Soft Condensed Matter
Coarse-Grained Molecular Dynamics Simulations of Oxidative Aging and Stabilization in Polymer Melts with Primary Antioxidants: Effects of Antioxidant Concentration and Molecular Architecture
Takato Ishida and Emmanuel Richaud
Industrial polymeric materials often rely on antioxidants to achieve long-term reliability. Previous studies have frequently discussed the stabilization effect in the presence of macroscopic additive migration. However, the micro- to meso-scale coupling between
polymer dynamics and antioxidant molecular dynamics remains insufficiently understood. In this study, we extend a
polymer dynamics simulation framework that can account for oxidative aging. We also update the model so that it can explicitly incorporate antioxidant molecules into the simulation. As a result, the framework enables us to quantify how molecular architecture of antioxidants affects oxidation kinetics, which has previously been inferred only indirectly from apparent changes in reaction rates. It also allows us to evaluate the effects of antioxidant concentration and molecular architecture on the spatial heterogeneity of oxidative aging.
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Mesoscale and Nanoscale Physics
Photon counting beyond the rotating-wave approximation
Steven Kim and Fabian Hassler
Open
quantum systems are often described by a Lindblad master equation, which relies on a set of approximations, most importantly the rotating-wave approximation which is only valid for weak damping. In the Lindblad setting, dissipative processes are described through jump operators, distinguishing between absorption and emission of
photons. This enables the simple identification of emitted
photons which provides a straightforward way to obtain the radiation statistics. Outside the rotating-wave limit, the Lindblad approach does not work. Open
quantum systems can then be described by, e.g., the
quantum Langevin equation. However, in this framework the number of emitted
photons is not easily accessible. In this work, we point out how to obtain the
photon counting statistics from a
quantum Langevin equation and provide an expression for the
photon current operator, for arbitrary systems coupled to linear environments. As an example, we employ the method to study the radiation statistics of a damped harmonic oscillator at finite temperature beyond the rotating-wave approximation. We show that even outside the rotating-wave limit, the most important contribution to the radiation statistics can be captured by an effective Lindblad equation, thus extending the range of possible applications of the Lindblad framework.
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Materials Science
Scalable Solar-Blind Imaging Enabled by Single-Crystalline Beta-Ga2O3 Membranes on Silicon Backplanes
Xiang Xu, Hong Huang, Qi Huang et al. (+14 more)
Ultrawide-bandgap
semiconductors are attractive for
solar-blind ultraviolet (UV) detection owing to their intrinsically low noise and high spectral selectivity, yet their deployment in large-area, high-density electronic imaging systems remains limited by a fundamental trade-off between material quality, device speed, and compatibility with high-density planar silicon readout
circuits. Here, we report a membrane-enabled integration platform based on transferable single-crystalline beta-Ga2O3 that overcomes these constraints at the system level. By exploiting the weak interplanar bonding of beta-Ga2O3 (100) plane, we obtain wafer-scale freestanding single-crystalline membranes that enable vertically integrated photodiodes with sub-microsecond, non-persistent photoresponse and high UV-visible rejection. Crucially, we introduce a stitching-based membrane assembly strategy that decouples array resolution from the size of the source single-crystalline substrate, allowing high-resolution photodetector arrays to be integrated onto silicon thin-film-transistor backplanes. The modular assembled active-
matrix UV imaging arrays exhibit uniform
solar-blind response without image lag, in stark contrast to arrays based on amorphous or polycrystalline films. Beyond beta-Ga2O3, this membrane-enabled and stitching-based modular integration strategy provides a general route toward high-speed, high-resolution electronic imaging systems using transferable single-crystalline
semiconductors.
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All authors Xiang Xu, Hong Huang, Qi Huang, Hao Wang, Huaze Zhu, Junwei Cao, Zheng Zhu, Yaqin Ma, Yiyang Xu, Zhongfang Zhang, Yitong Chen, Ke Chen, Tong Jiang, Bowen Zhu, Xiaolong Zhao, Shibing Long, Wei Kong
Materials Science
Low magnetic moment and unconventional magneto-transport in half-Heusler alloy CoVGe
Ravinder Kumar, Jyotiraditya Pandey, Shoaib Akhtar et al. (+4 more)
In the present work, we experimentally realize CoVGe for the first time and investigate its structural,
magnetic, and transport properties, supported by theoretical calculations. The material crystallizes in a cubic structure and exhibits a very low
magnetic moment of 0.13 {\mu}B per formula unit at 5 K. The temperature dependence of electrical resistivity suggests half-metallic behaviour. Magnetoresistance shows a positive, non-saturating linear field dependence at low temperature that gradually weakens with increasing temperature. The combination of low
magnetic moment and unusual magnetotransport behaviour positions CoVGe as a promising platform for exploring
spin-dependent transport in Heusler-based materials.
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All authors Ravinder Kumar, Jyotiraditya Pandey, Shoaib Akhtar, Sachin Majee, Dibyendu Majee, Samik DuttaGupta, Sachin Gupta
Materials Science
Annotated digital image correlation displacement fields from fatigue crack growth experiments
David Melching, Ferdinand Dömling, Florian Paysan et al. (+3 more)
We present a curated
dataset of planar displacement fields from eight fatigue crack growth experiments obtained via full-field digital image correlation (DIC). The
dataset covers multiple aerospace-grade aluminium
alloys, specimen geometries, material orientations, and load configurations, providing a diverse experimental basis for data-driven fracture mechanics research. Crack tip locations are consistently annotated using an iterative correction procedure applied to all measurements, and fracture mechanical descriptors like stress-intensity factors are provided as additional labels. The
dataset comprises 8,794 unique experimentally observed displacement fields and a total of 70,352 supervised samples generated through standardized interpolation and augmentation. DIC data is provided as uniformly interpolated displacement grids at three standardized resolutions 28 x 28, 64 x 64, and 128 x 128 pixels, each available in three
dataset sizes to support scalable use cases ranging from educational applications to high-capacity model development. Accompanying metadata and a Python interface facilitate filtering, loading, and integration into reproducible machine learning and fracture mechanics workflows.
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All authors David Melching, Ferdinand Dömling, Florian Paysan, Erik Schultheis, Eric Dietrich, Eric Breitbarth
Materials Science
Two-Scale Analysis of the Electrostatics of Dielectric Crystals: Emergence of Polarization Density and Boundary Charges
Shoham Sen, Yang Wang, Timothy Breitzman et al. (+1 more)
Ionic
crystals, such as solid electrolytes and complex
oxides, are central to modern technologies for energy storage, sensing, actuation, and other functional applications. An important fundamental issue in the atomic and
quantum-scale modeling of these materials is defining the macroscopic polarization. In a periodic
crystal, the usual definition of the polarization as the first moment of the charge density in a unit
cell is found to depend qualitatively - allowing even a change in the sign - and quantitatively on the choice of unit
cell. We examine this issue using a rigorous approach based on the framework of 2-scale convergence. By examining the continuum limit of when the
lattice spacing is much smaller than the characteristic dimensions of the body, we show that the 2-scale limit provides both a bulk polarization as well as a surface charge density supported on the boundary of the body. Further, different choices of the periodic unit
cell of the body lead to correspondingly different partial unit
cells at the boundary; these choices give to different bulk polarization and surface charges but compensate such that the electric field and energy are independent of the choice of unit
cell.
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All authors Shoham Sen, Yang Wang, Timothy Breitzman, Kaushik Dayal
Disordered Systems and Neural Networks · Cross-listed from hep-lat
Dirac mode localization in QCD near the crossover temperature
Matteo Giordano, Tamas G. Kovacs and Ferenc Pittler
We study the localization properties of the low-lying Dirac eigenmodes in QCD near the crossover temperature, using stout-smeared staggered
fermions and Symanzik-improved gauge action on the
lattice. On $N_{\mathrm{t}}=8$
lattices we find that localized low modes, absent at low temperature, appear at a temperature $T_{\mathrm{loc}}$ in the range $150\,\mathrm{MeV}\le T_{\mathrm{loc}}\le 160\,\mathrm{MeV}$, well within the
chiral crossover range as determined from the
chiral condensate and from the light-
quark susceptibility. Since with our choice of
lattice action neither the
chiral transition region nor the renormalized mobility edges change significantly above $N_{\mathrm{t}}=8$, our conclusion that $T_{\mathrm{loc}}$ is in the
chiral crossover region is expected to remain valid in the continuum limit.
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Materials Science
Staggered Dzyaloshinskii-Moriya and canting angle in centrosymmetric altermagnetic and ferromagnetic phases: influence on the anomalous Hall effect and Weyl points
Mathews Benny, Xujia Gong, Kamil Jamroszczyk et al. (+5 more)
We present a simple methodology to compute the anomalous
Hall conductivity (AHC) as a function of the canting angles in ferromagnets and altermagnets, starting from a nonmagnetic
Hamiltonian obtained from first-principles calculations that preserves the full
symmetry of the
crystal structure. Magnetism is introduced by including on-site
spin splitting,
spin-orbit coupling, and
spin-canting angles. As a representative material, we study SrRuO$_3$, which supports
spin canting and exhibits a sign change of the AHC. In the
ferromagnetic phase, the low-energy AHC is found to be close to zero at the
Fermi level, in agreement with experimental observations. We show that the dependence of the AHC on the relevant physical parameters is most pronounced in the central region of the electronic bandwidth. We determine the
symmetry-allowed components of the AHC for different
magnetic orders in the large family of transition-metal perovskite ABO$_3$ compounds with space group $62$, including the spontaneous in-plane anomalous
Hall effect. Within density functional theory, we evaluate the range of
spin-canting angles in SrRuO$_3$ and demonstrate that it is suppressed as electronic correlations increase. By analyzing the AHC as a function of the canting angle, we find that the collinear
magnetic configurations contribute most to the AHC, while
spin canting plays a secondary role in determining its magnitude in non-collinear ferromagnets and altermagnets. However, canting can become relevant and induce a sign change of the AHC when the collinear
magnetic state exhibits an AHC close to zero. Finally, we investigate the locations of Weyl points in the Brillouin zone and their
evolution as a function of the canting angle.
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All authors Mathews Benny, Xujia Gong, Kamil Jamroszczyk, Amar Fakhredine, Giuseppe Cuono, Rajibul Islam, Jan Skolimowski, Carmine Autieri
Quantum Gases
Experimental study of matter-wave four-wave mixing in $^{39}$K Bose-Einstein condensates with tunable interaction
Yue Zhang, Liangchao Chen, Zekui Wang et al. (+7 more)
We experimentally investigate four-wave mixing (FWM) of matter waves in two
geometric configurations in $^{39}$K Bose-Einstein condensates with the atomic interaction tuned via Feshbach resonances. For one configuration with the single-
spin component, the FWM yield increases with a larger scattering length. For the two-
spin component configuration, we specifically investigate FWM in both the droplet and gas parameter regimes. We find that the FWM yield reaches its maximum near the critical parameter region between the gas and droplet phases. Our research can help to optimize the FWM yield for matter-wave amplification and entangled atom pair generation, making it conducive to applications in
quantum information processing and precision measurement.
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All authors Yue Zhang, Liangchao Chen, Zekui Wang, Yazhou Wang, Pengjun Wang, Lianghui Huang, Zengming Meng, Zhuxiong Ye, Wei Han, Jing Zhang
Disordered Systems and Neural Networks
On generating Special Quasirandom Structures: Optimization for the DFT computational efficiency
Andrzej P. Kądzielawa
We present our novel evolutionary
algorithm for generating Special Quasirandom Structures (SQS) designed to optimize the computational efficiency of Density Functional Theory (DFT) computations. Operating on the premise that
symmetry proxies non-randomness, we rigorously filter out 1.P1 candidate structures prior to evaluating correlation functions. Our extinction-based workflow includes the seeding, filtration, evaluation, extinction, and repopulation phases to produce efficient supercells with maximal local environmental distinctness. We compare our results against those generated by established software packages, on the example of the W\textsubscript{70}Cr\textsubscript{30}
alloy. Although standard tools achieve (marginally) lower correlation errors, our best-performing structures require approximately five times fewer unique displacements for
phonon calculations. This approach sacrifices negligible quantitative disorder accuracy to significantly reduce the computational cost of modeling thermal properties.
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Materials Science
Interlayer-mediated catalyst engineering for ultra-high aspect ratio silicon nanostructures
Bryan Peter Jost Benz, Marco Stampanoni and Lucia Romano
Reliable and precise etching of silicon nanostructures with ultra-high aspect ratios is required in many fields. Metal assisted chemical etching (MacEtch) in vapor is a
plasma-free etching method that attracts considerable
attention owing to the ability to create smooth, high aspect ratio nanostructures. MacEtch understanding and applications are limited by low fidelity and inconsistent pattern transfer from the catalyst layer to the silicon substrate. The locally constrained electrochemical interactions at the catalyst site make MacEtch particularly sensitive to catalyst contamination reducing the reaction rate and pinning the catalyst during etching. Removing contaminants is essential to improve pattern transfer for reliable processes on a larger area and higher aspect ratio. Physically separating the main source of carbon - the resist - from the catalyst with a sacrificial and functional interlayer solves this issue. The interlayer separates the resist and the catalyst and allows for thorough cleaning of the substrate before catalyst deposition. The resulting clean catalyst has improved stability, quality and reproducibility, enabling reliable fabrication of dense (50% patterned area) high aspect ratio (>250:1) nanostructures. Two different interlayer materials (Cr and Al$_{2}$O$_{3}$) and two patterning approaches are presented, showcasing etching of various high aspect ratio nanostructures, such as X-ray Optics.
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Disordered Systems and Neural Networks
Fragile vs robust Multiple Equilibria phases in generalized Lotka-Volterra model with non-reciprocal interactions
Thomas Louis-Sarrola and Valentina Ros
We investigate the Multiple
Equilibria phase of generalized Lotka-Volterra dynamics with random, non-reciprocal interactions. We compute the topological complexity of
equilibria, which quantifies how rapidly the number of
equilibria of the dynamical equations grows with the total number of species. We perform the calculation for arbitrary degree of non-reciprocity in the interactions, distinguishing between configurations that are dynamically stable to invasions by species absent from the
equilibrium, and those that are not. We characterize the properties of typical (i.e., most numerous)
equilibria at a given diversity, including their average abundance, mutual similarity, and internal stability. This analysis reveals the existence of two distinct ME phases, which differ in how internally stable
equilibria behave under invasions by absent species. We discuss the implications of this finding for the system's dynamical behavior.
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Mesoscale and Nanoscale Physics
Enhanced effective masses, spin-orbit polarization, and dispersion relations in 2D hole gases under strongly asymmetric confinement
N. A. Cockton, F. Sfigakis, M. Korkusinski et al. (+13 more)
The dispersion of Rashba-split heavy-hole subbands in GaAs two-dimensional hole gases (2DHGs) is difficult to access experimentally because strong heavy-hole-light-hole mixing produces non-parabolicity and breaks the usual correspondence between carrier density and
Fermi wave vector. Here we use low-field magnetotransport (B < 1 T) to reconstruct the dispersions of the two
spin-orbit-split heavy-hole branches (HH-, HH+) in undoped (100) GaAs/AlGaAs single heterojunction 2DHGs operated in an accumulation-mode field-effect geometry. The dopant-free devices sustain out-of-plane electric fields up to 26 kV/cm while maintaining mobilities up to 84 m$^2$/Vs and exhibiting a
spin-orbit polarization as large as 36%.
Fourier analysis of Shubnikov-de Haas (SdH) oscillations resolves the individual HH-/HH+ subband densities; fitting the temperature dependence of the corresponding
Fourier amplitudes yields both branch-resolved SdH effective masses over the same
magnetic field window. SdH regimes in which reliable subband parameters can be extracted are delineated. Over 2DHG densities (0.76-1.9) $\times$ 10$^{15}$ /m$^2$, the HH- mass is nearly density independent ($\approx 0.34m_e$), implying a near-
parabolic HH- dispersion below the first LH+/HH- anticrossing, whereas HH+ exhibits strong non-parabolicity with an effective mass that increases with density. Combining the extracted dispersions yields a transport-based determination of the
spin-orbit splitting energy $\Delta_\text{HH}$ between HH and HH+ as a function of in-plane wave vector. Parameter-free Luttinger-model calculations reproduce the qualitative trends but underestimate both masses by a common factor $\approx$ 2, suggesting a many-body renormalization of the heavy-hole mass in this strongly asymmetric regime.
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All authors N. A. Cockton, F. Sfigakis, M. Korkusinski, S. R. Harrigan, G. Nichols, Z. D. Merino, T. Zou, A. C. Coschizza, T. Joshi, A. Shetty, M. C. Tam, Z. R. Wasilewski, S. A. Studenikin, D. G. Austing, J. Baugh, J. B. Kycia
Superconductivity
Spatial homogeneity of superconducting order parameter in NbN films grown by atomic layer deposition
J. Lorenz, S. Linzen, M. Ziegler et al. (+5 more)
Due to their high kinetic inductance, highly disordered superconducting thin films are a potential hardware for the realization of compact, low-noise elements in cryoelectronic applications. However, high disorder typically results in structural defects that cause spatial inhomogeneity of the superconducting order parameter, thereby impairing the film's properties. Here, we employ scanning tunneling microscopy to demonstrate that NbN thin films fabricated by
plasma-enhanced atomic layer deposition (PE-ALD) exhibit unusual spatial homogeneity, even at thicknesses approaching the
superconductor-
insulator transition. Tunneling spectra acquired across the sample surface show only small variations of the order parameter with a standard deviation of 2-3%, on length scales that significantly exceed the film's grain size. At the same time, the films achieve a relatively high sheet resistance (up to 1400 Ohm) and, consequently, a high sheet kinetic inductance (up to approximately 200 pH), making them well-suited for applications.
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All authors J. Lorenz, S. Linzen, M. Ziegler, G. Oelsner, R. Stolz, F. S. Tautz, F. Lüpke, E. Il'ichev
Strongly Correlated Electrons · Cross-listed from quant-ph
Emulation of large-scale qubit registers with a phase-space approach
Christian de Correc, Denis Lacroix and Corentin Bertrand
A phase-space approach is used and benchmarked for the simulation of the continuous-time
evolution of large registers of
qubits. It is based on a statistical ensemble of independent mean-field trajectories, where mean field is introduced at the level of the
qubits, substituting
quantum fluctuations/correlations with classical ones. The approach only involves at worse a quadratic cost in the system size, allowing to simulate up to several thousands of
qubits on a classical computer. It provides qualitatively accurate description of one-
qubit observables evolutions, making it a useful reference in comparison to techniques limited to small
qubit numbers. The predictive power is, however, less robust for multi-
qubits observables. We
benchmark the method on the $k$-local transverse-field Ising model, considering a large variety of systems ranging from local to all-to-all interactions, and from weak to strong coupling regimes, with up to 2000
qubits. To showcase the versatility of the approach, simulations on 2D and 3D Ising models are also made.
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Statistical Mechanics
Scaling and Universality at Noise-Affected Non-Equilibrium Spin Correlation Functions
R. Jafari and Alireza Akbari
We investigate scaling and universality in nonequilibrium
spin correlation functions in the presence of uncorrelated noise. In the absence of noise,
spin correlation functions exhibit a crossover from monotonic decay at fast sweep velocities to oscillatory behavior at slow sweeps. We show that, under a stochastically driven field, the critical sweep velocity at which the
spin correlation functions undergo an abrupt change decreases with increasing noise strength and scales linearly with the square of the noise intensity. Remarkably, when the noise intensity and sweep velocity are comparable, the excitation probability becomes locked to pk = 1/2 over a finite momentum window, signaling the emergence of noise-induced maximally mixed modes. This gives rise to a highly oscillatory region in the dynamical phase diagram, whose threshold sweep velocity increases with noise and likewise exhibits quadratic scaling with the noise strength. Finally, we identify a universal scaling function under which all boundary sweep-velocity curves collapse onto a single universal curve.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.app-ph
Establishing the Magnetoelastic Origin of Spin-Wave Routing through Focused Ion Beam Patterning
Felix Naunheimer, Johannes Greil, Valentin Ahrens et al. (+4 more)
Spin waves are promising information carriers for analog and wave-based computing, where functionality relies on compact and precisely engineered scattering landscapes. Focused ion beam (FIB) irradiation enables such control by locally tailoring the
spin-wave dispersion in yttrium iron garnet (YIG). However, a non-monotonic dependence of the
spin-wave wavelength on increasing ion dose hinders predictive landscape design. Here, we present an experimentally validated framework that explains this non-monotonic
spin-wave steering by linking phenomenological strain-induced anisotropy to its magnetoelastic origin. Irradiation-induced
lattice dislocations drive elastic and plastic deformation, which evolve into partial amorphization, each stage contributing distinctly to the dispersion behavior. We combine post-irradiation wet-chemical etching and atomic force microscopy (AFM) to quantify thickness changes, and track the dispersion in etched regions using time-resolved magneto-optical Kerr effect (trMOKE) microscopy. Fitting the data to the Kalinikos–Slavin formalism with an added effective magnetoelastic field isolates contributions from elastic and plastic deformation. Validation is achieved by mapping the deformation
evolution onto a three-phase scenario based on SRIM simulations, reproducing the extracted field trends, and by consistent strain tensor and micromagnetic analyses. These results establish a physical basis for FIB-engineered graded-index (GRIN)
spin-wave landscapes and magnetoelastically programmable magnonic devices.
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All authors Felix Naunheimer, Johannes Greil, Valentin Ahrens, Levente Maucha, Ádám Papp, György Csaba, Markus Becherer
Materials Science
Distorted polyhedral architecture enabled high thermoelectric performance of columnar double halide perovskites Cs2AgPdCl5 and Cs2AgPtCl5
Heena, Vineet Kumar Pandey, Ambesh Dixit et al. (+3 more)
We investigate the thermoelectric properties of two newly synthesized columnar double halide perovskites Cs$_2$AgPdCl$_5$ and Cs$_2$AgPtCl$_5$. These materials accommodate a distorted local polyhedral architecture with tetrahedral
symmetry compared to traditional double halide perovskites. By employing density functional theory along with the semiclassical transport model, we have analyzed the electronic and transport properties of these materials. Our results show that at 800 K, the largest figure of merit ($zT$) is 1.30 (0.86) for p-type (n-type) Cs$_2$AgPdCl$_5$ and 0.87 for n-type Cs$_2$AgPtCl$_5$ at doping concentrations of $1.94 \times 10^{20}$ ($3.76 \times 10^{19}$) cm$^{-3}$ and $3.52 \times 10^{19}$ cm$^{-3}$, respectively. Remarkably, a very low doping concentration is required to achieve a high $zT$, setting these materials apart from others in this field. Our calculations demonstrate that Cs$_2$AgPdCl$_5$ benefits from the presence of conduction and valence band valleys near the band edges; however, the flat bands present in the valence band of Cs$_2$AgPtCl$_5$ do not improve its thermoelectric performance. Among these systems, hole doping in Cs$_2$AgPdCl$_5$ has shown remarkable thermoelectric performance. Interestingly, the local octahedral distortions present in these perovskites contribute to a marked reduction in the
lattice thermal conductivity to 0.27 W/mK in Cs$_2$AgPtCl$_5$ and 0.20 W/mK in Cs$_2$AgPdCl$_5$ by causing enhanced
phonon scattering, further improving the thermoelectric figure of merit. This drop in thermal conductivity, combined with the favorable electronic properties, underscores the potential use of these materials for applications in highly efficient thermoelectric devices.
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All authors Heena, Vineet Kumar Pandey, Ambesh Dixit, Anver Aziz, Sung Gu Kang, K.C. Bhamu
Statistical Mechanics
A statistical theory of structure in many-particle systems with local interactions
John Çamk{\i}ran, Fabian Parsch and Glenn D. Hibbard
A theory of structure is formulated for systems of many structureless classical particles with stable local interactions in Euclidean space. Such systems are shown to have their structure in thermodynamic
equilibrium determined exactly by a random field of fine local descriptions and approximately by coarsenings thereof. The degree of order in the local cluster consisting of a particle and its neighbors is identified as a universal source of coarse local descriptions and characterized by expressing the behavior of configurational
entropy in local microscopic terms. A local measure of the angular redundancy in neighboring particle positions is found to satisfy this characterization and thereby established as a valid local order quantifier. A precise relationship between order and
symmetry is obtained by bounding this quantifier sharply from below by a simple function of the local point group and the largest stabilizer under its action on the set of bond pairs. The marginal distribution of the quantifier is given in closed form for highly coordinated particles with broadly distributed bond angles. Applications are made to the ideal gas, perfect
crystal, and simple
liquid.
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Statistical Mechanics · Cross-listed from physics.hist-ph
Between equilibrium and fluctuation: Einstein's heuristic argument and Boltzmann's principle
Enric Pérez and Antonio Gil
We critically revisit Einstein's 1905 heuristic argument for lightquanta, considering its internal coherence and the scope of its applicability. We argue that Einstein's
reasoning, often celebrated for its originality, is ambiguous because it can be understood as a fluctuation or as a comparison between
equilibrium states. A historical and conceptual analysis of Einstein's use of Boltzmann's principle in those years reveals his evolving stance on its meaning and the role of probability, as well as his persistent doubts about the nature of radiation. We use our analysis to examine the limitations of extending the notion of Einstein's lightquanta across the electromagnetic spectrum: the relevant parameter is not the frequency, but the occupancy number.
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Materials Science
Layer-dependent antiferromagnetic Chern and axion insulating states in UOTe
Sougata Mardanya, Barun Ghosh, Mengke Liu et al. (+8 more)
Magnetic topological
insulators have received significant interest due to their dissipationless edge states, which promise advances in energy-efficient electronic transport. However, the
magnetic topological
insulator state has typically been found in ferromagnets (FMs) that suffer from low
magnetic ordering temperatures and stray fields. Identifying an
antiferromagnetic topological
insulator that exhibits the
quantum anomalous
Hall effect (QAHE) with a relatively high Néel temperature has been a longstanding challenge. Here, we focus on the recently discovered van der Waals (vdW) antiferromagnet (AFM) UOTe, which not only features a high Néel temperature (\(\sim\)150K) but also exhibits intriguing Kondo interaction and topological characteristics. Our systematic analysis of the layer-dependent topological phases based on ab initio computations predicts the two-layer UOTe film to be an ideal 2D AFM Chern
insulator in which the
Hall conductivity is quantized with a fully compensated
spin magnetization. By applying an in-plane strain or electric field, we show how the itinerancy of U-5f electrons can be manipulated to trigger a transition between the nontrivial ($C = 1$) and trivial ($C = 0$) phases. Interestingly, the 3-layer UOTe film is found to have zero charge conductance but it hosts a quantized
spin Hall conductivity (SHC) with finite magneto-electric coupling, suggesting the presence of an
axion insulator-like state. The unique
magnetic structure of UOTe supports a layer-tunable
topology in which films with an odd number of layers are
axion-like
insulators, while films with an even number of layers are Chern
insulators, and the bulk material is a Dirac semimetal. Our study offers a new intrinsic AFM materials platform for realizing correlated topological phases for next-generation spintronics applications and fundamental science studies.
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All authors Sougata Mardanya, Barun Ghosh, Mengke Liu, Christopher Broyles, Junyeong Ahn, Kai Sun, Jennifer E. Hoffman, Sheng Ran, Arun Bansil, Su-Yang Xu, Sugata Chowdhury
Materials Science · Cross-listed from quant-ph
Magneto-optical properties of the neutral silicon-vacancy center in diamond under extreme isotropic strain fields
Meysam Mohseni, Gergő Thiering and Adam Gali
The neutral silicon–vacancy (SiV$^{0}$) center in diamond combines inversion
symmetry with optical emission, making it a robust
quantum emitter resilient to stray electric fields. Using first-principles density-functional theory, we quantify its response to isotropic strain spanning strong compression and tensile regimes (effective hydrostatic pressures of approximately $-80$ to $180$~GPa). The coexistence of doubly degenerate $e_g$ and $e_u$ levels produces a structural instability captured by a quadratic product Jahn–Teller model. Under isotropic compression, the zero-
phonon line blue-shifts nearly linearly while the $E_g$
phonon stiffens, suppressing vibronic instabilities and reducing Jahn–Teller quenching. Consequently, the Ham-reduced excited-state
spin–orbit splitting increases substantially and the dark–bright vibronic gap widens. In contrast, isotropic tensile strain enhances vibronic effects and induces
symmetry breaking beyond a critical strain, with tunneling-mediated dynamical averaging at the onset. Throughout the
symmetry-preserving regime, parity remains well defined, so isotropic strain alone does not activate the dark transition. Charge-transition levels indicate photostability of the emission deep into the compressive regime, and near the highest photostable deformation ($\sim 100$~GPa), the radiative lifetime increases due to a reduced transition dipole moment despite the increasing optical energy. These trends yield compact calibration relations linking optical and
spin observables to isotropic strain and establish SiV$^{0}$ as a
symmetry-protected, strain-tunable
quantum emitter operating into the multi-megabar-equivalent regime.
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Disordered Systems and Neural Networks · Cross-listed from stat.ML
A solvable high-dimensional model where nonlinear autoencoders learn structure invisible to PCA while test loss misaligns with generalization
Vicente Conde Mendes, Lorenzo Bardone, Cédric Koller et al. (+4 more)
Many real-world
datasets contain hidden structure that cannot be detected by simple linear correlations between input features. For example, latent factors may influence the data in a coordinated way, even though their effect is invisible to covariance-based methods such as PCA. In practice, nonlinear neural networks often succeed in extracting such hidden structure in unsupervised and self-supervised learning. However, constructing a minimal high-dimensional model where this advantage can be rigorously analyzed has remained an open theoretical challenge. We introduce a tractable high-dimensional spiked model with two latent factors: one visible to covariance, and one statistically dependent yet uncorrelated, appearing only in higher-order moments. PCA and linear autoencoders fail to recover the latter, while a minimal nonlinear autoencoder provably extracts both. We analyze both the population risk, and empirical risk minimization. Our model also provides a tractable example where self-supervised test loss is poorly aligned with representation quality: nonlinear autoencoders recover latent structure that linear methods miss, even though their reconstruction loss is higher.
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All authors Vicente Conde Mendes, Lorenzo Bardone, Cédric Koller, Jorge Medina Moreira, Vittorio Erba, Emanuele Troiani, Lenka Zdeborová
Statistical Mechanics
Analytic Nonlinear Theory of Shear Banding in Amorphous Solids
Avanish Kumar and Itamar Procaccia
The aim of this paper is to offer an analytic theory of the shear banding instability in amorphous solids that are subjected to athermal quasi-static shear. To this aim we derive nonlinear equations for the displacement field, including the consequences of plastic deformation on the mechanical response of amorphous solids. The plastic events collectively induce distributed dipoles that are responsible for screening effects and the creation of typical length-scales that are absent in classical elasticity theory. The nonlinear theory exposes an instability that results in the creation of shear bands. By solving the weakly nonlinear amplitude equation we present analytic expressions for the displacement fields that is associated with shear bands, explaining the role of the elastic
moduli that determine the width of a shear band from ductile to brittle characteristics. We derive an energy functional whose Hessian possesses an
eigenvalue that goes to zero at the shear-banding instability, providing a prediction for the critical value of the accumulated stress that results in an instability.
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Materials Science
Nonlinear dynamics in magnonic Fabry-Pérot resonators: Low-power neuron-like activation and transmission suppression
Anton Lutsenko, Kevin G. Fripp, Lukáš Flajšman et al. (+3 more)
We report on nonlinear
spin-wave dynamics in magnonic Fabry-Pérot resonators composed of yttrium iron garnet (YIG) films coupled to CoFeB nanostripes. Using super-Nyquist sampling magneto-optical Kerr effect microscopy and micromagnetic simulations, we observe a systematic downshift of the
spin-wave transmission gaps as the excitation power increases. This nonlinear behavior occurs at low power levels, reduced by a strong spatial concentration of
spin waves within the resonator. The resulting power-dependent transmission enables
neuron-like activation behavior and frequency-selective nonlinear
spin-wave absorption. Our results highlight magnonic Fabry-Pérot resonators as compact low-power nonlinear elements for neuromorphic magnonic computing architectures.
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All authors Anton Lutsenko, Kevin G. Fripp, Lukáš Flajšman, Andrey V. Shytov, Volodymyr V. Kruglyak, Sebastiaan van Dijken
Materials Science
Antiferroaxial altermagnetism
Yichen Liu and Cheng-Cheng Liu
The antiferroaxial state is emerging as an important ferroic order in condensed matter systems. Here, we establish antiferroaxial altermagnetism as a broadly prevalent, generic, and microscopically grounded multiferroic mechanism, in which antiferroaxial counter-rotating distortions both induce altermagnetism and enable its deterministic and reversible switching. Within a unified Landau-theory and
symmetry framework, we identify a
symmetry-allowed trilinear invariant coupling the antiferroaxial order, the Néel vector, and the altermagnetic order, and derive general
symmetry criteria for its occurrence. This coupling locks the induced altermagnetism to the antiferroaxial order, so that reversing the latter reverses the
spin splitting and associated time-reversal-odd responses, such as anomalous
Hall conductivity. We provide a practical
spin group dictionary mapping Néel-vector representations to the resulting $d$-, $g$-, and $i$-wave antiferroaxial altermagnetism, validate the mechanism with ligand-rotation tight-binding models and first-principles calculations, and identify many candidate materials by screening the MAGNDATA and C2DB databases. Our results elevate antiferroaxiality to a universal ferroic control knob for structurally programmable altermagnetic spintronics.
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Statistical Mechanics · Cross-listed from cs.LG
Coarse-Grained Boltzmann Generators
Weilong Chen, Bojun Zhao, Jan Eckwert et al. (+1 more)
Sampling
equilibrium molecular configurations from the Boltzmann distribution is a longstanding challenge. Boltzmann Generators (BGs) address this by combining exact-likelihood generative models with importance sampling, but practical scalability is limited. Meanwhile, coarse-grained surrogates enable the modeling of larger systems by reducing effective dimensionality, yet often lack a reweighting procedure required to ensure asymptotically correct statistics. In this work, we propose Coarse-Grained Boltzmann Generators (CG-BGs), a framework for reduced-order generative modeling with importance sampling in coarse-grained coordinate space. CG-BGs generate samples using a flow-based model and reweight them using a learned potential of mean force (PMF). We show that the PMF can be learned from rapidly converged trajectories via enhanced sampling force matching. Experiments demonstrate that CG-BGs capture solvent-mediated interactions in highly reduced representations while substantially reducing computational cost relative to atomistic BGs, providing a practical route toward
equilibrium sampling of larger molecular systems.
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All authors Weilong Chen, Bojun Zhao, Jan Eckwert, Julija Zavadlav
Superconductivity
Universality of linear in temperature and linear in field Planckian scattering rate in high temperature cuprate superconductors
K. Remund, K. V. Nguyen, P.-H. Chou et al. (+4 more)
One of the long standing puzzles in strongly correlated materials is the microscopic origin of the
quantum critical Planckian strange metal phase with universal linear in temperature scattering rate from which unconventional superconductivity directly emerges by lowering temperatures. Recently, the linear in temperature and linear in field resistivity have been simultaneously observed in high temperature cuprate
superconductors, manifested by the universal field to temperature scaling in magnetoresistivity. To date, there has been a lack of coherent and unified understanding of these coexisting linear behaviors and their possible link to
quantum criticality. In this work, we establish the universality in linear in temperature and linear in field Planckian behaviors in underdoped LSCO near optimal doping. Experimentally, we observe the linear in field Planckian scattering rate and its relation to its linear in temperature counterpart. Theoretically, we propose a
spin based common microscopic mechanism based on Kondo-like charge fluctuations near local
quantum criticality of heavy
fermion formulated tJ model subject to a Zeeman term. Similar to frequency to temperature scaling near
quantum criticality, we find the
magnetic field here effectively introduces a Zeeman energy, reminiscent of an external energy in the
quantum critical regime, leading to field to temperature scaling. Our analytically predicted universal field to temperature scaling in isotropic scattering rate and the relation between the linear in temperature and linear in field Planckian coefficients, unifies these two phenomena over an extended doping range, pointing toward a unified
quantum-critical origin of Planckian transport in cuprates.
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All authors K. Remund, K. V. Nguyen, P.-H. Chou, P. Giraldo-Gallo, J. A. Galvis, G. S. Boebinger, C.-H. Chung
Statistical Mechanics
Interplay of ion availability and mobility in the loss of cation selectivity for CaCl\textsubscript{2} in negatively charged nanopores: molecular dynamics using scaled-charge models
Salman Shabbir, Dezső Boda and Zoltán Ható
Ion transport through charged nanopores is commonly interpreted in terms of electrical double layer structure, leading to the expectation of cation-selective conduction in negatively charged pores. This picture can break down for multivalent electrolytes, where strong ion-urface correlations and charge inversion modify transport behavior. Here, we study NaCl and CaCl$_2$ conduction through negatively charged silica nanopores using atomistic molecular dynamics simulations with scaled-charge ion models. By separating concentration and velocity contributions to the radial particle current density, we connect static adsorption to dynamic perm-selectivity. While NaCl exhibits conventional cation selectivity, CaCl$_2$ shows nearly bulk-like or even anion-favored transport due to Ca$^{2+}$ immobilization near the surface and dominant Cl$^-$ conduction in the pore interior following charge inversion. Although this qualitative mechanism is robust, its detailed manifestation depends sensitively on the balance of ion-surface and ion-water interactions encoded in the force field.
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Statistical Mechanics
Thermodynamic Optimization of Sensory Adaptation via Game-Theoretic Path Integrals
Gunn Kim
Biological sensory systems, from E.~coli chemotaxis to sensory
neurons in C.~elegans, achieve reliable adaptation over wide dynamic ranges despite operating in strongly noisy and overdamped regimes. Here, we present a field-theoretic framework in which sensory adaptation emerges from a variational free-energy principle, formulated as a
stochastic differential game between an organism and its environment. Using an Onsager–Machlup path-integral formalism, we show that the resulting adaptive dynamics are mathematically equivalent to a class of model reference adaptive control schemes and can be interpreted as a dynamic renormalization of the system's Green's function. Within this framework, the phasic overshoot commonly observed in sensory responses arises naturally from an effective inertia ($m^* \approx \tau \gamma$) generated by
memory-dissipation coupling, rather than from biochemical fine-tuning. Quantitative fits to experimental data across species yield $R^2 > 0.88$, and indicate that adaptive sensory processing operates within a narrow thermodynamically optimal regime bounded by signal-to-noise and stability constraints.
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