrate, in a graphene superconducting circuit, a large gate-tunability of qubit properties: frequency, anharmonicity and charge dispersion. We rationalize these features using a model considering the transmission of Cooper pairs through Andreev bound states. Noticeably, we show that the high transmission of Cooper pairs in such weak link strongly suppresses the charge dispersion. Our work illustrates the potential for graphene-based qubits as versatile building-blocks in advanced quantum circuits.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Field-controlled Electronic Breathing Modes and Transport in Nanoporous Graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
Nanoporous graphene (NPG) has been fabricated by on-surface-self assembly in the form of arrays of apporx. 1 nm-wide graphene nanoribbons connected via molecular bridges in a two-dimensional crystal lattice. It is predicted that NPG may, despite its molecular structure, work as electron waveguides that display e.g. Talbot wave interference. Here, we demonstrate how the electronic wave guidance may be controlled by the use of electrical fields transverse to the ribbons; at low fields, point injected currents display spatially periodic patterns along the ribbons, while high fields localize the injected current to single ribbons. This behavior constitutes an electronic version of optical breathing modes of Bloch oscillations, providing a simple mechanism for controlling the current patterns down to the molecular scale. The robustness of the self-repeating patterns under disorder demonstrate that the breathing modes of single-ribbon injections offer exciting opportunities for applications in nanoelectronics, molecular sensing, and quantum information processing.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Hole spin qubits in unstrained Germanium layers
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
Lorenzo Mauro, Mauricio J. Rodriguez, Esteban A. Rodriguez-Mena, Yann-Michel Niquet
Strained germanium heterostructures are one of the most promising material for hole spin qubits but suffer from the strong anisotropy of the gyromagnetic factors that hinders the optimization of the magnetic field orientation. The figures of merit (Rabi frequencies, lifetimes…) can indeed vary by an order of magnitude within a few degrees around the heterostructure plane. We propose to address this issue by confining the holes at the interface of an unstrained, bulk Ge substrate or thick buffer. We model such structures and show that the gyromagnetic anisotropy is indeed considerably reduced. In addition, the Rabi frequencies and quality factors can be significantly improved with respect to strained heterostructures. This extends the operational range of the qubits and shall ease the scale-up to many-qubit systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Engineering harmonic emission through spatial modulation in a Kitaev chain
New Submission | Other Condensed Matter (cond-mat.other) | 2025-06-06 20:00 EDT
Nivash R., S. Srinidhi, Jayendra N. Bandyopadhyay, Amol R. Holkundkar
We investigate High-harmonic generation (HHG) in a dimerized Kitaev chain. The dimerization in the model is introduced through a site-dependent modulating potential, determined by a parameter $ \lambda \in [-1:1]$ . This parameter also determines the strength of the hopping amplitudes and tunes the system’s topology. Depending upon the parameter $ \lambda$ , the HHG emission spectrum can be classified into three segments. The first segment exhibits two plateau structures, with the dominant one resulting from transitions to the chiral partner state, consistent with quasiparticle behavior in the topological superconducting phase. The second segment displays multiple plateaus, where intermediate states enable various transition pathways to higher conduction bands. Finally, the third segment presents broader plateaus, indicative of active interband transitions. In the $ \lambda\leq0$ regime, we observe the mid-gap states (MGSs) hybridize with the bulk, suppressing the earlier observed harmonic enhancements. This highlights the key role of the intermediate states, particularly when MGSs are isolated. These results demonstrate that harmonic emission profiles can be selectively controlled through the modulating parameter $ \lambda$ , offering new prospects for tailoring HHG in topological systems.
Other Condensed Matter (cond-mat.other), Superconductivity (cond-mat.supr-con), Atomic Physics (physics.atom-ph), Quantum Physics (quant-ph)
10 pages, 4 figures
Mechanistic Insights into Water-Splitting, Proton Migration, and Hydrogen Evolution Reaction in g-C3N4/TiO2-B and Li-F co-doped Heterostructures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Shuhan Tang, Qi Jiang, Shuang Qiu, Hanyang Ji, Xiaojie Liu
Solar water splitting has received a lot of attention due to its high efficiency and clean energy production potential. Herein, based on the band alignment principle, the g-C3N4/TiO2-B(001) heterostructure is strategically designed, then a Li-F co-doping approach is developed and implemented, leading to significant enhancement in the photocatalytic hydrogen evolution efficiency of the heterostructure systems. The decomposition of water molecule on the surface of heterostructures, the migration and diffusion of proton across the interface, and the hydrogen evolution performance are systematically studied and comprehensively analyzed. The results demonstrate that the heterojunction surface exhibits a relatively low energy barrier for water decomposition, facilitating both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Proton transfer preferentially occurs from the TiO2-B(001) surface to the g-C3N4 surface through the interface. The presence of polar covalent bonds establishes a substantial energy barrier for proton migration from TiO2-B(001) surface to the interface, representing a rate-determining factor in the hydrogen evolution process. The formation of hydrogen bonds significantly reduces the migration energy barrier for protons crossing the interface to the g-C3N4 surface. Hydrogen adsorption free energy analysis show that that the heterojunction surface exhibits optimal proton adsorption and desorption characteristics. The synergistic combination of low water decomposition energy barrier, reduced proton migration energy barriers and exceptional HER performance endows both g-C3N4/TiO2-B(001) heterostructure and Li-F co-doped g-C3N4/TiO2-B(001) heterojunction with remarkbale potential as efficient HER photocatalyst.
Materials Science (cond-mat.mtrl-sci)
Magnetic Dissipation in Ferrofluids
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Lili Vajtai, Norbert Marcel Nemes, Maria del Puerto Morales, Bence Gábor Márkus, László Forró, Ferenc Simon
Ferrofluids, composed of magnetic nanoparticles suspended in a non-magnetic carrier liquid, have attracted considerable attention since their discovery in the 1960s. Their combination of liquid and magnetic properties gives rise to complex behaviors and unique functionalities, enabling a wide range of technological applications. Among these is the ability of the magnetic material to be moved by and to absorb heat when exposed to an external magnetic field – a process that can occur through various dissipation mechanisms depending on the system. A detailed understanding of these mechanisms is crucial for tailoring materials to specific applications. We provide a comprehensive overview of the theoretical principles underlying different energy dissipation processes and propose a coherent framework for their interpretation. Particular attention is devoted to describing the frequency-dependent susceptibility, which is the key parameter to describe dissipation. We demonstrate that dissipation, predicted from magnetometry-based studies, matches well with direct, frequency-dependent calorimetric results, expanding the available frequency range of the characterization. The demonstrating measurements were carried out with a dilute ferrofluid containing magnetite nanoparticles of a mean diameter of 10.6 nm.
Materials Science (cond-mat.mtrl-sci)
13 pages, 8 figures
Complexity reduction of physical models: an equation-free approach by means of scaling
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-06 20:00 EDT
Simone Rusconi, Christina Schenk, Razvan Ceuca, Arghir Zarnescu, Elena Akhmatskaya
The description of complex physical phenomena often involves sophisticated models that rely on a large number of parameters, with many dimensions and scales. One practical way to simplify that kind of models is to discard some of the parameters, or terms of underlying equations, thus giving rise to reduced models. Here, we propose a general approach to obtaining such reduced models. The method is independent of the model in use, i.e., equation-free, depends only on the interplay between the scales and dimensions involved in the description of the phenomena, and controls over-parametrization. It also quantifies conditions for asymptotic models by providing explicitly computable thresholds on values of parameters that allow for reducing complexity of a model, while preserving essential predictive properties. Although our focus is on complexity reduction, this approach may also help with calibration by mitigating the risks of over-parameterization and instability in parameter estimation. The benefits of this approach are discussed in the context of the classical projectile model.
Soft Condensed Matter (cond-mat.soft)
Hybrid between biologically inspired and quantum inspired many-body states
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-06 20:00 EDT
Deep neural networks can represent very different sorts of functions, including complex quantum many-body states. Tensor networks can also represent these states, have more structure and are easier to optimize. However, they can be prohibitively costly computationally in two or higher dimensions. Here, we propose a generalization of the perceptron - the perceptrain - which borrows features from the two different formalisms. We construct variational many-body ansatz from a simple network of perceptrains. The network can be thought of as a neural network with a few distinct features inherited from tensor networks. These include efficient local optimization akin to the density matrix renormalization algorithm, instead of optimizing of all the parameters at once; the possibility to dynamically increase the number of parameters during the optimization; the possibility to compress the state to avoid overfitting; and a structure that remains quantum-inspired. We showcase the ansatz using a combination of Variational Monte-Carlo (VMC) and Green Function Monte-Carlo (GFMC) on a $ 10\times 10$ transverse field quantum Ising model with a long range $ 1/r^6$ antiferromagnetic interaction. The model corresponds to the Rydberg (cold) atoms platform proposed for quantum annealing. We consistently find a very high relative accuracy for the ground state energy, around $ 10^{-5}$ for VMC and $ 10^{-6}$ for GFMC in all regimes of parameters, including in the vicinity of the quantum phase transition. We used very small ranks ($ \sim 2-5$ ) of perceptrains, as opposed to multiples of thousand used in matrix product states. The optimization of the energy was robust with respect to the choice of initial conditions and hyper-parameters, in contrast to a common experience when using neural network wave functions.
Strongly Correlated Electrons (cond-mat.str-el), Disordered Systems and Neural Networks (cond-mat.dis-nn), Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
16 pages, 18 figures, 1 table
Strongly Correlated Transport in Topological Y-Junction Devices
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
I study electron transport through a Y-shaped junction of helical edge states in a two-dimensional topological insulator (2DTI), focusing on the strongly interacting regime. An experimentally accessible device geometry is proposed, and the corresponding conductance tensor is calculated. These results position Y-junctions of 2DTI as promising platforms for interaction-driven transport and nanoscale device applications in spintronics and topological electronics.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
15 pages, 9 figures
Chirality Amplification and Deracemization in Liquid Crystals
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-06 20:00 EDT
Matthew J. Deutsch, Robin L. B. Selinger, Paul van der Schoot
Liquid crystal mesophases of achiral molecules are normally achiral, yet in a few materials they spontaneously deracemize and form right- and left-handed chiral domains. One mechanism that drives deracemization is molecular shape fluctuations between axial chiral conformations, where molecular interactions favor matching chirality and promote helical twist. Cooperative chiral ordering may also play a role in chirality amplification, as when a tiny fraction of chiral dopant drives a nematic phase to become cholesteric. We present a model of cooperative chiral ordering in liquid crystals using Maier-Saupe theory, and predict a phase diagram with a deracemized cholesteric phase as well as racemic nematic and isotropic phases. Our model also predicts chirality amplification in the nematic phase, which may be observed even in materials where the deracemization transition is preempted by a transition to another phase. We compare these results with Monte Carlo simulation studies of the switchable chiral Lebwohl-Lasher model, where each spin switches between right- and left-handed chiral states. Simulation results validate the predicted phase diagram, demonstrate chiral amplification in the racemic nematic phase, and reveal coarsening dynamics in the deracemized phase. Our results suggest that cooperative chiral ordering via molecular shape transitions is a common mechanism in liquid crystals.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
17 pages, 10 figures
How does picosecond structural deformation of (Ba,Sr)TiO$_{3}$ relate to the pyroelectric effect?
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
D. Schmidt, J. Wawra, D. Hensel, M.Brede, R. Hühne, P. Gaal
The pyroelectric effect in ferroelectric thin films is typically composed of different contributions, which are difficult to disentangle. In addition, clamping to the substrate interface plays an important role. We studied epitaxial (Ba,Sr)TiO$ _3$ thin films grown on NdScO$ _3$ to see if time-resolved measurements can shed more light on the complex interaction. In particular, we compare standard measurements of the pyroelectric coefficient by temperature-dependent hysteresis loops to transient deformation measurements on picosecond timescales in the same material. The advantage of the time-resolved approach lies in its increased sensitivity in thin films compared to that of polarization hysteresis measurements. Whereas a fast thermal expansion of the ferroelectric thin film was observed after femtosecond laser excitation of the intermediate SrRuO$ _3$ layer, heat diffusion simulations reveal frustration of the thermal expansion, which might be explained with the charge dynamics at the Schottky barrier formed at the SrRuO$ _3$ /(Ba,Sr)TiO$ _3$ . More studies are required to quantitatively assess the individual contributions to the pyroelectric coefficient of the materials used in our layer architecture.
Materials Science (cond-mat.mtrl-sci)
7 pages and supplemental material
Ultrafast magneto-lattice dynamics in two-dimensional CrSBr driven by terahertz excitation
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Yiqi Huo, Shuo Li, Luo Yan, Ningbo Li, Sergei Tretiak, Liujiang Zhou
Terahertz (THz) lasers provide a new research perspective for spin electronics applications due to their sub-picosecond time resolution and non-thermal ultrafast demagnetization, but the interaction between spin, charge and lattice dynamics remains unclear. This study investigates photoinduced ultrafast demagnetization in monolayer CrSBr, a two-dimensional material with strong spin-orbit and spin-lattice coupling, and resolves its demagnetization process. Two key stages are identified: the first, occurring within 20 fs, is characterized by rapid electron-driven demagnetization, where charge transfer and THz laser are strongly coupled. In the second stage, light-induced lattice vibrations coupled to spin dynamics lead to significant spin changes, with electron-phonon coupling playing a key role. Importantly, the role of various phonon vibration modes in the electron relaxation process was clearly determined, pointing out that the electronic relaxation of the B3g1 phonon vibration mode occurs within 83 fs, which is less than the commonly believed 100 fs. Moreover, the influence of this coherent phonon on the demagnetization change is as high as 215 %. These insights into multiscale magneto-structural coupling advance the understanding of nonequilibrium spin dynamics and provide guidelines for the design of light-controlled quantum devices, particularly in layered heterostructures for spintronics and quantum information technologies.
Materials Science (cond-mat.mtrl-sci)
Estimation of Exciton Binding Energy and lifetime for Mono-layer Transition Metal Dichalcogenides
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
Rohit Ramesh Nimje, Swati G, Ashutosh Mahajan
In this work, we present a mathematical model for the Wannier-Mott exciton in monolayers of transition metal dichalcogenides such as $ WS_2$ , $ WSe_2$ , $ MoS_2$ , $ MoSe_2$ that estimates the radiation lifetime in the effective mass approximation. We calculate exciton energy, and binding energy by solving the Schrodinger wave equation with open boundary conditions to obtain quasi-bound states in the confined direction in the monolayer and decay rates by the Fermi-Golden rule. The proposed model uses only the physical parameters such as band offsets, effective mass, and dielectric constants for the monolayers of $ WS_2$ , $ WSe_2$ , $ MoS_2$ , and $ MoSe_2$ . The model is validated against III-V material quantum well heterostructure, and the estimated effective lifetime considering the thermalization of the exciton has been compared with photoluminescence decay for the TMD heterostructure. Our calculated values show good agreement with the time-resolved photoluminescence spectroscopy measurements and DFT estimations.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
8 pages, 9 figures
Optimal protocol for collisional Brownian engines
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-06 20:00 EDT
Collisional Brownian engines have recently gained attention as alternatives to conventional nanoscale engines. However, a comprehensive optimization of their performance, which could serve as a benchmark for future engine designs, is still lacking. In this work, we address this gap by deriving and analyzing the optimal driving protocol for a collisional Brownian engine. By maximizing the average output work, we show that the optimal protocol consists of linear force segments separated by impulsive delta-like kicks that instantaneously reverse the particle’s velocity. This structure enforces constant velocity within each stroke, enabling fully analytical expressions for optimal output power, efficiency, and entropy production. We demonstrate that the optimal protocol significantly outperforms standard strategies (such as constant, linear, or periodic drivings) achieving higher performance while keeping entropy production under control. Remarkably, when evaluated using realistic experimental parameters, the efficiency approaches near-unity at the power optimum, with entropy production remaining well controlled, a striking feature of the optimal protocol. To analyze a more realistic scenario, we examine the impact of smoothing the delta-like forces by introducing a finite duration and find that, although this reduces efficiency and increases entropy production, the optimal protocol still delivers high power output in a robust manner. Altogether, our results provide a theoretical benchmark for finite-time thermodynamic optimization of Brownian engines under time-periodic drivings.
Statistical Mechanics (cond-mat.stat-mech)
10 pages, 4 figures
Collective excitation spectra of dipolar bosonic fractional quantum Hall states
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-06-06 20:00 EDT
Moumita Indra, Pankaj Kumar Mishra
We numerically investigate the collective excitation of spin-conserving and spin-reversed configuration of rotating diluted ultra-cold dipolar Bose gas. Rotating trapped Bose gas produces a fictitious magnetic field perpendicular to the trapping harmonic potential, which exhibits strongly correlated fractional quantum Hall states. We consider the long-range dipole-dipole interaction and compute the low lying excitations spectrum for the three fractions of the first Jain series $ \nu = 1/2, 1/4, 1/6$ . We find that for both the spin-conserving and spin-reversed excitation the gap between the fundamental mode and the higher excitation mode increases upon increase in the filling fraction. The fundamental modes and the next higher-energy mode of excitation spectra for each of the three fractions show the presence of double roton for spin-conserving configuration only. Finally we complement our observation by calculating the spectral weight for the fundamental mode of excitation spectra which show the momenta at which the spectral weight exhibits the maxima shifts towards the lower momenta for both the excitations. Our observation for the spectral weight could be related with the inelastic Raman scattering which may be useful for the future experimental study to detect the excitation in ultracold system.
Quantum Gases (cond-mat.quant-gas)
10pages, 5 figures
Bilayer triple-Q state driven by interlayer higher-order exchange interactions
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Bjarne Beyer, Mara Gutzeit, Tim Drevelow, Isabel Schwermer, Soumyajyoti Haldar, Stefan Heinze
Using first-principles calculations and an atomistic spin model we predict the stabilization of a bilayer triple-Q state in an atomic Mn bilayer on Ir(111) due to interlayer higher-order exchange interactions. Based on density functional theory (DFT) we study the magnetic interactions and ground state in a Mn monolayer and bilayer on the Ir(111) surface. We calculate the energy dispersion of spin spirals (single-Q states) to scan a large part of the magnetic phase space and to obtain constants of pair-wise exchange interactions. By including spin-orbit coupling we determine the strength of the Dzyaloshinskii-Moriya interaction. To reveal the role of higher-order exchange interactions in these films, we consider multi-Q states obtained by a superposition of spin spirals. For the Mn monolayer in fcc stacking on Ir(111), the triple-Q state exhibits the lowest total energy in DFT, while the Néel state is most favorable for hcp stacking. For the Mn bilayer on Ir(111), two types of the triple-Q state are possible. In both magnetic configurations, a triple-Q state occurs within each of the Mn layers. However, only in one of them the spin alignment between the layers is such that nearest-neighbor spins of different layers also exhibit the tetrahedron angles which characterize the triple-Q state. We denote this state – which has the lowest total energy in our DFT calculations – as the ideal bilayer triple-Q state. This state exhibits significant topological orbital moments within each of the two Mn layers which are aligned in parallel resulting in a large topological orbital magnetization. We interpret the DFT results within an atomistic spin model which includes pair-wise Heisenberg exchange, the Dzyaloshinskii-Moriya interaction, as well as higher-order exchange interactions….
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Frustrated $J_1-J_2$ Diamond Lattice Antiferromagnet Co$_2$Ti$_3$O$_8$ with a Vacancy-ordered Spinel Structure Synthesized via a Topochemical Reaction
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-06 20:00 EDT
Rio Kumeda, Yuya Haraguchi, Daisuke Nishio-Hamane, Akira Matsuo, Koichi Kindo, Hiroko Aruga Katori
Metastable Co$ _2$ Ti$ _3$ O$ _8$ was synthesized through a topochemical reaction using Li$ _2$ CoTi$ _3$ O$ _8$ as the precursor, resulting in a vacancy-ordered spinel structure. Crystal structure analysis confirmed that Co ions selectively occupy the A-site, giving rise to a frustrated diamond lattice. Magnetic susceptibility and heat capacity measurements revealed antiferromagnetic order at 4.4 K, which is markedly suppressed compared to the negative Weiss temperature of $ {\sim}-27$ K, indicating a high degree of frustration effects. Pulsed high-field magnetization measurements revealed a four-step successive magnetic phase transition, demonstrating that Co$ _2$ Ti$ _3$ O$ _8$ is a promising candidate for a frustrated $ J_1-J_2$ diamond lattice. Additionally, the $ J_2/J_1$ ration estimated from the molecular field approximation suggests the possibility of a spiral ordered ground state. These observations highlight the potential of frustrated magnetism in ordered spinel structures to expand the material search space for quantum magnetism, including magnetic skyrmions.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
11 pages, 8 figures, accepted in Journal of the Physical Society of Japan
Classification and enumeration of solid-solid phase transition mechanisms
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Fang-Cheng Wang, Qi-Jun Ye, Yu-Cheng Zhu, Xin-Zheng Li
Crystal-structure match (CSM), the atom-to-atom correspondence between two crystalline phases, is used extensively to describe solid-solid phase transition (SSPT) mechanisms. However, existing computational methods cannot account for all possible CSMs. Here, we propose a formalism to classify all CSMs into a tree structure, which is independent of the choices of unit cell and supercell. We rigorously proved that only a finite number of noncongruent CSMs are of practical interest. By representing CSMs as integer matrices, we introduce the crystmatch method to exhaustively enumerate them, which uncontroversially solves the CSM optimization problem under any geometric criterion. For most SSPTs, crystmatch can reproduce all known deformation mechanisms and CSMs within 10 CPU minutes, while also revealing thousands of new candidates. The resulting database can be further used for comparing experimental phenomena, high-throughput energy barrier calculations, or machine learning.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
22 pages, 14 figures
Pressure-Driven Metallicity in Ångström-Thickness 2D Bismuth and Layer-Selective Ohmic Contact to MoS2
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Shuhua Wang, Shibo Fang, Qiang Li, Yunliang Yue, Zongmeng Yang, Xiaotian Sun, Jing Lu, Chit Siong Lau, L. K. Ang, Lain-Jong Li, Yee Sin Ang
Recent fabrication of two-dimensional (2D) metallic bismuth (Bi) via van der Waals (vdW) squeezing method opens a new avenue to ultrascaling metallic materials into the ångström-thickness regime [Nature 639, 354 (2025)]. However, freestanding 2D Bi is typically known to exhibit a semiconducting phase [Nature 617, 67 (2023), Phys. Rev. Lett. 131, 236801 (2023)], which contradicts with the experimentally observed metallicity in vdW-squeezed 2D Bi. Here we show that such discrepancy originates from the pressure-induced buckled-to-flat structural transition in 2D Bi, which changes the electronic structure from semiconducting to metallic phases. Based on the experimentally fabricated MoS2-Bi-MoS2 trilayer heterostructure, we demonstrate the concept of layer-selective Ohmic contact in which one MoS2 layer forms Ohmic contact to the sandwiched Bi monolayer while the opposite MoS2 layer exhibits a Schottky barrier. The Ohmic contact can be switched between the two sandwiching MoS2 monolayers by changing the polarity of an external gate field, thus enabling charge to be spatially injected into different MoS2 layers. The layer-selective Ohmic contact proposed here represents a layertronic generalization of metal/semiconductor contact, paving a way towards layertronic device application.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
14 pages, 5 figures
A framework for fluctuating times and counting observables in stochastic excursions
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-06 20:00 EDT
Guilherme Fiusa, Pedro E. Harunari, Abhaya S. Hegde, Gabriel T. Landi
Many natural systems exhibit dynamics characterized by alternating phases. Describing the fluctuations of such systems over stochastic trajectories is necessary across diverse fields, from biological motors to quantum thermal machines. In an accompanying Letter, we introduced the notion of stochastic excursions – a framework to analyze far from equilibrium processes via sub-trajectories. Through counting observables, this framework captures finite-time fluctuations and trajectory-level behavior, which provides insights into thermodynamical trade-offs between thermodynamic quantities of interest, such as entropy production and dynamical activity. In this work, we enhance this formalism by providing a suite of technical results on how to efficiently compute excursion-related quantities. Our analytical results provide explicit formulas for general moments of counting variables and excursion duration, as well as their covariance and conditional moments. We show that excursion statistics recover full counting statistics results, and uncover a relation between fluctuations of counting observables at single-excursion level and the steady state diffusion coefficient (noise). We also discuss a fluctuation theorem for individual excursions. In addition, we explore how analyzing excursions and using the results developed here can yield insights into three problems of interest: the three-qubit absorption refrigerator, cellular sensing, and birth-and-death processes.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
Companion paper to arXiv:2505.06208
Delicate Wannier insulators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
Zoltán Guba, Aris Alexandradinata, Tomáš Bzdušek
The defining feature of topological insulators is that their valence states are not continuously deformable to a suitably defined atomic limit without breaking the symmetry or closing the energy gap. When the atomic limit is given by symmetric exponentially-localized Wannier orbitals, one finds stable and fragile topological insulators characterized by robust bulk-boundary correspondence. More recently, delicate topological insulators (DIs) have been introduced, whose metallic states are guaranteed only at sharply terminated edges and surfaces. Although Wannierizable, their Wannier orbitals necessarily span multiple unit cells, thus refining the notion of the atomic limit. In this work, we extend delicate topological invariants from Bloch states to hybrid Wannier functions. The resulting models, dubbed delicate Wannier insulators (DWIs), are deformable to unicellular atomic limit in the absence of edges and surfaces; nevertheless, they exhibit obstructions to such deformations as well as topological boundary states in the presence of sharply terminated hinges and corners. We present a layering construction that allows us to elevate a DI in $ d$ dimensions into a DWI in $ (d,{+},1)$ dimensions. We illustrate the phenomenology of DWIs by deploying the layering construction on three concrete models.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
20 pages (including 11 figures, 1 table, and bibliography)
Designer polyradical nanographenes with strong spin entanglement and perturbation resilience via Clar’s goblet extension
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
En Li, Manish Kumar, Xinnan Peng, Tong Shen, Diego Soler-Polo, Yu Wang, Yu Teng, Haoyu Zhang, Shaotang Song, Jishan Wu, Pavel Jelinek, Jiong Lu
Polyradical nanographenes featuring strong spin entanglement and robust many-body spin states against external magnetic perturbations not only enable the exploration of correlated quantum magnetism at the molecular scale, but also constitute promising candidates for developing molecular qubits with chemical tunability and building scalable quantum networks. Here, we employed a predictive design strategy to achieve the on-surface synthesis of two homologues of Clar goblet, C62H22 and C76H26, via lateral and vertical extensions of the parent structure, respectively. Vertical extension increases the number of topologically frustrated zero-energy modes, which scale linearly with the total number of benzene ring rows. In contrast, the lateral extension enhances electron-electron interactions, leading to the emergence of additional radical states beyond those predicted by the topological zero-energy modes. Consequently, both structures exhibit correlated tetraradical character and a many-body singlet ground state as confirmed by multireference theoretical calculations. These magnetic states arise from unique magnetic origins and also display distinct resilience to external perturbations, which can be experimentally validated using nickelocene-functionalized scanning probe techniques. Our work presents a general strategy for rational design of highly entangled polyradical nanographenes with tunable spin numbers and resilience of their many-body spin states to perturbations, opening exciting possibilities for exploring novel correlated spin phases in molecular systems and advancing quantum information technologies.
Materials Science (cond-mat.mtrl-sci)
Overlap Gap and Computational Thresholds in the Square Wave Perceptron
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-06-06 20:00 EDT
Marco Benedetti, Andrej Bogdanov, Enrico M. Malatesta, Marc Mézard, Gianmarco Perrupato, Alon Rosen, Nikolaj I. Schwartzbach, Riccardo Zecchina
Square Wave Perceptrons (SWPs) form a class of neural network models with oscillating activation function that exhibit intriguing ``hardness’’ properties in the high-dimensional limit at a fixed signal-to-noise ratio $ \alpha = O(1)$ . In this work, we examine two key aspects of these models. The first is related to the so-called overlap-gap property, that is a disconnectivity feature of the geometry of the solution space of combinatorial optimization problems proven to cause the failure of a large family of solvers, and conjectured to be a symptom of algorithmic hardness. We identify, both in the storage and in the teacher-student settings, the emergence of an overlap gap at a threshold $ \alpha_{\mathrm{OGP}}(\delta)$ , which can be made arbitrarily small by suitably increasing the frequency of oscillations $ 1/\delta$ of the activation. This suggests that in this small-$ \delta$ regime, typical instances of the problem are hard to solve even for small values of $ \alpha$ . Second, in the teacher-student setup, we show that the recovery threshold of the planted signal for message-passing algorithms can be made arbitrarily large by reducing $ \delta$ . These properties make SWPs both a challenging benchmark for algorithms and an interesting candidate for cryptographic applications.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
28 pages, 20 figures
The non-Hermitian magnetic moment
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-06 20:00 EDT
Bar Alon, Moshe Goldstein, Roni Ilan
We construct a semiclassical theory for electrons in a non-Hermitian periodic system subject to perturbations varying slowly in space and time. We derive the energy of the wavepacket to first order in the gradients of the perturbations. Applying the theory to the specific case of a uniform external magnetic field, we obtain an expression for the orbital magnetization energy. Using the principles of non-Hermitian dynamics, we define a physically meaningful non-Hermitian generalization of the angular momentum operator and show that it is compatible with the real part of the orbital magnetic moment. The imaginary part of the orbital magnetic moment is also discussed and shown to originate from an imaginary counterpart to the angular momentum that gives rise to a non-Hermitian generalization of the Aharonov-Bohm effect.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics), Quantum Physics (quant-ph)
Modelling the evolution of flow-induced anisotropy of concentrated suspensions
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-06 20:00 EDT
Suspensions, which exhibit complex behaviors such as shear thickening, thinning, and jamming, are prevalent in nature and industry. However, predicting the mechanical properties of concentrated suspensions, in both steady state and the transient regime, remains a significant challenge, impacting product quality and process efficiency. In this study, we focus on developing a robust theoretical framework to explain how flow history governs the anisotropy of mechanical responses in suspensions of hard particles under unsteady flow conditions. Our starting point is the Gillissen-Wilson constitutive model, which we confront to DEM simulation data of the micro-structure during steady shear, and shear rotations where the shear axis is rotated by a specific angle around the flow gradient direction. We introduce a simple modification to the Gillissen-Wilson model which leads to a model with higher predictive power in steady state and during shear rotations.
Soft Condensed Matter (cond-mat.soft)
4 pages, 2 figures, scheduled to be published in “EPJ Web of Conferences’’ (Powders and Grains 2025)
Exciton-Exciton Annihilation Mediated by Many-Body Coulomb and Phonon Interactions: An Ab Initio Study
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-06 20:00 EDT
Guy Vosco, Sivan Refaely-Abramson
Exciton-exciton annihilation (EEA), in which two excitons interact to generate high-energy excitations, is an important non-radiative channel in light-induced excited-state relaxation. When efficient, this process offers an alternative route to exciton emission, potentially allowing extended energetically excited particles’ lifetime and coherence. These properties are significant in designing and understanding materials-based quantum devices, particularly for low-dimensional semiconductors. Here, we present a first-principles framework to compute EEA mechanisms and rates using many-body perturbation theory within the GW and Bethe-Salpeter Equation (GW-BSE) formalism. Our method explicitly accounts for Coulomb-driven and phonon-assisted exciton-exciton scattering by explicitly evaluating the interaction channels between the constituent electrons and holes composing the BSE excitons. We apply this framework to monolayer WSe$ _2$ and explore the $ A$ , $ B$ excitation manifolds, finding picosecond-scale annihilation between bright and dark states, cross valleys, and cross peak manifolds. These channels become allowed due to scattering into free electron-hole pairs across the Brillouin zone. Our results supply new insights into non-radiative exciton relaxation mechanisms in two-dimensional materials, providing a predictive and general tool for modeling these interactions in excitonic materials.
Materials Science (cond-mat.mtrl-sci)
Tensor network method for real-space topology in quasicrystal Chern mosaics
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-06 20:00 EDT
Tiago V. C. Antão, Yitao Sun, Adolfo O. Fumega, Jose L. Lado
Computing topological invariants in two-dimensional quasicrystals and super-moire matter is an exceptional open challenge, due to the absence of translational symmetry and the colossal number of sites inherent to these systems. Here, we establish a method to compute local topological invariants of exceptionally large systems using tensor networks, enabling the computation of invariants for Hamiltonians with hundreds of millions of sites, several orders of magnitude above the capabilities of conventional methodologies. Our approach leverages a tensor-network representation of the density matrix using a Chebyshev tensor network algorithm, enabling large-scale calculations of topological markers in quasicrystalline and moire systems. We demonstrate our methodology with two-dimensional quasicrystals featuring 8-fold and 10-fold rotational symmetries and mosaics of Chern phases. Our work establishes a powerful method to compute topological phases in exceptionally large-scale topological systems, establishing the required tool to rationalize generic super-moire and quasicrystalline topological matter.
Strongly Correlated Electrons (cond-mat.str-el)
7 pages, 3 figures
Hydrodynamic fluctuations of stochastic charged cellular automata
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-06 20:00 EDT
Takato Yoshimura, Žiga Krajnik
We study charge fluctuations of a family of stochastic charged cellular automata away from the deterministic single-file limit and obtain the exact typical charge probability distributions, known to be anomalous, using hydrodynamics. The cellular automata considered are examples of linearly degenerate systems where two distinct mechanisms of diffusion, namely normal and convective diffusion, coexist. Our formalism, based on macroscopic fluctuation theory, allows us to describe current fluctuations stemming from these two diffusive processes, and we expect it to be applicable to generic linearly degenerate systems. The derived probability distributions match the exact microscopic result and numerical simulations.
Statistical Mechanics (cond-mat.stat-mech), Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Theory (hep-th), Mathematical Physics (math-ph)
7+6 pages, 2 figures
Tuning Shear Rheology through Active Dopants
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-06 20:00 EDT
Amir Shee, Ritwik Bandyopadhyay, Haicen Yue
We numerically investigate the shear rheology of mixtures of active and passive Brownian particles, with varying fractions of active components. We find that even a small fraction of active dopants triggers fluidization with comparable efficiency to fully active systems. A combined parameter, active energy, given by dopant fraction multiplied by propulsion speed squared controls the shear rheology and glass transition of the active-passive mixtures. These results together provide a quantitative strategy for fine-tuning the mechanical properties of a soft material with small amounts of active dopants.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
7 pages, 5 figures
Geometric and Nonequilibrium Criticality in Run-and-Tumble Particles with Competing Motility and Attraction
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-06 20:00 EDT
Abir Bhowmick, Sayantan Mitra, P. K. Mohanty
Self-propulsion in run-and-tumble particles (RTPs) generates effective attractive interactions that can drive motility-induced phase separation (MIPS), a phenomenon absent in their passive counterparts. In this work, we show that at high motility, introducing explicit attractive interactions among RTPs can suppress MIPS, leading to a homogeneous phase, and subsequently induce a re-emergence of phase separation at stronger attraction –thus realizing a reentrant phase transition. We characterize this transition by examining the percolation properties of dense clusters, which serve as geometric signatures of phase separation. Along the resulting critical line, we observe continuously varying critical exponents, while some of the associated scaling functions remain invariant and coincide with those of equilibrium lattice gas models undergoing interacting percolation, which is Ising-percolation universality. These findings reveal that the phase separation transition in interacting RTPs exhibits Ising-like super universality, bridging nonequilibrium active matter with classical critical behavior.
Statistical Mechanics (cond-mat.stat-mech)
14 pages, 12 figures (separate this http URL attached)
Nonlinear projection for ballistic correlation functions: a formula in terms of minimal connected covers
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-06 20:00 EDT
In many-body systems, the dynamics is governed, at large scales of space and time, by the hydrodynamic principle of projection onto the conserved densities admitted by the model. This is formalised as local relaxation of fluctuations in the ballistic macroscopic fluctuation theory, a nonlinear Boltzmann-Gibbs principle. We use it to derive a projection formula, expressing n-point connected correlation functions (cumulants) of generic observables at different space-time points, in terms of those of conserved densities. This applies in every d >= 1 spatial dimensions and under the ballistic scaling of space and time, both in and out of equilibrium. It generalises the well-known linear-response principle for 2-point functions. For higher-point functions, one needs to account for nonlinear fluctuations of conserved densities. The result is a nonlinear projection, expressed as a sum over certain products of lower-order correlation functions of conserved densities with equilibrium multivariances as coefficients. Using Malyshev’s formula, the sum is combinatorially organised via certain covers of the set of space-time points, which we call “minimal connected covers”. We use this in order to get general, explicit formulas for two- and three-point functions in stationary states, expressed in terms of thermodynamic and Euler-scale data.
Statistical Mechanics (cond-mat.stat-mech), Mathematical Physics (math-ph)
38 pages, 1 figure
Hydrodynamic noise in one dimension: projected Kubo formula and its vanishing in integrable models
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-06 20:00 EDT
Hydrodynamic noise is the Gaussian process that emerges at larges scales of space and time in many-body systems. It arises by the central limit theorem applied to local microcanonical averages, representing the degrees of freedom that have been forgotten when projecting coarse-grained observables onto conserved quantities. It comes with “bare” diffusion terms. In one dimension of space, nonlinearities of the hydrodynamic equation are relevant (from a renormalisation perspective), usually giving rise to hydrodynamic superdiffusion. But in linearly degenerate systems, where the relevant nonlinearity vanishes, the diffusive scaling stays intact. Nevertheless, anomalies remain. We show that in such systems, the noise covariance is determined in terms of a modification of the Kubo formula, where effects of ballistic long-range correlations have been subtracted. This is the projected Onsager matrix, in which so-called quadratic charges are projected out. We show that the Einstein relation holds, giving a projected bare diffusion, and that the remaining nonlinearities are tamed by a point-splitting regularisation. Putting these ingredients together, we obtain an exact and well-defined hydrodynamic fluctuation theory in the ballistic scaling of space-time, for the asymptotic expansion in the inverse variation scale, including the first subleading (diffusive-scale) corrections beyond large deviations. This is expressed as a stochastic PDE. We then obtain the anomalous hydrodynamic equation, which takes into account separately long-range correlations and bare diffusion. Using these result, in integrable systems, we show that hydrodynamic noise must be absent, as was conjectured recently.
Statistical Mechanics (cond-mat.stat-mech), Mathematical Physics (math-ph)
30 pages
Phase separation in a mixture of proliferating and motile active matter
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-06 20:00 EDT
Lukas Hupe, Joanna M. Materska, David Zwicker, Ramin Golestanian, Bartlomiej Waclaw, Philip Bittihn
Proliferation and motility are ubiquitous drivers of activity in biological systems. Here, we study a dense binary mixture of motile and proliferating particles with exclusively repulsive interactions, where homeostasis in the proliferating subpopulation is maintained by pressure-induced removal. Using computer simulations, we show that phase separation emerges naturally in this system at high density and weak enough self-propulsion. We show that condensation is caused by interactions between motile particles induced by the growing phase, and recapitulate this behavior in an effective model of only motile particles with attractive interactions. Our results establish a new type of phase transition and pave a way to reinterpret the physics of dense cellular populations, such as bacterial colonies or tumors, as systems of mixed active matter.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech), Biological Physics (physics.bio-ph)
6 pages, 4 figures
Transient dynamics of associative memory models
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-06-06 20:00 EDT
Associative memory models such as the Hopfield network and its dense generalizations with higher-order interactions exhibit a “blackout catastrophe”–a discontinuous transition where stable memory states abruptly vanish when the number of stored patterns exceeds a critical capacity. This transition is often interpreted as rendering networks unusable beyond capacity limits. We argue that this interpretation is largely an artifact of the equilibrium perspective. We derive dynamical mean-field equations using a bipartite cavity approach for graded-activity dense associative memory models, with the Hopfield model as a special case, and solve them using a numerical scheme. We show that patterns can be transiently retrieved with high accuracy above capacity despite the absence of stable attractors. This occurs because slow regions persist in the above-capacity energy landscape as shallow, unstable remnants of below-capacity stable basins. The same transient-retrieval effect occurs in below-capacity networks initialized outside basins of attraction. “Transient-recovery curves” provide a concise visual summary of these effects, revealing graceful, non-catastrophic changes in retrieval behavior above capacity and allowing us to compare the behavior across interaction orders. This dynamical perspective reveals rich energy landscape structure obscured by equilibrium analysis and suggests biological neural circuits may exploit transient dynamics for memory retrieval. Furthermore, our approach suggests ways of understanding computational properties of neural circuits without reference to fixed points, advances the technical repertoire of numerical mean-field solution methods for recurrent neural networks, and yields new theoretical results on generalizations of the Hopfield model.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Neurons and Cognition (q-bio.NC)
18 pages, 7 figures
Heterogeneous response and non-Markovianity in the microrheology of semisolid viscoelastic materials
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-06 20:00 EDT
Recent works indicate that heterogeneous response and non-Markovianity may yield recognizable hallmarks in the microrheology of semisolid viscoelastic materials. Here we perform numerical simulations using a non-Markovian overdamped Langevin approach to explore how the microrheology experienced by probe particles immersed in an effective semisolid material can be influenced by its micro-heterogeneities. Our results show that, besides affecting the mean squared displacement, the time-dependent diffusion coefficient, and the shear moduli, the micro-heterogeneities lead to displacement distributions that deviate from the usual Gaussian behavior. In addition, our study provides an analytical way to characterize the micro-heterogeneities of semisolid viscoelastic materials through their microrheology.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech)
9 pages, 4 figures
Landau-Ginzburg Paradigm of Topological Phases
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-06 20:00 EDT
Topologically ordered matter phases have been regarded as beyond the Landau-Ginzburg symmetry breaking paradigm of matter phases. Recent studies of anyon condensation in topological phases, however, may fit topological phases back in the Landau-Ginzburg paradigm. To truly do so, we realized that the string-net model of topological phases is in fact an effective lattice gauge theory coupled with anyonic matter once two modifications are made: (1) We reinterpret anyons as matter fields coupled to lattice gauge fields, thus extending the HGW model to a genuine Hamiltonian lattice gauge theory. (2) By explicitly incorporating the internal degrees of freedom of anyons, we construct an enlarged Hilbert space that supports well-defined gauge transformations and covariant coupling, restoring the analogy with conventional lattice gauge field theory. In this modified string-net model, topological phase transitions induced by anyon condensation and their consequent phenomena, such as order parameter fields, coherent states, Goldstone modes, and gapping gauge degrees of freedom, can be formulated exactly as Landau’s effective theory of the Higgs mechanism. To facilitate the understanding, we also compare anyon condensation to/with the Higgs boson condensation in the electroweak theory and the Cooper pair condensation.
Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Theory (hep-th), Mathematical Physics (math-ph)
50 + 22 pages
A 2D-CFT Factory: Critical Lattice Models from Competing Anyon Condensation Processes in SymTO/SymTFT
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-06 20:00 EDT
Ling-Yan Hung, Kaixin Ji, Ce Shen, Yidun Wan, Yu Zhao
In this paper, we introduce a CFT factory'' : a novel algorithm of methodically generating 2D lattice models that would flow to 2D conformal fixed points in the infrared. These 2D models are realised by giving critical boundary conditions to 3D topological orders (symTOs/symTFTs) described by string-net models, often called the strange correlators. We engineer these critical boundary conditions by introducing a commensurate amount of non-commuting anyon condensates. The non-invertible symmetries preserved at the critical point can be controlled by studying a novel refined condensation tree’’. Our structured method generates an infinite family of critical lattice models, including the A-series minimal models, and uncovers previously unknown critical points. Notably, we find at least three novel critical points (c$ \approx 1.3$ , $ 1.8$ , and $ 2.5$ respectively) preserving the Haagerup symmetries, in addition to recovering previously reported ones. The condensation tree, together with a generalised Kramers-Wannier duality, predicts precisely large swathes of phase boundaries, fixes almost completely the global phase diagram, and sieves out second order phase transitions. This is not only illustrated in well-known examples (such as the 8-vertex model related to the $ A_5$ category) but also further verified with precision numerics, using our improved (non-invertible) symmetry-preserving tensor-network RG, in novel examples involving the Haagerup symmetries. We show that critical couplings can be precisely encoded in the categorical data (Frobenius algebras and quantum dimensions in unitary fusion categories), thus establishing a powerful, systematic route to discovering and potentially classifying new conformal field theories.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Theory (hep-th), Mathematical Physics (math-ph)
47 pages + appendices, 20 figures
Spinless and spinful charge excitations in moiré Fractional Chern Insulators
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-06 20:00 EDT
Miguel Gonçalves, Juan Felipe Mendez-Valderrama, Jonah Herzog-Arbeitman, Jiabin Yu, Xiaodong Xu, Di Xiao, B. Andrei Bernevig, Nicolas Regnault
Fractionally charged elementary excitations, the quasi-electron and quasi-hole, are one of the hallmarks of the fractional Chern insulator (FCI). In this work, we observe that spontaneous spin polarization in twisted MoTe$ _2$ leads to multiple species of low-energy quasi-particles distinguished by their spin quantum numbers. We perform large-scale exact diagonalization (ED) calculations to investigate the nature of these excitations and develop a method to extract their fundamental energetic properties. Focusing on $ \theta = 3.7^{\circ}$ and filling factor $ \nu = -2/3$ relevant to recent experiments, we show that spin-preserving (spinless) charge excitations have smaller gap than spin-flipping (spinful) excitations both with and without band mixing. This result is in qualitative agreement with the measured magnetic field dependence of the transport gaps. Beyond the spinless and spinful quasi-particle gaps, we extract the full quasi-electron and quasi-hole ``band structure’’ and find significant dispersion with emergent magnetic translation symmetry – a fundamental departure from the immobile excitations of the quantum Hall fluid. Our results establish a framework for computing the properties of novel elementary excitations in FCIs.
Strongly Correlated Electrons (cond-mat.str-el)