CMP Journal 2025-06-20
Statistics
Nature Materials: 1
Nature Physics: 1
arXiv: 61
Nature Materials
Nonlinear transport in non-centrosymmetric systems
Review Paper | Electronic properties and materials | 2025-06-19 20:00 EDT
Manuel Suárez-Rodríguez, Fernando de Juan, Ivo Souza, Marco Gobbi, Fèlix Casanova, Luis E. Hueso
Ohm’s law has been a cornerstone of electronics since its experimental discovery. This law establishes that, in a conductive system, the voltage is directly proportional to the current. Even when time-reversal symmetry is disrupted, leading to the emergence of magnetoresistance and Hall effects, the linear relationship between voltage and current remains intact. However, recent experiments have demonstrated a breakdown of Ohm’s law in non-centrosymmetric structures. In these systems, nonlinear transport effects are permitted with quadratic scaling between voltages and currents. Here we review the main demonstrations of nonlinear transport in non-centrosymmetric systems, analysing the connection between nonlinear behaviour and the system’s symmetry. We also investigate the microscopic mechanisms driving these effects, such as Berry curvature dipole and Berry connection polarizability. Finally, we highlight potential applications of nonlinear transport in spintronics and energy harvesting.
Electronic properties and materials, Topological matter
Nature Physics
Intercellular flow dominates the poroelasticity of multicellular tissues
Original Paper | Biophysics | 2025-06-19 20:00 EDT
Fan Liu, Bo Gao, Liran Lei, Shuainan Liu, Hui Li, Ming Guo
The mechanical characteristics of cells and extracellular matrices–such as elasticity, surface tension and viscosity–can influence diseases such as fibrosis and tumour metastasis. Multicellular tissues have traditionally been modelled as viscoelastic materials, which overlooked the abundance of intercellular space and intercellular flow within the structure. Although intercellular flow can substantially impact development and disease progression, its role in the mechanical behaviour of tissues remains unclear. Here we show that fluid transport via the intercellular space determines the immediate mechanical response of tissues upon deformation. We directly measure the mechanical response of multicellular tissues by applying parallel plate compression via a tailored micro-mechanics platform. We find that both cultured three-dimensional cell spheroids and native mouse pancreatic islets exhibit apparent poroelastic behaviour over a timescale of up to a minute. These findings highlight the fundamental role of interstitial fluid transport in the mechanics of multicellular systems and could help identify potential physical regulators of development and diseases, as well as strategies for engineering multicellular living systems.
Biophysics, Soft materials
arXiv
Non-degenerate Ground State of the Spin-Boson Model under Abelian Diagonalization
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-19 20:00 EDT
By utilizing a unitary transformation, we derive the necessary and sufficient conditions for the degeneracy between the even- and odd-parity energy states of the spin-boson model (SBM). Employing the Rayleigh quotient of matrix algebra, we rigorously prove that the ground state energy of the SBM is lower than the systems lowest possible degenerate energy and possesses a definite parity. Based on the necessary and sufficient conditions for parity breaking, we provide an analytical expression for the parity-breaking critical value, which is closely related to the expansion order and computational accuracy. This expression reproduces the SBM phase diagram obtained by quantum Monte Carlo (QMC) and logarithmic discretization numerical renormalization group (NRG) methods. However, this phase diagram does not characterize the ground state of the system.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
Time-domain decoding of unconventional charge order mechanisms in nonmagnetic and magnetic kagome metals
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-19 20:00 EDT
Seongyong Lee, Byungjune Lee, Hoyoung Jang, Xueliang Wu, Jimin Kim, Gyeongbo Kang, Choongjae Won, Hyeongi Choi, Sang-Youn Park, Kyle M. Shen, Federico Cilento, Aifeng Wang, Jae-Hoon Park, Mingu Kang
In kagome lattice materials, quantum interplay between charge, spin, orbital, and lattice degrees of freedom gives rise to a remarkably rich set of emergent phenomena, ranging from unconventional charge order and superconductivity to topological magnetism. While the exact nature of these exotic orders is often challenging to comprehend in static experiments, time-resolved techniques can offer critical insights by disentangling coupled degrees of freedom on the time-axis. In this work, we demonstrate that the nature of charge orders in two representative kagome metals - nonmagnetic ScV6Sn6 and magnetic FeGe - which has been highly controversial in static studies, can be directly deciphered in the time-domain through their fundamentally distinct order parameter dynamics measured via time-resolved X-ray scattering at an X-ray free electron laser. In nonmagnetic ScV6Sn6, the dynamics are characterized by ultrafast melting and coherent amplitudon oscillations, typical of a phonon-coupled charge order. In stark contrast, magnetic FeGe exhibits resilient metastable charge order dynamics, hitherto unobserved in any other charge-ordered system - this unique time-domain behavior directly signifies an unconventional magnetism-interlocked charge order state realized in this kagome magnet. Our results not only provide a model case where unconventional nature of electronic order, hidden in equilibrium, is directly unraveled in the time-domain, but also pave the way for future out-of-equilibrium engineering of novel quantum orders in kagome lattice platforms.
Strongly Correlated Electrons (cond-mat.str-el)
4 figures
Non-linear in-plane spin current in spin-orbit coupled 2D hole gases
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-19 20:00 EDT
Srijan Chatterjee, Tarun Kanti Ghosh
The non-linear transport of charge and spin due to the emergence of band geometric effects has garnered much interest in recent years. In this work, we show that a linear in-plane spin current vanishes, whereas a non-linear (second-order) in-plane spin current exists for a generic two-dimensional system having time-reversal symmetry. The intrinsic second-order spin current originates from the spin Berry curvature polarizability. The formulation when applied to 2D hole gases with the $ k^3$ Rashba spin-orbit interaction reveals the existence of both transverse and longitudinal second-order in-plane spin currents normal to the spin orientation. Further, the effects of band anisotropy due to additional Dresselhaus spin-orbit interaction or an electromagnetic radiation are explored, which allows the generation of additional in-plane spin currents parallel to the spin orientation in the same system. The time-reversal symmetry also prevents any out-of-plane spin current in the second-order. The generation and control over the multiple in-plane spin currents may have important applications in spintronic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
10 pages, 7 figures
Inverse method for determining general molecular weight distribution from polymer rheology
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-19 20:00 EDT
Nihal Pushkar, Xin C. Yee, Jena McCollum, Brandon Runnels
Determination of polymer molecular weight distribution (MWD) from rheological measurements is desirable due to the ease and low cost of rheometry compared to other methods such as gel permeation chromatography. However, relating MWD to rheology requires the inversion of rheological models, for which there is no analytic solution. Prior approaches assume a functional form for the MWD (such as a lognormal or generalized exponential distribution), minimizing the error with respect to the functional form’s degrees of freedom. While this is a powerful and robust technique for determining general polymer properties, such as average MWD or polydispersity, it requires former knowledge of the shape of the MWD. This work presents a generalized approach to solving the inverse problem directly, with no former knowledge of the MWD or assumptions regarding its functional form. To close the inverse problem and establish uniqueness, Lagrange multipliers constraints on the MWD are included. The method is applied with reptation-based models to a variety of polycarbonate, polyethylene and polystyrene polymers. For samples whose rheology are well-described by reptation, the predicted MWD is shown to match experimental measurements very well. For samples that are not well-described by reptation, the predicted MWD naturally differs from experiment. Nevertheless, the results still offer insight into how reptation-described polymers differ from their counterparts. This establishes the proposed inverse method as a viable practical tool for rheology-based characterization.
Soft Condensed Matter (cond-mat.soft)
Quantum and Semi-Classical Signatures of Dissipative Chaos in the Steady State
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-19 20:00 EDT
Griffith Rufo, Sabrina Rufo, Pedro Ribeiro, Stefano Chesi
We investigate the quantum-classical correspondence in open quantum many-body systems using the SU(3) Bose-Hubbard trimer as a minimal model. Combining exact diagonalization with semiclassical Langevin dynamics, we establish a direct connection between classical trajectories characterized by fixed-point attractors, limit cycles, or chaos and the spectral and structural properties of the quantum steady state. We show that classical dynamical behavior, as quantified by the sign of the Lyapunov exponent, governs the level statistics of the steady-state density matrix: non-positive exponents associated with regular dynamics yield Poissonian statistics, while positive exponents arising from chaotic dynamics lead to Wigner-Dyson statistics. Strong symmetries constrain the system to lower-dimensional manifolds, suppressing chaos and enforcing localization, while weak symmetries preserve the global structure of the phase space and allow chaotic behavior to persist. To characterize phase-space localization, we introduce the phase-space inverse participation ratio IPR, which defines an effective dimension D of the Husimi distribution’s support. We find that the entropy scales as $ S \propto \ln N^D$ , consistently capturing the classical nature of the underlying dynamics. This semiclassical framework, based on stochastic mixtures of coherent states, successfully reproduces not only observable averages but also finer features such as spectral correlations and localization properties. Our results demonstrate that dissipative quantum chaos is imprinted in the steady-state density matrix, much like in closed systems, and that the interplay between dynamical regimes and symmetry constraints can be systematically probed using spectral and phase-space diagnostics. These tools offer a robust foundation for studying ergodicity, localization, and non-equilibrium phases of open quantum systems.
Statistical Mechanics (cond-mat.stat-mech), Chaotic Dynamics (nlin.CD), Quantum Physics (quant-ph)
24 pages, 13 fugures
Quasi-1D Coulomb drag between spin-polarized quantum wires
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-19 20:00 EDT
Mingyang Zheng, Rebika Makaju, Rasul Gazizulin, Alex Levchenko, Sadhvikas J. Addamane, Dominique Laroche
One-dimensional (1D) quantum wires provide a versatile platform for studying strong electron-electron interactions and collective excitations under confinement. Coulomb drag between 1D systems offers a powerful probe of Tomonaga-Luttinger liquid (TLL) physics, with theoretical predictions suggesting distinct power-law in temperature dependencies between the spin-full and the spin-polarized regimes. However, experimental verification has thus far remained limited. Here, we report measurements of reciprocal and nonreciprocal Coulomb drag between vertically coupled quasi-1D quantum wires in the spin-polarized regime. Clear signatures of spin splitting are observed in both the wires conductance and the drag signal. We observed a connection between electron-hole asymmetry and negative drag, and demonstrated different power-law behaviors in spin-full and spin-polarized regimes, yielding consistent TLL interaction parameters. These results validate the theoretical predictions for backscattering induced drag in the reciprocal regime and extend them to the nonreciprocal and the multiple subband regimes. Furthermore, the nonmonotonic density dependence of the reciprocal interaction parameter correlates with the subband occupation of the drag wire, revealing the complexity of the scattering mechanisms in multichannel systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 4 figures
Graphene Nanoribbons as a Majorana Platform
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-19 20:00 EDT
Ruize Ma, Michele Pizzochero, Gaurav Chaudhary
Graphene nanoribbons support a range of electronic phases that can be controlled via external stimuli. Zigzag-edged graphene nanoribbons (ZGNRs), in particular, exhibit an antiferromagnetic insulating ground state that transitions to a half-metallic phase under a transverse electric field or when embedded inside hexagonal Boron Nitride. Here, we consider a simple model of a heterostructure of a ZGNR with an Ising superconductor and show that, the Ising superconductor with a parent s-wave spin-singlet pairing can induce spin-triplet odd-parity pairing in the half-metallic phase of the ZGNR. The resulting superconducting phase is topologically nontrivial, with gate-tunable transitions that enable the emergence of Majorana zero modes.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Electronic properties of multilayered Lieb, transition, and Kagome lattices
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-19 20:00 EDT
T. F. O. Lara, E. B. Barros, W. P. Lima, J. P. G. Nascimento, J. Milton Pereira Jr., T. A. S. Pereira, D. R. da Costa
Based on the interconvertibility feature shared between monolayer Lieb and Kagome lattices, which allows mapping transition lattice’s stages between these two limits ($ \pi/2 \leq\theta \leq 2\pi/3$ ), in this work we extend the recently proposed one-control ($ \theta$ ) parameter tight-binding model for the case of a multilayer Lieb-Kagome system, by considering the two most-common stacks: AA and AB (Bernal). We systematically study the band transformations between the two lattices by adjusting the interlayer hopping and distance, with or without considering the influence of the nearest interlayer neighbors, for different numbers of stacked layers, and under the application of an external perpendicular electric field. The energetic changes are understood from the perspective of the layer dependence of the pseudospin components and the total probability density distributions. The present framework provides an appropriate and straightforward theoretical approach to continuously investigate the evolution of electronic properties in the multilayer Lieb-Kagome system under various external effects.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
23 pages, 11 figures
Interplay of Zeeman field, Rashba spin-orbit interaction, and superconductivity: spin susceptibility
New Submission | Superconductivity (cond-mat.supr-con) | 2025-06-19 20:00 EDT
We present a self-consistent theory to calculate the static and uniform spin susceptibility in superconductors under simultaneous Zeeman magnetic fields and Rashba-type spin-orbit coupling (SOC). Employing a single-band Bogoliubov-de Gennes Hamiltonian, we solve the gap equation for both conventional $ s$ -wave spin-singlet and six representative $ p$ -wave spin-triplet pairing states, categorized into opposite-spin-pairing (OSP) and equal-spin-pairing (ESP) classes. The Kubo formula, decomposed into intra- and interband particle-hole and particle-particle channels, provides two key constraints: at zero temperature, only particle-particle terms contribute, while at the critical temperature $ T_c$ , only particle-hole terms remain, ensuring $ \chi(T_c^{-}) = \chi_N$ for continuous phase transitions. For $ s$ -wave pairing, a Zeeman field reduces $ T_c$ , whereas Rashba SOC preserves $ T_c$ but yields a residual zero temperature spin susceptibility $ \chi(0)$ which approaches $ 2\chi_N/3$ in the strong SOC limit; combined fields create a Bogoliubov Fermi surface, resulting in a kink in $ \chi(0)$ . In contrast, $ p$ -wave states exhibit strong anisotropy: OSP states mimic spin-singlet pairing behavior for parallel Zeeman fields and ESP for transverse ones, while ESP states show the opposite, with Rashba SOC potentially changing the quasiparticle nodal structure, lowering $ T_c$ , or causing $ \chi_{zz}(0)$ divergences. This framework offers quantitative benchmarks for Knight-shift experiments in non-centrosymmetric superconductors like A$ _2$ Cr$ _3$ As$ _3$ (A = Na, K, Rb, and Cs), enabling diagnostics to disentangle pairing symmetry, SOC strength, and Zeeman effects.
Superconductivity (cond-mat.supr-con)
14+10 pages
Strongly coupled interface ferroelectricity and interface superconductivity in LAO/KTO
New Submission | Superconductivity (cond-mat.supr-con) | 2025-06-19 20:00 EDT
M.D. Dong, X.B. Cheng, M. Zhang, J. Wu
Interfaces can differ from their parent compounds in terms of charge, spin, and orbital orders and are fertile ground for emergent phenomena, strongly correlated physics, and device applications. Here, we discover that ferroelectric order resides at the interface of two oxides, LaAlO3/KTaO3(111) (LAO/KTO), where two seemingly mutually exclusive orders-ferroelectricity and superconductivity-coexist. Moreover, manipulating ferroelectricity can change the interfacial conductivity by more than 1000 times, simultaneously causing superconductivity to diminish and reappear due to the coupling between these phenomena. The ferroelectricity is confirmed by scanning transmission electron microscopy (STEM), second harmonic generation (SHG) microscopy, and piezoelectric force microscopy (PFM). STEM reveals K ions are displaced relative to Ta ions, with the help of oxygen vacancies at the LAO/KTO interface. The resultant electric polarization is locally switchable by applying a voltage between the PFM tip and the LAO film. The ferroelectric hysteresis correlates with hysteresis change in interfacial conductivity and the superconducting transition temperature (Tc). The loss and reentrance of superconductivity are accounted for by orders of magnitude change in the Hall mobility induced by the polarization switching. These findings open the door to ferroelectric superconductivity with broken inversion symmetry and non-volatile modulation of superconductivity.
Superconductivity (cond-mat.supr-con)
Moiré-Polaritons in a Dark Bose-Einstein Condensate
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-19 20:00 EDT
Moroni Santiago-García, Shunashi G. Castillo-López, David A. Ruiz-Tijerina, Arturo Camacho-Guardian
Quantum mixtures of moiré excitons have arisen as a platform for realizing novel phases of light and matter. Here, we study moiré polaritons coupled to a Bose-Einstein condensate of dark-state excitons confined to a moiré superlattice. We develop a variational approach to analyze the optical response of the system and demonstrate that strong exciton-exciton interactions significantly modify the character of moiré polaritons, leading to sizable energy shifts of the avoided crossing between the principal polariton branches, and the emergence of an additional, stable repulsive-polariton bound state.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Gases (cond-mat.quant-gas)
5 + 3 pages, 3 figures. Comments are very welcome
Tuning spin-density separation via finite-range interactions: Dimensionality-driven signatures in dynamic structure factors
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-06-19 20:00 EDT
Xiaoran Ye, Yi Zhang, Ziheng Zhou, Zhaoxin Liang
Spin-density separation, marked by distinct propagation velocities of spin and density excitations, epitomizes strong correlations, historically confined to one-dimensional (1D) systems. Recent ultracold quantum gas experiments, however, demonstrate its emergence in higher dimensions through precise tuning of intra- to interspecies interaction ratios, inspiring exploration of how dimensionality and interatomic interactions govern quantum correlations. We investigate this in two-component bosonic mixtures with finite-range interactions, probing 1D and three-dimensional (3D) dynamics. Using effective field theory within the one-loop approximation, we derive analytical expressions for zero-temperature ground-state energy and quantum depletion, seamlessly recovering contact interaction results in the contact limit. By crafting an effective action for decoupled density and spin modes, we compute dynamic structure factors (DSFs), revealing how finite-range interactions sculpt spin-density separation. A pivotal finding is the dimensionality-driven divergence in DSF peak dynamics: in 1D, peaks ascend to higher frequencies with increasing interaction strength, yielding sharp responses; in 3D, peaks descend to lower frequencies, with broader density wave profiles. These insights highlight dimensionality’s critical role in collective excitations and provide a robust theoretical blueprint for probing interaction-driven quantum phenomena via Bragg spectroscopy, paving new pathways for exploring dimensionally tuned quantum correlations in ultracold quantum gases.
Quantum Gases (cond-mat.quant-gas)
15 pages, 4 figures
Coherent tunneling of collective excitation of Bose-Einstein condensate in a double-well potential
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-06-19 20:00 EDT
Yaojun Ying, Haoyu Wang, Ming Zhang, Haibin Li
The Josephson effect can be observed in a Bose-Einstein condensate in a double-well potential, which is attributed to the tunneling of bosons between two wells. We propose a multi-mode theory to investigate the dynamics of local excitations in a one-dimensional condensate in a double-well potential. We show that the system can be described by two independent two-mode models. The Josephson oscillation and the self-trapping of local collective excitations are predicted analytically and confirmed by numerical simulation.
Quantum Gases (cond-mat.quant-gas)
6 pages
High-Throughput Computation of Anharmonic Low-Frequency Protein Vibrations
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-19 20:00 EDT
Michael A. Sauer, Souvik Mondal, Madeline Cano, Matthias Heyden
At room temperature, low frequency vibrations at far-infrared frequencies are thermally excited ($ k_B T > h \nu$ ) and not restricted to harmonic fluctuations around a single potential energy minimum. For folded proteins, these intrinsically anharmonic vibrations can contain information on slow conformational transitions. Recently, we have developed FREquency-SElective ANharmonic (FRESEAN) mode analysis, a method based on time correlation functions that isolates low-frequency vibrational motions from molecular dynamics simulation trajectories without relying on harmonic approximations. We recently showed that low-frequency vibrations obtained from FRESEAN mode analysis are effective collective variables in enhanced sampling simulations of conformational ensembles. However, FRESEAN mode analysis is based on velocity time correlations between all degrees of freedom, which creates computational challenges for large biomolecules. To facilitate future applications, we demonstrate here how coarse-graining of all-atom simulation trajectories can be combined with FRESEAN mode analysis to extract information on low-frequency vibrations at minimal computational cost.
Statistical Mechanics (cond-mat.stat-mech), Computational Physics (physics.comp-ph)
19 pages, 13 figures
Generative thermodynamic computing
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-19 20:00 EDT
We introduce a generative modeling framework for thermodynamic computing, in which structured data is synthesized from noise by the natural time evolution of a physical system governed by Langevin dynamics. While conventional diffusion models use neural networks to perform denoising, here the information needed to generate structure from noise is encoded by the dynamics of a thermodynamic system. Training proceeds by maximizing the probability with which the computer generates the reverse of a noising trajectory, which ensures that the computer generates data with minimal heat emission. We demonstrate this framework within a digital simulation of a thermodynamic computer. If realized in analog hardware, such a system would function as a generative model that produces structured samples without the need for artificially-injected noise or active control of denoising.
Statistical Mechanics (cond-mat.stat-mech), Neural and Evolutionary Computing (cs.NE)
Benchmarks for protocol control in nonequilibrium statistical mechanics
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-19 20:00 EDT
Stephen Whitelam, Corneel Casert, Megan Engel, Isaac Tamblyn
We present a set of computer codes designed to test methods for optimizing time-dependent control protocols in fluctuating nonequilibrium systems. Each problem consists of a stochastic model, an optimization objective, and C++ and Python implementations that can be run on Unix-like systems. These benchmark systems are simple enough to run on a laptop, but challenging enough to test the capabilities of modern optimization methods. This release includes five problems and a worked example. The problem set is called NESTbench25, for NonEquilibrium STatistical mechanics benchmarks (2025).
Statistical Mechanics (cond-mat.stat-mech)
A Coordination-Based Model for the Prediction of Surface Energies and the Shape of Metal Particles
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
Shyama Charan Mandal, Frank Abild-Pedersen
Surface energies of metal-based systems are important for determining the Wulff-constructed shapes of metal nanoparticles and understanding the stability. We have developed a coordination number-based model to predict the total energy of metal-based systems across a wide range of configurations. Our model has been tested against Density Functional Theory (DFT) calculations for late transition metals. This method enables on-the-fly surface energy predictions and allows for the Wulff construction of metal particles for a random number of elemental atoms and without the need for DFT calculations. By making a division between atoms in the different layers of the model system we can considerably improve the accuracy of the model, suggesting a dissimilarity between the electronic structure due to an alternating compression and expansion of atomic layers in the near-surface region. We find that our model accurately and effectively provides valuable insights into the distribution and stability of nanoparticle surfaces.
Materials Science (cond-mat.mtrl-sci)
Random walk with multiple memory channels: a new paradigm
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-19 20:00 EDT
A new class of one-dimensional, discrete time random walk model with memory, termed “Random walk with $ n$ memory channels” (RW$ n$ MC) is proposed. In this model the information of $ n$ ($ n\in \mathbb{Z}$ ) previous steps from the walker’s entire history are needed to decide future step. Exact calculation of the mean and variance of position of the RW2MC ($ n=2$ ) has been done which shows that it can lead to asymptotic diffusive and superdiffusive behavior in different parameter regimes. A connection between RW$ n$ MC and Pólya type urn model evolving by $ n$ drawings has also been reported. This connection for the RW2MC is discussed in detail which suggests the applicability of RW$ 2$ MC in many population dynamics model with multiple competing species.
Statistical Mechanics (cond-mat.stat-mech)
Phys. Rev. E 106, L062105 (2022)
Fundamentals of the metal contact to p-type GaN: new multilayer design
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
Konrad Sakowski, Paweł Strak, Stanislaw Krukowski
Electrical properties of contact to p-type nitride semiconductor devices, based on gallium nitride were simulated by ab initio and by drift-diffusion calculations. The contact electric properties are shown to be dominated by electron transfer form metal to GaN related to Fermi level difference both by ab initio and model calculation. The results indicate on high potential barrier for holes leading to nonohmic character of the contact. The electrical nature of the Ni-Au contact formed by annealing in oxygen atmosphere is elucidated. The doping influence on the potential profile in p-type GaN was calculated by in drift-diffusion model. The energy barrier height and width for hole transport is determined. Based on these results, new type of the contact, is proposed. The contact is created employing multiple layer implantation of the deep acceptors. The implementation of such design promise to attain superior characteristics (resistance) as compared to other contacts used in bipolar nitride semiconductor devices. The development of such contact will remove one of the main obstacles in the development of highly efficient nitride optoelectronic devices both LEDs and LDs: energy loss and the excessive heat production close to the multiple quantum wells system
Materials Science (cond-mat.mtrl-sci)
22 pages 9 figures
Effect of Rashba spin-orbit coupling on topological phases in monolayer ZnIn2Te4
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-19 20:00 EDT
The interplay of Rashba and quantum spin Hall effects in non-centrosymmetric systems presents both challenges and opportunities for spintronic applications. While Rashba spin-orbit coupling can disrupt the quantum spin Hall phase, their coexistence may enable additional spintronic functionalities by coupling spin-momentum locking in the bulk with topologically protected edge states. Using the ZnIn$ _2$ Te$ _4$ monolayer as a case study-a predicted polar two-dimensional topological insulator-we investigate how intrinsic and Rashba spin-orbit coupling compete within a single material. Our results identify key conditions under which sizable Rashba spin splitting can coexist with a stable quantum spin Hall phase, offering guidance for engineering quantum spin Hall insulators with enhanced spintronic capabilities.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Phys. Rev. B (2025)
Segregation and cooperation in active colloidal binary mixtures
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-19 20:00 EDT
Laura Alvarez, Elena Sesé-Sansa, Demian Levis, Ignacio Pagonabarraga, Lucio Isa
The complex interactions underlying collective motion in biological systems give rise to emergent behaviours such as flocking, sorting, and cooperative transport. These dynamics often involve species with different motilities coordinating movement to optimize navigation and survival. Synthetic analogues based on active colloids offer a controlled platform to explore such behaviours, yet most experimental realizations remain limited to monodisperse systems or mixtures of passive and active particles. Here, we investigate dense binary mixtures of active Janus colloids with distinct motilities and independently tunable alignment, actuated by AC electric fields. We demonstrate experimentally and numerically that both species form highly dynamic polar clusters, with alignment emerging independently of propulsion speed. In mixed populations, interspecies interactions lead to effective segregation and cooperative motion, including transient enhancement of slower particle motility. Our results reveal how motility contrast and alignment combine to drive self-organization in active mixtures, offering strategies for designing reconfigurable materials with collective functionalities.
Soft Condensed Matter (cond-mat.soft)
Impact of Mechanical Stress on IGZO TFTs: Enhancing PBTI Degradation
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
K. Vishwakarma, K. Lee, A. Kruv, A. Chasin, M. J. van Setten, C. Pashartis, O. O. Okudur, M. Gonzalez, N. Rassoul, A. Belmonte, B. Kaczer
This study investigates the impact of out-of-plane compressive mechanical stress (MS) on the performance and reliability of n-channel IGZO thin film transistors (TFTs). It is demonstrated that MS induces a positive Vth shift in the device transfer characteristics and enhances electron trapping during Positive Bias Temperature Instability (PBTI) tests. These effects are attributed to the widening of the IGZO bandgap (EG) and increased accessibility of carriers to AlOX gate oxide trap levels. As substantial residual MS is generated in 3D device processing, understanding its impact on IGZO TFTs is crucial for enabling future 3D DRAM technology.
Materials Science (cond-mat.mtrl-sci)
2025 IEEE International Reliability Physics Symposium (IRPS), Monterey, CA, USA, 2025, pp. 1-6
Autonomous life-like behavior emerging in active and flexible microstructures
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-19 20:00 EDT
Many organisms leverage an interplay between shape and activity to generate motion and adapt to their environment. Embedding such feedback into synthetic microrobots could eliminate the need for sensors, software, and actuators, yet current realizations are either active but rigid, or flexible but passive. Here, we introduce micrometer-scale structures that integrate both activity and flexibility by 3D microprinting concatenated units and actuating them with an AC electric field. This minimal yet versatile design gives rise to a rich array of life-like modes of motion - including railway and undulatory locomotion, rotation, and beating - as well as emergent sense-response abilities, which enable autonomous reorientation, navigation, and collision avoidance. Our approach offers a versatile platform for designing biomimetic model systems and autonomously operating microrobots with embodied intelligence.
Soft Condensed Matter (cond-mat.soft)
27 pages
Algal Optics
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-19 20:00 EDT
Ming Yang, Sumit Kumar Birwa, Raymond E. Goldstein
Nearly a decade ago it was discovered that the spherical cell body of the alga $ Chlamydomonas~reinhardtii$ can act as a lens to concentrate incoming light onto the cell’s membrane-bound photoreceptor and thereby affect phototaxis. Since many nearly transparent cells in marine environments have complex, often non-axisymmetric shapes, this observation raises fundamental, yet little-explored questions in biological optics about light refraction by the bodies of microorganisms. There are two distinct contexts for such questions: the $ absorption$ problem for $ incoming$ light, typified by photosynthetic activity taking place in the chloroplasts of green algae, and the $ emission$ problem for $ outgoing$ light, where the paradigm is bioluminescence emitted from scintillons within dinoflagellates. Here we examine both of these aspects of ``algal optics” in the special case where the absorption or emission is localized in structures that are small relative to the overall organism size, taking into account both refraction and reflections at the cell-water boundary. Analytical and numerical results are developed for the distribution of light intensities inside and outside the body, and we establish certain duality relationships that connect the incoming and outgoing problems. For strongly non-spherical shapes we find lensing effects that may have implications for photosynthetic activity and for the angular distribution of light emitted during bioluminescent flashes.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph), Subcellular Processes (q-bio.SC)
15 pages, 10 figures
Dynamic buckling of Si tetramers on the Si(111)-7x7
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
R. Zhachuk, J. Coutinho, D. Sheglov
The atomic structure of Si tetramers that form on the Si$ (111)\textrm{-}7\times7$ surface during homoepitaxy, is investigated by means of first principles calculations with the currently available atomistic model as starting point. It is demonstrated that the rectangular shape of the Si tetramer is unstable against buckling. Comparison of calculated results with available scanning tunnelling microscopy (STM) data provides a new understanding of the problem, indicating that the recorded STM images are influenced by dynamic buckling.
Materials Science (cond-mat.mtrl-sci)
Journal of Chemical Physics 162, 234704 (2025)
An efficient forgetting-aware fine-tuning framework for pretrained universal machine-learning interatomic potentials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
Jisu Kim, Jiho Lee, Sangmin Oh, Yutack Park, Seungwoo Hwang, Seungwu Han, Sungwoo Kang, Youngho Kang
Pretrained universal machine-learning interatomic potentials (MLIPs) have revolutionized computational materials science by enabling rapid atomistic simulations as efficient alternatives to ab initio methods. Fine-tuning pretrained MLIPs offers a practical approach to improving accuracy for materials and properties where predictive performance is insufficient. However, this approach often induces catastrophic forgetting, undermining the generalizability that is a key advantage of pretrained MLIPs. Herein, we propose reEWC, an advanced fine-tuning strategy that integrates Experience Replay and Elastic Weight Consolidation (EWC) to effectively balance forgetting prevention with fine-tuning efficiency. Using Li$ _6$ PS$ _5$ Cl (LPSC), a sulfide-based Li solid-state electrolyte, as a fine-tuning target, we show that reEWC significantly improves the accuracy of a pretrained MLIP, resolving well-known issues of potential energy surface softening and overestimated Li diffusivities. Moreover, reEWC preserves the generalizability of the pretrained MLIP and enables knowledge transfer to chemically distinct systems, including other sulfide, oxide, nitride, and halide electrolytes. Compared to Experience Replay and EWC used individually, reEWC delivers clear synergistic benefits, mitigating their respective limitations while maintaining computational efficiency. These results establish reEWC as a robust and effective solution for continual learning in MLIPs, enabling universal models that can advance materials research through large-scale, high-throughput simulations across diverse chemistries.
Materials Science (cond-mat.mtrl-sci)
25 pages, 8 figures, Supplementary information included as ancillary file (+16 pages)
Subthreshold Swing Behavior in Amorphous Indium-Gallium-Zinc-Oxide Transistors from Room to Cryogenic Temperatures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
Hongwei Tang, Attilio Belmonte, Dennis Lin, Ying Zhao, Arnout Beckers, Patrick Verdonck, Harold Dekkers, Subhali Subhechha, Michiel van Setten, Zhuo Chen, Gouri Sankar Kar, Jan Van Houdt, Valeri Afanas’ev
While cryogenic-temperature subthreshold swing (SS) in crystalline semiconductors has been widely studied, a careful study on the temperature-dependent SS in amorphous oxide semiconductors remains lacking. In this paper, a comprehensive analysis of the SS in thin-film transistors with an amorphous indium gallium zinc oxide (IGZO) channel at temperatures from 300 K down to 4 K is presented. Main observations include: 1) At room temperature (300 K), the devices exhibit a SS of 61 mV/dec, and a low interface trap density (<1011 cm-2), among the best reported values for IGZO devices. 2) A SS saturation around 40 mV/dec is observed between 200 K and 100 K. It is well explained by the electron transport via band tail states with exponential decay (Wt) of 13 meV. 3) At deep-cryogenic temperature, SS increase significantly exceeding 200 mV/dec at 4 K. Such high SS values are actually limited by the measurement current range, confirmed by Id-Vg simulations based on the variable range hopping (VRH) model. This work not only elucidates the SS behavior in amorphous IGZO devices but also provides a deep understanding of the physical mechanisms of electron transport in amorphous semiconductors.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
Appl. Phys. Lett. 126, 232108 (2025)
Ferroelectric switching control of spin current in graphene proximitized by In$_2$Se$_3$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
Marko Milivojević, Juraj Mnich, Paulina Jureczko, Marcin Kurpas, Martin Gmitra
By utilizing the proximity effect, we introduce a platform that exploits ferroelectric switching to modulate spin currents in graphene proximitized by ferroelectric In$ _2$ Se$ _3$ monolayer. Through first-principles calculations and tight-binding modeling, we studied the electronic structure of graphene/In$ _2$ Se$ _3$ heterostructure for twist angles of 0$ ^{\circ}$ and 17.5$ ^{\circ}$ , considering both ferroelectric polarizations. We discover that switching the ferroelectric polarization reverses the sign of the charge-to-spin conversion coefficients, acting as a chirality switch of the in-plane spin texture in graphene. For the twisted heterostructure, we observed emergence of unconventional radial Rashba field for one ferroelectric polarization direction. Additionally, we demonstrated that the Rashba phase can be directly extracted from the ratio of conversion efficiency coefficients, providing a straightforward approach to characterize the in-plane spin texture in graphene. All the unique features of the studied graphene/In$ _2$ Se$ _3$ heterostructure can be experimentally detected, offering a promising approach for developing advanced spintronic devices with enhanced performance and efficiency.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages, 7 figures
Ultra-low-resistivity nitrogen-doped p-type Cu2O thin films fabricated by reactive HiPIMS
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
Jiří Rezek, Jan Koloros, Jiří Houška, Radomír Čerstvý, Stanislav Haviar, Jemal Yimer Damte, David Kolenatý, Pavel Baroch
We have successfully fabricated the nitrogen-doped cuprous oxide thin films on the amorphous standard soda-lime glass by reactive high-power impulse magnetron sputtering. The energy of film-forming particles was controlled by the value of pulse-averaged target power density, which has a significant impact on the elemental composition, structure and optoelectrical properties of the films. We have shown that the high-energy regime is more suitable for preserving Cu2O structure and leads to continuous substitution of oxygen by nitrogen compared with the low-energy regime. Moreover, in the high-energy regime, it is possible, to some extent, to independently control the electrical resistivity and optical properties. The electrical resistivity decreases down to 5 x10-2 this http URL at the optical band gap 2.0-2.3 eV. Special attention is paid to the formation of nitrogen molecules and their ability to form shallow acceptor states. Experimental results supported by our DFT calculations indicate that N2 replacing Cu in the Cu2O lattice is one possible (but not the only possible) acceptor. We have also found that the formation of nitrogen molecules is preferred in a high-energy regime.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
Anomalous energy correlations and spectral form factor in the nonergodic phase of the $β$-ensemble
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-06-19 20:00 EDT
Basudha Roy, Adway Kumar Das, Anandamohan Ghosh, Ivan M. Khaymovich
The $ \beta$ -ensemble is a prototypical model of a single particle system on a one-dimensional disordered lattice with inhomogeneous nearest neighbor hopping. Corresponding nonergodic phase has an anomalous critical energy scale, $ E_c$ : correlations are present above and absent below $ E_c$ as reflected in the number variance. We study the dynamical properties of the $ \beta$ -ensemble where the critical energy controls the characteristic timescales. In particular, the spectral form factor equilibrates at a relaxation time, $ t_\mathrm{R} \equiv E_c^{-1}$ , which is parametrically smaller than the Heisenberg time, $ t_\mathrm{H}$ , given by the inverse of the mean level spacing. Incidentally, the dimensionless relaxation time, $ \tau_\mathrm{R} \equiv t_\mathrm{R}/t_\mathrm{H} \ll 1$ is equal to the Dyson index, $ \beta$ . We show that the energy correlations are absent within a temporal window $ t_\mathrm{R} < t < t_\mathrm{H}$ , which we term as the correlation void. This is in contrast to the mechanism of equilibration in a typical many-body system. We analytically explain the qualitative behavior of the number variance and the spectral form factor of the $ \beta$ -ensemble by a spatially local mapping to the Anderson model.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Other Condensed Matter (cond-mat.other), Quantum Physics (quant-ph)
11 pages, 8 figures
Highly anisotropic magnetic phase diagram of the ferromagnetic rare-earth diboride HoB$_{2}$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-19 20:00 EDT
Takafumi D. Yamamoto, Hiroyuki Takeya, Kensei Terashima, Akiko T. Saito, Yoshihiko Takano
Rare-earth (RE) compounds have been of enormous interest in condensed matter physics as a platform for the exploration of interesting physical phenomena. Here, we report the successful single crystal growth of HoB$ _{2}$ , which exhibits a paramagnetic (PM)-ferromagnetic (FM) phase transition at 15 K and another phase transition at 11 K, and the discovery of a highly anisotropic magnetic phase diagram of this FM diboride. Magnetization measurements suggest that the ferromagnetically ordered moments of Ho$ ^{3+}$ ions are oriented at a direction tilted by 50 degrees from the ab-plane at 2K, which rotate largely toward the ab-plane direction upon application of a magnetic field, but hardly toward the c-axis direction. Heat capacity and electrical resistivity measurements clearly demonstrate that the low-temperature phase transition at 11 K occurs even under high magnetic fields along the ab-plane direction, whereas it disappears immediately by magnetic fields along the c-axis direction. Moreover, the field-induced crossover phenomenon between FM and PM phases near 15 K is found to be more promoted when applying a magnetic field along the ab-plane direction. The resulting magnetic phase diagram reveals that in-plane magnetic anisotropy is predominant in the present system, which contradicts the previous report of a spin reorientation phenomenon toward the c-axis direction between 11 K and 15 K. Taken together, the present findings suggest the presence of strong competition between in-plane and out-of-plane magnetic anisotropies in HoB$ _{2}$ , giving rise to the unique FM spin arrangement.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Strain-tuning for superconductivity in La$_3$Ni$_2$O$_7$ thin films
New Submission | Superconductivity (cond-mat.supr-con) | 2025-06-19 20:00 EDT
Motoki Osada, Chieko Terakura, Akiko Kikkawa, Masamichi Nakajima, Hsiao-Yi Chen, Yusuke Nomura, Yoshinori Tokura, Atsushi Tsukazaki
The recent discovery of high-transition temperature ($ T_\mathrm{c}$ ) superconductivity in pressurized La$ {3}$ Ni$ {2}$ O$ {7}$ bulk crystals has attracted keen attention due to its characteristic energy diagram of $ e{g}$ orbitals, containing nearly half-filled $ d{3z^2 - r^2}$ and quarter-filled $ d{x^2 - y^2}$ orbitals. This finding provides valuable insights into the orbital contributions and interlayer interactions in double NiO$ {6}$ octahedra, offering opportunities to control the electronic structure via ligand field variations. Here, we demonstrate strain-tuning of $ T\mathrm{c}$ over a range of 50 K in La$ _{3}$ Ni$ _{2}$ O$ {7}$ films grown on different oxide substrates under 20 GPa. As the $ c/a$ ratio increases, the onset $ T\mathrm{c}$ systematically rises from 10 K in the tensile-strained film on SrTiO$ _{3}$ to a maximum of about 60 K in the compressively strained film on LaAlO$ {3}$ . These systematic variations suggest that strain engineering is a promising strategy for expanding superconductivity in bilayer nickelates by tuning the orbital energy landscape toward high-$ T\mathrm{c}$ superconductivity.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
18 pages, 4 figures
Commun. Phys. 8, 251 (2025)
SOT Enabled 3D Magnetic Field Sensor with Low Offset and High Sensitivity
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-19 20:00 EDT
Sebastian Zeilinger, Johannes Güttinger, Klemens Prügl, Michael Kirsch, Joshua M. Salazar-Mejía, Sabri Koraltan, Philip Heinrich, Sophie Zeilinger, Bernd Aichner, Florian Bruckner, Hubert Brückl, Armin Satz, Dieter Suess
In this work we demonstrate a spin-orbit torque (SOT) magnetic field sensor, designed as a Ta/CoFeB/MgO structure, with high sensitivity and capable of active offset compensation in all three spatial directions. This is described and verified in both experiment and simulation. The measurements of magnetic fields showed an offset of 36, 50, and 37$ \mathrm{\mu T}$ for x-, y-, and z-fields. Furthermore, the sensitivities of these measurements had values of 590, 580, and 490$ \mathrm{V,A^{-1},T^{-1}}$ in the x-, y-, and z-direction. In addition, the robustness to bias fields is demonstrated via experiments and single spin simulations by applying bias fields in y-direction. Cross sensitivities were further analyzed via single spin simulations performing a parameter sweep of different bias fields in the y- and z-direction up to $ \pm$ 1mT. Finally, the extraction of the SOT parameters $ \eta_\mathrm{DL}$ and $ \eta_\mathrm{FL}$ is shown via optimization of a single-spin curve to the experimental measurements.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
27 pages, 6 figures. Submitted to Physical Review Applied
High-Entropy Skutterudites as Thermoelectrics: Synthesizability and Band Convergence via the Cocktail Effect
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
Jose J. Plata, Antonio Morales-Altarejos, Elena R. Remesal, Victor Posligua, Antonio M. Márquez
High entropy materials offer a promising avenue for thermoelectric materials discovery, design, and optimization. However, the large chemical spaces that need to be explored hamper their development. In this work, a large family of high-entropy skutterudites is explored as promising thermoelectric materials. Their synthesizability is screened and rationalized using the disordered enthalpy-entropy descriptor through high-throughput density functional theory calculations. In the case of high-entropy skutterudites, the thermodynamic density of states and the entropy gain parameter appear to be key factors for their stabilization. Electronic band structure analyses not only show a reduction in the band gap, which enhances carrier concentration and electrical conductivity, but also a band convergence phenomenon for some specific compositions, which is related to the “cocktail effect”. Analyzing atom-projected band structures shows how band convergence is due to the simultaneous presence of Fe, Ni, and Co in the compound. The presence of Rh or Ir, while not contributing to this band convergence effect, can be directly linked to an increase in system’s entropy, which enhances the thermodynamic stability of these materials.
Materials Science (cond-mat.mtrl-sci)
15 pages, 4 figures, Supplementary Informarion included at the end
Supercurrent modulation in InSb nanoflag-based Josephson junctions by scanning gate microscopy
New Submission | Superconductivity (cond-mat.supr-con) | 2025-06-19 20:00 EDT
Antonio Lombardi, Gaurav Shukla, Giada Bucci, Sedighe Salimian, Valentina Zannier, Simone Traverso, Samuele Fracassi, Niccolo Traverso Ziani, Maura Sassetti, Matteo Carrega, Fabio Beltram, Lucia Sorba, Stefan Heun
InSb nanoflags represent an interesting platform for quantum transport and have recently been exploited in the study of hybrid planar Josephson junctions. Due to the uncovered semiconductor surface, they are also good candidates for surface probe techniques. Here, we report the first Scanning Gate Microscopy (SGM) experiments on Nb-contacted InSb nanoflag-based Josephson junctions. In the normal state, sizable conductance modulation via the charged tip of the SGM is recorded. In the superconducting state, we report the first application of Scanning Gate Microscopy to superconducting weak links, demonstrating the possibility of manipulating the supercurrent flow across a semiconductor-superconductor heterostructure at a local level. The experimental findings are consistent with theoretical predictions and establish a new way of investigating the behavior of superconducting weak links, towards the local imaging of supercurrent flow.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Microgravity-assisted off-axis spin vortex in a $^{87}$Rb dipolar spinor Bose-Einstein condensate
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-06-19 20:00 EDT
The generation of the ground state of a spin vortex in a $ ^{87}$ Rb Bose-Einstein condensate with the assistance of an optical plug has been studied. However, gravity is everywhere, and this potential linear dependence on the spatial position will destroy the axisymmetric structure of the system with the optical plug. In this case, the question of whether the spin vortex ground state still exists remains unresolved. The present study aims to explore the impact of microgravity on the formation of the spin vortex state with the assistance of an optical plug. To this end, a simple model has been employed to provide a comprehensive understanding of the phenomenon. The Gross-Pitaevskii equations are solved by setting the optical plug intensity, adjusting the optical plug width, and adjusting the microgravity strength. This process results in the phase diagram for the single-mode state and spin vortex state. Under microgravity situations, we observe an off-axis structure of the spin vortex state. Our calculations offer a reliable approach to generating spin vortex states in a microgravity environment.
Quantum Gases (cond-mat.quant-gas), Atomic Physics (physics.atom-ph)
Successive Phase Transitions in the Quasi-Kagome Lattice System URhSn Studied by Resonant X-ray Scattering
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-19 20:00 EDT
Chihiro Tabata, Fusako Kon, Ruo Hibino, Yusei Shimizu, Hiroshi Amitsuka, Koji Kaneko, Yoshiya Homma, Dai Aoki, Hironori Nakao
Successive phase transitions in the quasi-kagome compound URhSn were investigated by resonant X-ray scattering (RXS) at the uranium $ M_4$ edge. In the high-temperature phase between 16 K and 54 K, an additional RXS signal was detected superposed onto fundamental reflections in both $ \pi$ -$ \sigma’$ and $ \pi$ -$ \pi’$ polarization channels. Upon cooling below 16 K, reported as a ferromagnetic phase along $ c$ , substantial enhancements were observed again in the both polarization channels at the 300 reflection, demonstrating a simultaneous emergence of in-plane spin alongside the $ c$ -axis ferromagnetic components. The observed behavior can be interpreted by an antiferro-quadrupole (AFQ) order of $ O_{yz}$ or $ O_{zx}$ characterized by a propagation vector $ q = 0$ in the intermediate phase, which then coexists with a ferromagnetic component below 16 K. The resulting ground state structure breaks the mirror symmetry perpendicular to the kagome plane, identifying the formation of a unique AFQ order with either chirality or polarity in URhSn.
Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 5 figures
The maximum-average subtensor problem: equilibrium and out-of-equilibrium properties
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-06-19 20:00 EDT
Vittorio Erba, Nathan Malo Kupferschmid, Rodrigo Pérez Ortiz, Lenka Zdeborová
In this paper we introduce and study the Maximum-Average Subtensor ($ p$ -MAS) problem, in which one wants to find a subtensor of size $ k$ of a given random tensor of size $ N$ , both of order $ p$ , with maximum sum of entries. We are motivated by recent work on the matrix case of the problem in which several equilibrium and non-equilibrium properties have been characterized analytically in the asymptotic regime $ 1 \ll k \ll N$ , and a puzzling phenomenon was observed involving the coexistence of a clustered equilibrium phase and an efficient algorithm which produces submatrices in this phase. Here we extend previous results on equilibrium and algorithmic properties for the matrix case to the tensor case. We show that the tensor case has a similar equilibrium phase diagram as the matrix case, and an overall similar phenomenology for the considered algorithms. Additionally, we consider out-of-equilibrium landscape properties using Overlap Gap Properties and Franz-Parisi analysis, and discuss the implications or lack-thereof for average-case algorithmic hardness.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Information Theory (cs.IT), Probability (math.PR)
Towards High-Efficiency Solar Cells: Insights into AsNCa 3 Antiperovskite as Active Layer
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
M. Irfan, B. D. Aparicio-Huacarpuma, C. M. de Oliveira Bastos, M. J. Piotrowski, C. R. C. Rêgo, D. Guedes-Sobrinho, R. Besse, A. M. Almeida Silva, Alexandre C. Dias, L. A. Ribeiro Jr
Advances in photovoltaic technology are a viable route to contribute to cleaner and more sustainable energy solutions, placing perovskite-based materials among the best candidates for solar energy conversion. However, some challenges must be addressed to enhance their performance and stability. Herein, we report an investigation of the AsNCa3 antiperovskite system for its potential in photovoltaic devices. We consider eight distinct crystalline phases, their structural parameters, dynamical stability, and electronic and optical properties. Furthermore, we consider each structural phase’s contributions to solar harvesting efficiency by calculating the power conversion efficiency (PCE) using the spectroscopiclimited maximum efficiency (SLME) formalism, which in this case reaches a maximum of 31.2%. All dynamically stable phases exhibit a band gap around 1.3 eV, which lies within the optimal range for single-junction solar cells and yields PCE values comparable to the theoretical maximum PCE for silicon. These results place AsNCa3 antiperovskites as promising candidates for high-efficiency photovoltaic applications. Notably, the PCE is only slightly changed by structural phase modification, suggesting that phase transitions induced by environmental conditions during device operation might not compromise device performance.
Materials Science (cond-mat.mtrl-sci)
Devitrification and Melting Dynamics in Vapor Deposited Water Ice
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-19 20:00 EDT
Fabio Leoni, Fausto Martelli, John Russo
The equilibration dynamics of ultrastable glasses subjected to heating protocols has attracted recent experimental and theoretical interest. With simulations of the mW water model, we investigate the devitrification and melting dynamics of both conventional quenched (QG) and vapor deposited (DG) amorphous ices under controlled heating ramps. By developing an algorithm to reconstruct hydrogen-bond networks, we show that bond ring statistics correlates with the structural stability of the glasses and allows tracking crystalline and liquid clusters during devitrification and melting. We find that QG melts in the bulk, whereas melting in DG preferentially begins near the free surface. During devitrification, the DG shows an excess of 5-membered rings near the free surface, which is consistent with its tendency to nucleate the crystal phase in this region. Additionally, the DG shows an Avrami exponent exceeding the standard 1+d behavior, while both glasses display the same sub-3d growth of liquid clusters across heating rates, indicating that the DG enhanced exponent stems from its higher kinetic stability.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci)
Generalized Onsager reciprocal relations of charge and spin transport
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-06-19 20:00 EDT
Guan-Hua Huang, Hui Tang, Shizhong Zhang, Zhongbo Yan, Zhigang Wu
In spin-orbit-coupled systems the charge and spin transport are generally coupled to each other, namely a charge current will induce a spin current and vice versa. In the presence of time-reversal symmetry $ \mathcal{T}$ , the cross-coupling transport coefficients describing how one process affects the other are constrained by the famous Onsager reciprocal relations. In this paper, we generalize the Onsager reciprocal relations of charge and spin transport to systems that break the time-reversal symmetry but preserve a combined symmetry of $ \mathcal{T}$ and some other symmetry operation $ \mathcal{O}$ . We show that the symmetry or antisymmetry of the cross-coupling transport coefficients remains in place provided that the operator $ \mathcal{O}$ meets certain conditions. Among many candidate systems where our generalized Onsager relations apply, we focus on a conceptually simple and experimentally realized model in cold atomic systems for explicit demonstration and use these relations to predict highly non-trivial transport phenomena that can be readily verified experimentally.
Quantum Gases (cond-mat.quant-gas), Statistical Mechanics (cond-mat.stat-mech), Strongly Correlated Electrons (cond-mat.str-el)
Solitonic Andreev Spin Qubit
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-19 20:00 EDT
We propose a novel type of superconducting spin qubit, dubbed solitonic Andreev spin qubit (SASQ), that combines features of Andreev spin qubits and geometric spin qubits. The two SASQ states are the degenerate spin orientations of an Andreev bound state trapped in a circular Josephson junction with a Corbino disk geometry, created on a 2DEG. The junction is subjected to a weak magnetic flux that induces a fluxoid mismatch between the inner disk and outer ring superconductors. The fluxoid mismatch produces a cancellation of the induced pairing that traps unconventional spin-degenerate Andreev bound states analogous to Jackiw-Rebbi solitons. They are localized at a position around the junction that can be controlled by changing the superconducting phase difference. Moving a soliton with a phase bias induces a holonomic rotation of its spin, by virtue of the spin-orbit coupling in the 2DEG. The holonomic qubit trajectories can densely cover the full Bloch sphere as the soliton revolves around the junction. Effects of non-holonomic (dynamic) qubit drift are also analyzed.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
6 pages, 4 figures
A new angle on stacking faults: Breaking the edge-on limit in high-resolution defect analysis
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
Nicolas Karpstein, Lukas Müller, Andreas Bezold, Steffen Neumeier, Erdmann Spiecker
The nature of stacking faults - whether intrinsic or extrinsic - plays a pivotal role in defect-mediated processes in crystalline materials. Yet, current electron microscopy techniques for their reliable analysis remain limited to either conventional fringe-contrast imaging of inclined faults or atomic-resolution imaging of edge-on configurations. Here, we overcome this dichotomy by introducing a high-resolution scanning transmission electron microscopy (HRSTEM) method that enables full structural discrimination of inclined stacking faults in fcc and $ L1_2$ crystals. This approach eliminates a long-standing geometric constraint on high-resolution analysis, providing comprehensive access to stacking faults on all glide planes along the widely used [001] and [110] zone axes. We demonstrate the robustness of the method in a CoNi-based superalloy, achieving clear discrimination of fault types even in overlapping configurations and foil thicknesses exceeding 100 nm. Simulations reveal that fault-induced de-channeling is key to contrast formation and is strongly governed by the fault’s depth within the sample. Leveraging this effect, we further establish a route to artificially generate ultrathin TEM lamellae - bounded by the stacking fault itself - thereby enhancing contrast for atomic-scale studies of long-range ordering, compositional fluctuations, and nanoclustering.
Materials Science (cond-mat.mtrl-sci)
42 pages, 8 figures, 11 supplementary figures
Unconventional Spin Dynamics and Supersolid Excitations in the Triangular-Lattice XXZ Model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-19 20:00 EDT
Rafael Flores-Calderón, Roderich Moessner, Frank Pollmann
Motivated by recent experiments, we investigate the spin-1/2 XXZ model on the triangular lattice with strong Ising anisotropy, combining large-scale numerical simulations and analytical methods to uncover unconventional spin dynamics. First, we compute the dynamical spin structure factor using density matrix renormalization group (DMRG) simulations and find excellent agreement with inelastic neutron scattering data on the layered compound $ \text{K}_2\text{Co}(\text{SeO}_3)_2$ . The low-energy spectrum reveals a roton-like minimum at the $ M$ point, absent in linear spin-wave theory, accompanied by peak intensity and a broad continuum above it. Near the $ \Gamma$ point, we observe an approximately linear dispersion with vanishing spectral weight. Second, we compare two analytical frameworks that reproduce the observed features. The first is a hard-core boson approach, which includes: (i) an effective staggered boson model (ESBM) at zero magnetic field, (ii) perturbation theory applied to the one-third magnetization plateau, and (iii) a self-consistent mean-field Schwinger boson theory (SBT). The second framework is based on a variational supersolid quantum dimer model (QDM) ansatz, combined with a single-mode approximation. The SBT captures the broad continuum, the $ M$ -point minimum, and linear dispersion at $ \Gamma$ , whereas the QDM reproduces the roton minimum and linear dispersion at finite momentum near $ \Gamma$ . Remarkably, both the QDM wavefunction and the DMRG ground state exhibit nearly identical structure factors with pronounced transverse photon-like excitations. Together, our comprehensive theoretical and numerical analysis elucidates the microscopic origin of supersolid excitations in the XXZ triangular lattice model and their proximity to a spin liquid phase observed experimentally.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech)
Intertwined magnetic phase driven exchange bias and its impact on the anomalous Hall effect in MnBi$_4$Te$_7$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-19 20:00 EDT
Nazma Firdosh, Shreyashi Sinha, Indraneel Sinha, Mainpal Singh, Satyabrata Patnaik, Sujit Manna
We report on the interplay between atomic scale inhomogeneity and competing magnetic phases and its effect on the anomalous Hall effect in the layered antiferromagnet MnBi$ _4$ Te$ _7$ , a natural superlattice hosting coexisting ferromagnetic and antiferromagnetic phases. Using a combination of scanning tunneling microscopy (STM), DC and AC magnetization, and magneto-transport measurements, we reveal that intrinsic Mn Bi antisite defects induce strong interlayer exchange coupling, giving rise to a robust exchange bias observed in both magnetic and Hall responses. The exchange bias undergoes a transition from asymmetric to symmetric behavior between 2 K and 6 K, indicating a temperature driven dynamical reconfiguration of interfacial spin structures. The training effect analysis revealed a stronger contribution of frozen spins at 2 K compared to 6 K, with relaxation amplitude shift from -264 Oe to 306 Oe. This sign reversal indicates a field-induced change in interfacial coupling. The temperature dependence of longitudinal resistivity and magnetization reveals complementary behavior, indicating the coexistence of two distinct spin states near the magnetic transition temperature. The phase fraction based resistivity model captures the distinct scattering mechanisms that govern electronic transport across different magnetic regimes. Our findings offer a direct link between microscopic disorder, interfacial magnetism and macroscopic topological phenomena in magnetic topological insulators.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
11 pages and 5 figures
Theory of universal Planckian metal in t-J model: application for high-Tc cuprate superconductors
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-19 20:00 EDT
Yung-Yeh Chang, Khoe Van Nguyen, Kimberly Remund, Chung-Hou Chung
The mysterious quantum-critical Planckian bad metal phase with perfect T-linear resistivity persisting beyond the quasi-particle limit and universal T-linear scattering rate has been observed in various high-Tc cuprate superconductors. Here, we develop a realistic theoretical approach to this phase in an analytically solvable large-N multi-channel Kondo lattice model, derived from a heavy-fermion formulated conventionaL t-J model, known for qualitatively describing cuprates. This phase is originated from critical charge Kondo fluctuations where disordered local bosonic charge fluctuations couple to spinon and heavy conduction-electron Fermi surfaces near a charge-Kondo-breakdown local quantum critical point associated with pseudogap-to-Fermi liquid transition. Our results show excellent agreement with experiments and offer broad implications for other unconventional superconductors.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
31 pagesw, 3 figures
The study of electronic, structural, mechanical, and piezoelectric properties of bulk NbOX2 (X = Cl, Br, and I) using density functional theory
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
L. D. Tamang, B. Chettri, L. Celestine, R. Zosiamliana, S. Gurung, A. Laref, Shalika R. Bhandari, Tatyana Orlova, D. P. Rai
In this work, we have performed a comprehensive study of dielectric materials NbOX2 (X=Cl, Br, and I) within the framework of density functional theory, incorporating both conventional and hybrid this http URL studies focus on the structure, electronic, elastic, and piezoelectric properties. Piezoelectricity is an innovative avenue to extract energy by manipulating the material’s structures via mechanical stress. The use of non-lead-based material for piezoelectricity added an advantage of a greener approach. Among the investigated materials, bulk NbOI2 exhibits the highest piezoelectric response of 6.32 C/m$ ^2$ , which is around 31% higher than NbOCl2, NbOBr2 and even lead zirconate titanate.
Materials Science (cond-mat.mtrl-sci)
Quantum metric and localization in a quasicrystal
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-06-19 20:00 EDT
Quentin Marsal, Patric Holmvall, Annica M. Black-Schaffer
We use the quantum metric to understand the properties of quasicrystals, represented by the one-dimensional (1D) Fibonacci chain. We show that the quantum metric can relate the localization properties of the eigenstates to the scale-invariance of both the chain and its energy spectrum. In particular, the quantum metric incorporates information about distances between the local symmetry centers of each eigenstate, making it much more sensitive to the localization properties of quasicrystals than other measures of localization, such as the inverse participation ratio. We further find that a full description of localization requires us to introduce a new phasonic component to the quantum metric, and a mixed phason-position Chern number. Finally, we show that the sum of both position and phasonic components of the quantum metric is lower-bounded by the gap labels associated with each energy gap of the Fibonacci chain. This establishes a direct link between the spatial localization and fractal energy spectrum of quasicrystals. Taken together, the quantum metric provides a unifying, yet accessible, understanding of quasicrystals, rooted in their scale-invariance and with intriguing consequences also for many-body physics.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
12 pages including supplementary, 6 figures
Advanced Langevin thermostats: Properties, extensions to rheology, and a lean momentum-conserving approach
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-19 20:00 EDT
Shubham Agarwal, Sergey V. Sukhomlinov, Marc Honecker, Martin H. Müser
The Langevin equation accounts for unresolved bath degrees of freedom driving the system toward the bath temperature. Because of this, numerical solutions of the Langevin equation have a long history. Here, we recapitulate, combine, and extend existing Langevin-equation based thermostats, scrutinize their properties and demonstrate their superiority over global kinetic-energy controls. Our work includes compact, asymptotic-analysis based derivations of stochastic thermostats, including the highly accurate Grønbech-Jensen scheme. Proposed extensions include a precise, colored and a lean, momentum-conserving thermostat.
Statistical Mechanics (cond-mat.stat-mech), Materials Science (cond-mat.mtrl-sci), Soft Condensed Matter (cond-mat.soft)
18 pages, 10 figures, 43 references
Learning to flock in open space by avoiding collisions and staying together
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-19 20:00 EDT
Martino Brambati, Antonio Celani, Marco Gherardi, Francesco Ginelli
We investigate the emergence of cohesive flocking in open, boundless space using a multi-agent reinforcement learning framework. Agents integrate positional and orientational information from their closest topological neighbours and learn to balance alignment and attractive interactions by optimizing a local cost function that penalizes both excessive separation and close-range crowding. The resulting Vicsek-like dynamics is robust to algorithmic implementation details and yields cohesive collective motion with high polar order. The optimal policy is dominated by strong aligning interactions when agents are sufficiently close to their neighbours, and a flexible combination of alignment and attraction at larger separations. We further characterize the internal structure and dynamics of the resulting groups using liquid-state metrics and neighbour exchange rates, finding qualitative agreement with empirical observations in starling flocks. These results suggest that flocking may emerge in groups of moving agents as an adaptive response to the biological imperatives of staying together while avoiding collisions.
Soft Condensed Matter (cond-mat.soft)
13 pages + appendices
Revealing the Breakdown Mechanism and Heat Dissipation in Few-Layered semimetallic PtSe2
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
Bubunu Biswal, Abinash Tripathy, Renu Yadav, Abhishek Misra
Platinum diselenide (PtSe2) is an emerging two-dimensional (2D) transition metal dichalcogenide known for its excellent electrical and optical properties, along with remarkable air stability. For PtSe2-based electronic devices, understanding high-field breakdown and heat dissipation is crucial for designing high-performance and energy-efficient systems operating under extreme conditions. In this work, we investigate the breakdown mechanisms of semimetallic PtSe2 at both low and room temperatures. Heat dissipation is quantified via interfacial thermal conductivity (ITC) of PtSe2/SiO2 and PtSe2/h-BN interfaces using Raman thermometry. Our findings indicate that at room temperature, device breakdown is predominantly governed by self-heating effects. Conversely, at low temperatures, the breakdown is mainly driven by carrier multiplication under high electric fields, as further confirmed by Hall measurements.
Materials Science (cond-mat.mtrl-sci)
10 pages, 4 figures
Maximizing solubility in rock salt high-entropy oxides
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
Matthew Furst, Joseph Petruska, Dhiya Srikanth, Jacob T. Sivak, Susan B. Sinnott, Christina M. Rost, Jon-Paul Maria, Saeed S. I. Almishal
To explore and quantitatively map the cation-size mismatch solubility limits in high-entropy oxides (HEOs), we report on Ca$ ^{2+}$ substitution in prototypical MgCoNiCuZnO, because, while isovalent, Ca$ ^{2+}$ is 38% larger than its partners’ average ionic radii. Using the thermodynamics-grounded bond-length distribution descriptor, we identify Ca$ ^{2+}$ -Cu$ ^{2+}$ interactions as the primary prospective lattice destabilizer. Bulk synthesis confirms only 4% Ca solubility with Cu at 950$ ^o$ C, modestly rising to 5% after Cu removal at 1150$ ^o$ C. We then employ far-from-equilibrium pulsed-laser deposition to investigate metastable solubility: epitaxial films incorporate 10% Ca with Cu and a full 20% Ca without, doubling and quadrupling the respective bulk limits. This Ca uptake additionally enables deterministic lattice-parameter control via Ca concentration. Overall, our results demonstrate both the extended solubility possible in HEO systems, particularly when accessing metastable states through quenching from high-energy plasma, and that the specific constellation of solid-solvent cations can be rationally engineered to minimize bond-length distributions when largely misfit cations are added, thus expanding the accessible compositional space.
Materials Science (cond-mat.mtrl-sci)
Determining the chemical potential via universal density functional learning
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-19 20:00 EDT
Florian Sammüller, Matthias Schmidt
We demonstrate that the machine learning of density functionals allows one to determine simultaneously the equilibrium chemical potential across simulation datasets of inhomogeneous classical fluids. Minimization of an implicit loss function based on an Euler-Lagrange equation yields both the universal one-body direct correlation functional, which is represented locally by a neural network, as well as the system-specific unknown chemical potential values. The method can serve as an efficient alternative to conventional computational techniques of measuring the chemical potential. It also facilitates using canonical training data from Brownian dynamics, molecular dynamics, or Monte Carlo simulations as a basis for constructing neural density functionals, which are fit for accurate multiscale prediction of soft matter systems in equilibrium.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
8 pages, 5 figures
Duplication-divergence growing graph models
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-19 20:00 EDT
In recent decades, it has been emphasized that the evolving structure of networks may be shaped by interaction principles that yield sparse graphs with a vertex degree distribution exhibiting an algebraic tail, and other structural traits that are not featured in traditional random graphs. In this respect, through a mean-field approach, this review tackles the statistical physics of graph models based on the interaction principle of duplication-divergence. Additional sophistications extending the duplication-divergence model are also reviewed as well as generalizations of other known models. Possible research gaps and related prior results are then discussed.
Statistical Mechanics (cond-mat.stat-mech), Adaptation and Self-Organizing Systems (nlin.AO), Physics and Society (physics.soc-ph), Molecular Networks (q-bio.MN)
45 pages, 5 figures, 1 table, review article (1st vers.)
Flips Reveal the Universal Impact of Memory on Random Explorations
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-19 20:00 EDT
Julien Brémont, Léo Régnier, Alex Barbier–Chebbah, Olivier Bénichou, Raphaël Voituriez
Quantifying space exploration is a central question in random walk theory, with direct applications ranging from animal foraging, diffusion-limited reactions, and intracellular transport to stock markets. In particular, the explored domain by one or many simple memoryless (or Markovian) random walks has received considerable attention . However, the physical systems mentioned above typically involve significant memory effects, and so far, no general framework exists to analyze such systems. We introduce the concept of a \emph{flip}, defined most naturally in one dimension, where the visited territory is $ [x_{\rm min}, x_{\rm max}]$ : a flip occurs when, after discovering a new site at $ x_{\rm max}$ , the walker next discovers $ x_{\rm min} - 1$ instead of $ x_{\rm max} + 1$ (and vice-versa).
While it reduces to the classical splitting probability in Markovian systems, we show that the flip probability serves as a key observable for quantifying the impact of memory effects on space exploration.
Here, we demonstrate that the flip probability follows a strikingly simple and universal law: it decays inversely with the number of sites visited, as (1/n), independently of the underlying stochastic process. We confirm this behavior through simulations across paradigmatic non-Markovian models and observe it in real-world systems, without relying on model assumptions, including biological tracer motion, DNA sequences, and financial market dynamics. Finally, we reveal the physical mechanism behind this universality and show how it extends to higher-dimensional and fractal domains. Our determination of universal flip statistics lay the groundwork for understanding how memory effects govern random explorations.
Statistical Mechanics (cond-mat.stat-mech)
A Machine Learning Framework for Modeling Ensemble Properties of Atomically Disordered Materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-06-19 20:00 EDT
Zhenyao Fang, Ting-Wei Hsu, Qimin Yan
Disorder, though naturally present in experimental samples and strongly influencing a wide range of material phenomena, remains underexplored in first-principles studies due to the computational cost of sampling the large supercell and configurational space. The recent development of machine learning techniques, particularly graph neural networks (GNNs), has enabled the efficient and accurate predictions of complex material properties, offering promising tools for studying disordered systems. In this work, we introduce a computational framework that integrates GNNs with Monte Carlo simulations for efficient calculations of thermodynamic properties and ensemble-averaged functional properties of disordered materials. Using the surface-termination-disordered MXene monolayer \ch{Ti3C2T}$ _{2-x}$ as a representative system, we investigate the effect of surface termination disorder involving \ch{-F}, \ch{-O}, and termination vacancies on the electrical and optical conductivity spectra. We find that surface termination disorder affects the temperature dependence of electrical conductivity, inducing a peak close to the order-disorder phase transition temperature that reflects the competition between scattering and electron filling effects of the surface termination groups across the phase transition. In contrast, optical conductivity remains robust to local disorder across a wide temperature range and is governed primarily by the global chemical composition of surface terminations. These results demonstrate the utility of our machine-learning-assisted framework for statistically modeling disorder effects and ensemble properties in complex materials, opening new avenues for future studies of disorder-driven phenomena in systems such as high-entropy alloys and disordered magnetic compounds.
Materials Science (cond-mat.mtrl-sci)
Fokker-Planck Score Learning: Efficient Free-Energy Estimation under Periodic Boundary Conditions
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-06-19 20:00 EDT
Accurate free-energy estimation is essential in molecular simulation, yet the periodic boundary conditions (PBC) commonly used in computer simulations have rarely been explicitly exploited. Equilibrium methods such as umbrella sampling, metadynamics, and adaptive biasing force require extensive sampling, while non-equilibrium pulling with Jarzynski’s equality suffers from poor convergence due to exponential averaging. Here, we introduce a physics-informed, score-based diffusion framework: by mapping PBC simulations onto a Brownian particle in a periodic potential, we derive the Fokker-Planck steady-state score that directly encodes free-energy gradients. A neural network is trained on non-equilibrium trajectories to learn this score, providing a principled scheme to efficiently reconstruct the potential of mean force (PMF). On benchmark periodic potentials and small-molecule membrane permeation, our method is up to one order of magnitude more efficient than umbrella sampling.
Statistical Mechanics (cond-mat.stat-mech), Chemical Physics (physics.chem-ph)
11 pages, 4 figures
Machine learning based prediction of dynamical clustering in granular gases
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-06-19 20:00 EDT
Sai Preetham Sata, Ralf Stannarius, Benjamin Noack, Dmitry Puzyrev
When dense granular gases are continuously excited under microgravity conditions, spatial inhomogeneities of the particle number density can emerge. A significant share of particles may collect in strongly overpopulated regions, called clusters. This dynamical clustering, or gas-cluster transition, is caused by a complex interplay and balance between the energy influx and dissipation in particle collisions. Particle number density, container geometry, and excitation strength influence this transition. We perform Discrete Element Method (DEM) simulations for ensembles of frictional spheres in a cuboid container and apply the Kolmogorov Smirnov test and a caging criterion to the local packing fraction profiles to detect clusters. Machine learning can be used to study the gas-cluster transition, and can be a promising alternative to identify the state of the system for a given set of system parameters without time-consuming complex DEM simulations. We test various machine learning models and identify the best models to predict dynamical clustering of frictional spheres in a specific experimental geometry.
Soft Condensed Matter (cond-mat.soft), Computational Physics (physics.comp-ph), Data Analysis, Statistics and Probability (physics.data-an), Applications (stat.AP)
32 pages, 35 figures
Anisotropic Josephson coupling of d-vectors arising from interplay with frustrated spin textures
New Submission | Superconductivity (cond-mat.supr-con) | 2025-06-19 20:00 EDT
Grayson R. Frazier, Junyi Zhang, Yi Li
We propose a Cooper pair analogue of Dzyaloshinskii-Moriya’s anisotropic coupling for $ d$ -vectors in an inhomogeneous unconventional superconductor, which can arise when itinerant electrons couple to a local exchange field of frustrated spin moments. Using perturbative Green’s function methods, we examine an $ s$ -$ d$ model on a geometrically frustrated lattice with noncollinear spin texture that breaks time-reversal and parity symmetries, leading to spin-triplet pairing correlations. The effective Josephson tunneling in the presence of such an exchange field leads to an anisotropic Josephson coupling between $ d$ -vectors, which prefers a spatially inhomogeneous pairing order. Furthermore, we discuss anomalous vortices arising from the spatially inhomogeneous $ d$ -vector in the absence of a magnetic field for nonunitary triplet pairing order. We also propose a Josephson diode effect in which the diode efficiency is proportional to the spin chirality of the local exchange field. Our results can help understand the experiments in superconducting proximitized Mn$ _3$ Ge and in 4Hb-TaS$ _2$ .
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
Enhanced two-dimensional ferromagnetism in van der Waals $β$-UTe$_3$ monolayers
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-19 20:00 EDT
S. M. Thomas, A. E. Llacsahuanga, W. Simeth, C. S. Kengle, F. Orlandi, D. Khalyavin, P. Manuel, F. Ronning, E. D. Bauer, J. D. Thompson, Jian-Xin Zhu, A. O. Scheie, Yong P. Chen, P. F. S. Rosa
The discovery of local-moment magnetism in van der Waals (vdW) semiconductors down to the single-layer limit has led to a paradigm shift in the understanding of two-dimensional (2D) magnets and unleashed their potential for applications in microelectronic and optoelectronic devices. The incorporation of strong electronic and magnetic correlations in 2D vdW metals remains a sought-after platform not only to enable control of emergent quantum phases, such as superconductivity, but also to achieve more theoretically tractable microscopic models of complex materials. To date, however, there is limited success in the discovery of such metallic vdW platforms, and $ f$ -electron monolayers remain out of reach. Here we demonstrate that the actinide $ \beta$ -UTe$ _3$ can be exfoliated to the monolayer limit. A sizable electronic specific heat coefficient provides the hallmark of strong correlations. Remarkably, $ \beta$ -UTe$ _3$ remains ferromagnetic in the half-unit-cell limit with an enhanced ordering temperature of 35 K, a factor of two larger than its bulk counterpart. Our work establishes $ \beta$ -UTe$ _3$ as a novel materials platform for investigating and modeling correlated behavior in the monolayer limit and opens numerous avenues for quantum control with, e.g., strain engineering.
Strongly Correlated Electrons (cond-mat.str-el)
10 pages, 5 figures, supplemental information included
Kinetic magnetism in the crossover between the square and triangular lattice Fermi-Hubbard models
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-06-19 20:00 EDT
Darren Pereira, Erich J. Mueller
We calculate the spin correlations that result from the motion of a single dopant in the hard-core Fermi-Hubbard model, as the geometry evolves from a square to a triangular lattice. In particular, we consider the square lattice with an additional hopping along one diagonal, whose strength is continuously varied. We use a high-temperature expansion which expresses the partition function as a sum over closed paths taken by the dopant. We sample thousands of diagrams in the space of closed paths using the quantum Monte Carlo approach of Raghavan and Elser [1,2], which is free of finite-size effects and allows us to simulate temperatures as low as $ T \sim 0.3|t|$ , even in cases where there is a sign problem. For the case of a hole dopant, we find a crossover from kinetic ferromagnetism to kinetic antiferromagnetism as the geometry is tuned from square to triangular, which can be observed in current quantum gas microscopes.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Gases (cond-mat.quant-gas), Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
16 pages, 9 figures