Mesoscale and Nanoscale Physics
Dynamics of antiskyrmion shrinking
Frederik Austrup, Wolfgang Häusler, Michael Lau et al. (+1 more)
Antiskyrmions are unstable in
ferromagnetic systems with isotropic bulk or interfacial Dzyaloshinskii-Moriya interaction (DMI). We develop a continuum model for the shrinking dynamics of antiskyrmions in bulk DMI systems, using the Landau-Lifshitz-Gilbert equation for the time derivative of the magnetization field. Owing to the structure of their azimuthal angle, or helicity,
elliptic antiskyrmions are energetically favored over circular ones. To capture this feature, we parametrize the magnetization field with a triangular radial profile and an
elliptic in-plane shape. This ansatz yields four coupled dynamical equations governing time
evolution of the semi-axes, helicities, and rotation angles. In the absence of the DMI, circular antiskyrmions shrink isotropically, exhibiting a crossover from exponential decay to square-root collapse. Initially
elliptic antiskyrmions are driven towards circularity. For finite DMI, the semi-axes dynamics couples to the helicity and rotation, where the theory predicts a rotation angle following by half of the slope of the helicity
evolution which is linear in time. Only at small semi-axes a cross-over to a logarithmic divergence occurs. The shrinking dynamics of the antiskyrmion size is found to be accompanied by quadrupole-like oscillations. Numerical simulations on the
lattice support the predictions from the continuum model.
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All authors Frederik Austrup, Wolfgang Häusler, Michael Lau, Michael Thorwart
Quantum Gases
Soliton-to-droplet crossover in a dipolar Bose gas in one and two dimensions
Malte Schubert, Thomas Bland, Manfred J. Mark et al. (+2 more)
We analyze a system of dipolar atoms confined in geometries of quasi-low-dimensionality. Due to the long-range and anisotropic nature of dipolar interactions, the system supports both stable
solitons and
quantum droplets. In quasi-one-dimensional geometries, the transition between these states is known to manifest either as a first-order phase transition, associated with bistability, or as a smooth crossover. We investigate this transition by calculating the structure factor and showing that the response of the breathing mode provides an experimentally accessible probe. In addition, we identify regions of both bistability and smooth crossover in quasi-two-dimensional geometries. Finally, we connect our findings to previous experimental results and delineate the conditions under which two-dimensional dipolar bright
solitons can be realized.
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All authors Malte Schubert, Thomas Bland, Manfred J. Mark, Francesca Ferlaino, Stephanie Reimann
Materials Science
Resolving Structural Avalanches in Amorphous Carbon with Arclength Continuation
Fraser Birks, Ibrahim Ghanem, Lars Pastewka et al. (+2 more)
Plastic deformation in amorphous solids is carried by localized shear transformations that self-organize into avalanches. In amorphous carbon modeled with a machine-learned interatomic potential, we find that the energetics and organization of these avalanches can be resolved by systematically following the underlying energy landscape. With a pseudo-arclength numerical continuation framework, we decompose avalanches into constituent shear transformations and determine their strain-dependent energetics. Our analysis shows that, prior to onset, avalanches have a latent structure that consists of well-separated local minima. We further demonstrate that arclength continuation yields an event driven framework for following avalanche dynamics, eliminating time-step effects on statistical avalanche properties such as distributions of stress drops.
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All authors Fraser Birks, Ibrahim Ghanem, Lars Pastewka, James Kermode, Maciej Buze
Strongly Correlated Electrons
Spiral Phase and Phase Diagram of the $S$=1/2 XXZ Model on the Shastry-Sutherland Lattice
Zhengpeng Yuan, Muwei Wu, Dao-Xin Yao et al. (+1 more)
We investigate the ground-state phase diagram of the $S$=1/2 XXZ model on the two-dimensional Shastry-Sutherland
lattice using exact diagonalization (ED), density-
matrix renormalization group (DMRG), and cluster mean-field theory (CMFT) with DMRG as a solver. In the isotropic case ($\Delta=1$), CMFT results reveal an intermediate empty plaquette (EP) phase that has a lower energy than the full plaquette (FP) phase. However, due to mean-field artifacts, CMFT alone is not suitable for accurately determining phase boundaries. Therefore, we combined three methods to map out the reliable phase diagram. Our calculations show that the EP phase narrows as $\Delta$ deviates from unity and eventually vanishes. More importantly, we identify a spiral phase at small $\Delta$, which has not been reported in previous studies. This phase is clearly captured by DMRG simulations on long cylindrical geometries. The competition between the EP, spiral, and $xy$-AFM phases near their boundaries provides a plausible explanation for the emergent
spin-
liquid-like behavior in RE$_2$Be$_2$GeO$_2$, while shedding new light on the role of XXZ anisotropy in the Shastry-Sutherland XXZ model.
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All authors Zhengpeng Yuan, Muwei Wu, Dao-Xin Yao, Han-Qing Wu
Strongly Correlated Electrons
$q$-state Potts ice
Mark Potts, S.A. Parameswaran and Roderich Moessner
Classical and
quantum spin ice arguably provide the simplest route towards
spin liquids and their emergent gauge fields. $q-$state Potts ice models have been constructed that generalize
spin ice, hosting multiple emergent $\text{U}(1)$ gauge fields and excitations charged under non-trivial combinations of these fields. We present a general treatment of classical $q-$state Potts ices relating their properties to the $\mathfrak{su}(q)$ Lie
algebras, and demonstrate how the properties of charged excitations in the classical model can be related to this
symmetry group. We also introduce
quantum generalizations of the Potts ice models, and demonstrate how charge
flavor changing interactions unique to $q>2$ models dominate their low energy physics. We further show how
symmetries inherited from the $\mathfrak{su}(q)$ can lead to flux
vacuum frustration, greatly modifying the dynamical properties of charged excitations.
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Materials Science · Cross-listed from stat.CO
A Framework for the Bayesian Calibration of Complex and Data-Scarce Models in Applied Sciences
Christina Schenk and Ignacio Romero
In this work, we review the theory involved in the
Bayesian calibration of complex computer models, with particular emphasis on their use for applications involving computationally expensive simulations and scarce experimental data. In the article, we present a unified framework that incorporates various
Bayesian calibration methods, including well-established approaches. Furthermore, we describe their implementation and use with a new, open-source Python library, ACBICI (A Configurable
BayesIan Calibration and Inference Package). All
algorithms are implemented with an object-oriented structure designed to be both easy to use and readily extensible. In particular, single-output and multiple-output calibration are addressed in a consistent manner. The article completes the theory and its implementation with practical recommendations for calibrating the problems of interest. These guidelines – currently unavailable in a unified form elsewhere – together with the open-source Python library, are intended to support the reliable calibration of computational codes and models commonly used in engineering and related fields. Overall, this work aims to serve both as a comprehensive review of the statistical foundations and (computational) tools required to perform such calculations, and as a practical guide to
Bayesian calibration with modern software tools.
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Statistical Mechanics
Leveraging Interactions for Efficient Swarm-Based Brownian Computing
Alessandro Pignedoli, Atreya Majumdar and Karin Everschor-Sitte
Drawing inspiration from swarm intelligence, we show that short-range attractive interactions between thermally driven Brownian quasiparticles enable energy-efficient optimization. As quasiparticles can be generated directly within a material, the swarm size can be adjusted with minimal energy overhead. Using an optimization task defined by a spatially varying temperature landscape, we quantitatively show that interacting swarms reliably identify global optima and significantly outperform non-interacting searchers within a well-defined regime of interaction strength and swarm size. This improvement arises from emergent cooperative behavior, where local interactions guide the swarm toward high-quality solutions without central coordination. To link our physical model to experimental realizations, we coarse-grain the quasiparticle dynamics onto a sensor
lattice and generate trajectories emulating particle-tracking measurements. We further show that the interacting swarm adapts robustly to landscapes that evolve over time. These findings establish interacting Brownian quasiparticles as a physical platform for scalable and energy-efficient unconventional computing.
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Mesoscale and Nanoscale Physics
Gate-tuneable single-photon emitters in WSe2 monolayer created via AFM nanoindentation on rigid SiO2/Si substrates
Ajit Kumar Dash, Sanket Jugade, Manavendra Pratap Singh et al. (+12 more)
Single-
photon emitters (SPEs) hosted by two-dimensional (2D) semiconducting materials are envisioned for next-generation
quantum applications. However, SPE creation in 2D
semiconductors on rigid substrates like SiO2/Si via nanoindentation is a technological gap, critical for interfacing SPEs with photonic
circuits and cavities. Here, we report a protocol for deterministically creating SPEs in monolayer WSe2 on SiO2/Si substrates using a sharp diamond AFM (atomic force microscope) tip. A displacement-controlled indentation process is developed, allowing indent depths > 150 nm necessary for creating SPEs. Sharp defect peaks (~200 {\mu}eV) are observed in cryogenic (4K) photoluminescence (PL) spectrum at nanoindented sites and are stable upto ~ 120K. 76% of sites exhibit sharp defect-bound peaks confirmed by power-dependent, temperature-dependent, and time-resolved PL (TRPL). AFM and PL mapping link these peaks to indent periphery. The peaks show sub-linewidth spectral jitter, no blinking, and single-
photon nature in second-order autocorrelation measurements. SPEs can be switched on/off, and background emissions suppressed using electrical gating. Gate-voltage dependent TRPL indicate that SPE dynamics can be tuned, depending on nature of SPE, pointing the way to higher-purity SPEs. Our work is directly applicable to other 2D materials and photonic
circuit/cavity compatible rigid substrates and is a significant step for scalable SPE technologies.
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All authors Ajit Kumar Dash, Sanket Jugade, Manavendra Pratap Singh, Hardeep, Tilly Guyot, Cora Crunteanu-Stanescu, Indrajeet Dhananjay Prasad, Yunus Waheed, Sumitra Shit, Sébastien Roux, Santosh Kumar, Cedric Robert, Xavier Marie, Akshay Naik, Akshay Singh
Materials Science
Fully Compensated Lines in Ferrimagnets
Qais Ali, Anna Grünebohm, Halil Ibrahim Sözen et al. (+3 more)
We generalize the classic Néel diagram and identify another type of ferrimagnetic phase that remains fully magnetically compensated below the Curie temperature, forming a continuous line of compensated points. It exhibits zero net magnetization while retaining non-relativistic, eV-scale reciprocal
spin splitting. We further find a persistently enhanced intrinsic switching field over a broad temperature range near the fully compensated phase. Proximity to the compensated line is achieved by minimizing the net local moment while balancing exchange interactions with respect to the number of equivalent atoms in each sublattice. The resulting extended Néel diagram provides practical design rules for engineering fully compensated ferrimagnetic phases via targeted chemical substitution that combines atoms with robust and weak local moments, as demonstrated through density functional theory and Monte Carlo simulations for GdCo$_5$-type ferrimagnets.
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All authors Qais Ali, Anna Grünebohm, Halil Ibrahim Sözen, Tilmann Hickel, Jörg Neugebauer, Eduardo Mendive-Tapia
Statistical Mechanics
Synchronization and phase transition of two-dimensional self-rotating clock models
Xin Wu and Mingcheng Yang
We explore possible synchronization in two-dimensional (2D) locally coupled discrete-state oscillators under thermal fluctuations, using the self-rotating $q$-state clock model as a prototype. Large-scale Monte Carlo simulations reveal that for $q \ge q_c$ (with $q_c = 5$), the system undergoes two-step Berezinskii-Kosterlitz-Thouless (BKT)-like transitions: first from a disordered phase to a critical synchronized phase, and then to a spatiotemporal pattern phase. Notably, the synchronized phase features algebraically decaying spatial correlations and divergent coherence time, realizing an effective continuous time
crystal across macroscopic yet finite scales; while it vanishes when $q < q_c$. A dynamic renormalization group analysis shows this behavior arises from an emergent U(1)
symmetry for $q \ge q^{RG}_c=5$, and indicates a crossover scale to Kardar-Parisi-Zhang (KPZ) universality diverges double-exponentially with $q$, ensuring the pre-asymptotic stability of the synchronized phase. Mean-field theory predicts a lower critical value $q_c^{MF} = 4$.
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Materials Science
Magnetization reversal and anisotropies in buffered transition-metal alloys thin films
Agostina Lo Giudice, Augusto Román and Laura Beatriz Steren
Interest in planar
Hall effect (PHE) sensors has re-emerged in recent years due to their promising potential for a wide range of applications, particularly in biotechnology. Sensor sensitivity can be enhanced by lowering the effective anisotropy field; however, this favors
magnetic domain formation during magnetization reversal, leading to hysteretic responses. Therefore, precise control of
magnetic anisotropy and magnetization reversal is essential to balance sensitivity and stability in PHE sensors. In this work, we investigate the
magnetic anisotropy and magnetization reversal mechanisms of Ni-Fe- and Co-Fe-based multilayers grown on various metallic buffer layers and deposited with and without an external
magnetic field, in order to evaluate the effects of the buffer layers and field-assisted deposition on the resulting
magnetic anisotropy. NiFe films exhibit a dominant uniaxial anisotropy mainly determined by the applied field during growth, with an anisotropy constant of approximately $3,\mathrm{kerg,cm^{-3}}$, largely independent of the buffer layer. In contrast, the
magnetic anisotropy of CoFe films is dominated by the buffer layer, resulting in a biaxial
magnetic response. In particular, Ag-buffered films deposited under an external
magnetic field exhibit a biaxial anisotropy with values up to $14.88,\mathrm{kerg,cm^{-3}}$. The magnetization reversal mechanism of each system was deduced from the analysis of the angular dependence of the coercive field.
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Materials Science
Ferroelectric switching at edge dislocations in BaTiO$_3$ modelled at the atomic scale
Himal Wijekoon, Pierre Hirel and Anna Grünebohm
Ferroelectric switching governs the functional properties of ferroelectric perovskites. It is widely accepted that this switching depends on domain nucleation and pinning and that these processes can be controlled by the defect structure. However, an atomistic picture of the influence of one important class of defects - dislocations on ferroelectric switching is missing. This is an important gap in knowledge as dislocations cannot be avoided at interfaces and can also be engineered by plastic deformation at high temperatures. Using atomistic simulations, we show how the cores of $\langle100\rangle$ edge dislocations in BaTiO$_3$ can either act as nucleation centers for ferroelectric switching or pin walls depending on the direction of the applied field. The coupling between electric field and polarization is strongest when the field is applied parallel to the Burgers vector of the dislocation.
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Materials Science
Long-distance spin transport in frustrated hyperkagome magnet Gd3Ga5O12
Di Chen, Bingcheng Luo, Lei Xu et al. (+17 more)
Transport of
spin angular momentum over large distance has been a long sought-after goal in the field of spintronics. While the majority of the research effort has been devoted to the
spin transport properties of magnetically ordered materials,
spin transport in magnetically frustrated materials has received little
attention. Here, we report an anomalous state in frustrated hyperkagome
magnetic insulator Gd3Ga5O12, where
spin angular momenta can be transported over a long distance of 480 {\mu}m, far exceeding the transport distance of any diffusive
spin current in magnetically ordered materials, to the best of our knowledge. Monte Carlo simulations reveal significant
spin fluctuations,
spin-
spin correlations and an absence of conventional
magnons in such anomalous state; while the response of the anomalous state to perturbation is found to be akin to an overdamped forced oscillator. We find close relation of such state to the correlated “director” state in the material. Our result provides an effective electrical technique to characterize
spin-
spin correlations and frustrations; it also unveils the potential of frustrated magnets as powerful channel materials for
spin transport.
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All authors Di Chen, Bingcheng Luo, Lei Xu, Zian Xia, Linhao Jia, Shaomian Qi, Congkuan Tian, Kangyao Chen, Hang Cui, Guangyi Chen, Shili Yan, Miaoling Huang, Jian Cui, Ya Feng, Zhentao Wang, Jiang Xiao, Jianhua Zhang, Ryuichi Shindou, X.C. Xie, Jian-Hao Chen
Materials Science
Francesco Foggetti, Francesco Cosco, Peter M. Oppeneer et al. (+4 more)
Terahertz radiation pulses can be generated efficiently through femtosecond
laser excitation of a
ferromagnetic/nonmagnetic
heterostructure, wherein an ultrafast
laser-induced
spin current results in an electromagnetic THz pulse due to
spin-charge conversion. It is, however, still poorly understood how the THz emission amplitude and its bandwidth can be optimized. Here, we perform a systematic analysis of the THz emission from various
magnetic heterostructures. The dynamics of the
spin current is described by the semiclassical, superdiffusive
spin-transport model and the energy dependence of the
spin Hall effect of hot electrons is taken into account, leading to emission profiles for Co(2 nm)/Pt(4 nm)
bilayer in good agreement with experiment. To identify the optimal {conditions} for THz emission, {we study} the properties of the emitted THz wave profile by systematically varying the layer thicknesses of metallic
bilayers, their interfacial
spin-current transmission properties, their materials' dependence, and influence of the pump
laser-pulse width, allowing us to give optimization guidelines. We find that thin nonmagnetic layer thicknesses of 5-6 nm provide the largest bandwidth in the case of Co/Pt and that the peak frequency of the THz emission depends only on the geometry of the emitter and not on the
laser pulse width. The THz bandwidth {is conversely found to} depend on several factors such as exciting
laser pulse width, layers' thicknesses, and interface transmission-reflection properties, with the limitation that an increase in the bandwidth by tuning the interface properties comes with a trade-off in the energy efficiency of the emitter. Lastly, we propose a double pulse excitation protocol of a trilayer system that could provide broadband THz emission with a large bandwidth. {Our results contribute to establishing guidelines for optimizing spintronic THz generation.
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All authors Francesco Foggetti, Francesco Cosco, Peter M. Oppeneer, Henri Jaffrés, Niloufar Nilforoushan, Juliette Mangeney, Sukhdeep Dhillon
Materials Science · Cross-listed from physics.med-ph
Combining quasi-static and high frequency experiments for the viscoelastic characterization of brain tissue
Laura Ruhland, Nina Reiter, Silvia Budday et al. (+1 more)
Mechanical models of
brain tissue are a beneficial tool to simulate neurosurgical interventions, disease progression, or
brain development. However, the accuracy and predictive capacity of such a model relies on a precise experimental characterization of the tissue's mechanical behavior. Such a characterization is yet limited by inconsistent or contradictory experimental responses reported in the literature, particularly when measurements are performed in different time or length scales. Although
brain tissue has been extensively investigated in previous studies, the combination of experimental findings from different scales has received limited
attention. In this study, we combine ex vivo mechanical responses of porcine
brain tissue obtained at different time scales in a mechanical model. We investigated the mechanical behavior of three different
brain regions in the quasi-static domain with multi-modal large strain rheometer measurements and at high frequencies with
magnetic resonance elastography (MRE). A comparative analysis of the mechanical parameters obtained from both experimental techniques demonstrated consistent regional variations in the viscoelastic behavior across the two domains. However, the mechanical behavior changes from a higher elasticity in the quasi-static and low frequency domain to a dominating viscosity at high frequencies. Based on the quasi-static and the high frequency behavior, we calibrated a fractional Kelvin-Voigt model and consequently unified the two responses in a single mechanical model to obtain a comprehensive characterization of the tissue's mechanical behavior.
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All authors Laura Ruhland, Nina Reiter, Silvia Budday, Kai Willner
Disordered Systems and Neural Networks
Electrical conductivity of a random nanowire network: comparison of two-dimensional and quasi-three-dimensional models
Yuri Yu. Tarasevich and Andrei V. Eserkepov
Although the two-dimensional model of random networks of metallic nanowires or carbon nanotubes is widely used, it significantly overestimates the number of contacts between elements compared to quasi-three-dimensional models. This, within the mean-field approximation, leads to overestimates of the electrical conductivity, especially when the main contribution to the system's electrical conductivity comes from the contact resistances between the conductors. In the two-dimensional model, the system's electrical conductivity depends quadratically on the conductor density, whereas in the three-dimensional model, this dependence is linear. We propose a simple modification of a two-dimensional model, which can capture the saturation effect of the number of contacts per conductor in a real nanowire network.
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Statistical Mechanics
Spectral insights into active matter: Exceptional Points and the Mathieu equation
Horst-Holger Boltz and Thomas Ihle
We show that recent numerical findings of universal scaling relations in systems of noisy, aligning self-propelled particles by Kürsten [Kürsten, arXiv:2402.18711v2 [cond-mat.soft] (2025)] can robustly be explained by perturbation theory and known results for the Mathieu equation with purely imaginary parameter. In particular, we highlight the significance of a cascade of exceptional points that leads to non-trivial fractional scaling exponents in the singular-perturbation limit of high activity. Crucially, these features are rooted in the Fokker-Planck operator corresponding to free self-propulsion. This can be viewed as a dynamical phase transition in the dynamics of noisy active matter. We also predict that these scaling relations depend on the
symmetry of the
alignment interactions and discuss the relevance of this structure in the free propagation for self-
alignment and cohesion-type interactions.
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Mesoscale and Nanoscale Physics
Single-Shot Flow Spectroscopy of a Polariton Condensate: Kibble-Zurek and Kolmogorov-Like Scaling
Ivan Krasionov, Anton Putintsev, Maksim Kolker et al. (+3 more)
Quantized
vortices are fundamental topological excitations of
quantum fluids. We report single-shot interferometric measurements of spontaneous
vortex nucleation in a room-temperature organic
exciton-polariton condensate. From hundreds of independent realizations we find random
vortex-core positions and unbiased circulation, consistent with intrinsically
stochastic, unpinned defect formation. The mean
vortex number scales with pump power above threshold with an exponent consistent with Kibble-Zurek freeze-out in a driven-dissipative condensate. Using reconstructed phase maps we obtain single-shot flow fields, compute the incompressible component, and extract kinetic-energy spectra.
Vortex-containing realizations develop a robust Kolmogorov-like segment with Einc(k) proportional to k^(-5/3) over a finite k range, indicating the onset of turbulent spectral scaling in a
quantum fluid of light. These results establish single-shot access to phase and flow as a direct route to quantifying
stochastic defect formation and emerging
turbulence in polariton condensates.
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All authors Ivan Krasionov, Anton Putintsev, Maksim Kolker, Tamsin Cookson, Sergey Alyatkin, Pavlos G. Lagoudakis
Materials Science
Incorporating Gibbs free energy into interatomic potential fitting
Liangrui Wei and Yang Sun
We develop a method to fit high-temperature Gibbs free energy data for the development of interatomic potentials for atomic systems. The approach is based on
Hamiltonian thermodynamic integration, enabling the identification of suitable potential parameters such that the system's free energy matches a specified target. The method can be readily combined with conventional fitting techniques for properties such as elastic tensors and
liquid pair distribution functions. We validate the effectiveness of the approach using the Uhlenbeck-Ford model and embedded-atom method potentials for pure Ni phases and binary Fe1-xOx
liquids under high-pressure and high-temperature conditions. Our framework provides an efficient strategy for incorporating free energy into interatomic potential fitting.
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Soft Condensed Matter
A Toy Model for the Cycle Rank Dependence of Stretch at Break in Phantom Chain Network Simulations
Yuichi Masubuchi
The relationship between the topological architecture of
polymer networks and their macroscopic rupture remains a fundamental challenge in
polymer physics. Recent coarse-grained simulations have revealed that the dependence of stretch at break (\lambda_b) on node functionality and reaction conversion can be unified into a universal master curve when plotted against the cycle rank density (\xi). However, a theoretical derivation explaining this universality has been lacking. This study proposes a simple mechanical model to describe the \xi-dependence of \lambda_b. The
polymer network is modeled as a mechanical system consisting of a sequence of springs representing localized, highly stretched strands and the surrounding unstretched network. By relating the stiffness contrast between these regions to the network connectivity defined by \xi, an analytical expression for the stretch at break is derived: \lambda_b-1\propto\sfrac{\left(3\xi+6\right)}{\left(3\xi+2\right)}\ . The proposed model is validated against phantom chain simulations using both Gaussian and finite extensibility (FENE) springs. The theoretical prediction shows reasonable agreement with simulation data, providing a physical basis for the phenomenological universality observed in
polymer network rupture.
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Mesoscale and Nanoscale Physics
Spin quantum Hall transition on random networks: exact critical exponents via quantum gravity
Esteban Macías, Ilya Gruzberg and Eldad Bettelheim
We solve the problem of the
spin quantum Hall transition on random networks using a mapping to classical percolation that focuses on the boundary of percolating clusters. Using tools of two-dimensional
quantum gravity, we compute critical exponents that characterize this transition and confirm that these are related to the exponents for the regular (square) network through the KPZ relation. Our results demonstrate the relevance of the
geometric randomness of the networks and support conclusions of numerical simulations of random networks for the integer
quantum Hall transition.
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Statistical Mechanics
Noise-Assisted Metastability: From Lévy Flights to Memristors, Quantum Escape, and Josephson-based Axion Searches
Claudio Guarcello, Alexander A. Dubkov, Davide Valenti et al. (+1 more)
Many-body and complex systems, both classical and
quantum, often exhibit slow, nonlinear relaxation toward stationary states due to the presence of metastable configurations and environmental fluctuations. Nonlinear relaxation in a wide variety of natural systems proceeds through metastable states, which arise in condensed-matter physics as well as in fields ranging from cosmology and biology to high-energy physics. Moreover, noise-induced phenomena play a central role in shaping the dynamics of such systems far from
equilibrium. This review develops a unifying perspective centered on noise-assisted stabilization and the statistical properties of metastable dynamics. We first discuss escape processes driven by Lévy flights in smooth metastable potentials, emphasizing the emergence of nonmonotonic residence-time behavior. We then connect these concepts to
stochastic resistive switching in memristive devices, where noise-induced effects can enhance stability and reproducibility. We further examine driven dissipative
quantum bistability, showing how the interplay between external driving and system-environment coupling reshapes escape pathways and lifetimes. Finally, we outline how switching-time statistics in current-biased Josephson junctions can provide an experimentally accessible strategy for
axion detection, based on an
axion-induced resonant-activation signature.
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All authors Claudio Guarcello, Alexander A. Dubkov, Davide Valenti, Bernardo Spagnolo
Soft Condensed Matter
Small equatorial deformation of homogeneous spherical fluid vesicles
Andrés Solís-Cuevas and Pablo Vázquez-Montejo
We examine the reaction of a homogeneous spherical fluid vesicle to the force exerted by a rigid circular ring located at its equator in the linear regime. We solve analytically the linearized first integral of the Euler-Lagrange equation subject to the global constraints of fixed area and volume, as well as to the local constraint imposed by the ring. We determine the first-order perturbations to the generating curve of the spherical membrane, which are characterized by the difference of the radii of the membrane and the ring, and by a parameter depending on the physical quantities of the membrane. We determine the total force that is required to begin the deformation of the membrane, which gives rise to a discontinuity in the
curvature of the membrane across the ring.
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Materials Science
Turning Insulators into Accelerators: Deciphering the Interfacial Conductivity Boost in ZrO2-Li2ZrCl6 Composites through Machine Learning Molecular Dynamics Simulations
Boyuan Xu, Chen Qian, Liyi Bai et al. (+3 more)
Halide solid-state electrolytes have emerged as promising candidates for all-solid-state lithium batteries due to their high oxidative stability and deformability, yet their moderate ionic conductivity remains a bottleneck. While incorporating ionically insulating ZrO2 nanoparticles (Nat. Commun. 2023, 14, 2459) has been experimentally shown to enhance the ionic conductivity of Li2ZrCl6, the atomistic origin governing this interfacial phenomenon remains unclear. Here, we bridge the spatiotemporal gap in modeling complex
heterostructures by developing an accurate machine-learned force fields based on neuroevolution potential, enabling large-scale molecular dynamics simulations of ZrO2/Li2ZrCl6
heterostructures. By systematically investigating four representative low-
lattice-mismatch ZrO2/Li2ZrCl6 interfaces, we identify spontaneous interfacial amorphization driven by space-charge effects upon surface cleavage, trapping Li+ and leading to under-coordinated Li+ polyhedrons with pronounced
geometric distortion. These distorted amorphous interfacial regions exhibit markedly enhanced Li+ hopping activity, significantly outperforming the bulk
lattice, provided that local mobile Li+ inventory is not depleted by surface charge redistribution. This work establishes a computational framework for training validated machine-learned force fields for interfaces and provides mechanistic understandings of the interfacial conductivity boost in the
insulator-conductor composites, guiding the rational design of electrolytes toward next-generation solid-state batteries.
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All authors Boyuan Xu, Chen Qian, Liyi Bai, Chenlu Wang, Feng Ding, Qisheng Wu
Superconductivity
Electronic Origin of Density Wave Orders in a Trilayer Nickelate
Jiangang Yang, Jun Zhan, Taimin Miao et al. (+24 more)
The discovery of superconductivity in Ruddlesden-Popper nickelates has established a new frontier in the study of high-temperature
superconductors. However, the underlying pairing mechanism and its relationship to the material's electronic and
magnetic ground states remain elusive. Since unconventional superconductivity often emerges from a complex interplay of
magnetic correlations, elucidating the
magnetic ground state of the nickelates at ambient pressure is crucial for understanding the emergence of superconductivity under high pressure. Here, we combine high-resolution angle-resolved photoemission spectroscopy with tight-binding model simulation to investigate the electronic structure of the representative trilayer Ruddlesden-Popper nickelate La$_4$Ni$_3$O$_{10}$. We provide the first experimental evidence of band splitting induced by interlayer coupling and further resolve the momentum-dependent density wave gap structures along all the
Fermi surfaces. Our findings identify the mirror-selective
Fermi surface nesting as the origin of the interlayer
antiferromagnetic spin density wave and demonstrate the dominant role of Ni-3d$_{z^2}$ orbitals in the low-energy physics of La$_4$Ni$_3$O$_{10}$. These results provide a fundamental framework for understanding the
magnetic interactions and high-temperature superconductivity mechanism in the Ruddlesden-Popper nickelate family.
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All authors Jiangang Yang, Jun Zhan, Taimin Miao, Mengwu Huo, Qichen Xu, Yinghao Li, Yuyang Xie, Bo Liang, Neng Cai, Hao Chen, Wenpei Zhu, Mingkai Xu, Shenjin Zhang, Fengfeng Zhang, Feng Yang, Zhimin Wang, Qinjun Peng, Hanqing Mao, Xintong Li, Zhihai Zhu, Guodong Liu, Zuyan Xu, Jiangping Hu, Xianxin Wu, Meng Wang, Lin Zhao, X. J. Zhou
Strongly Correlated Electrons
Interaction induced topological magnon in electron-magnon coupled systems
Kosuke Fujiwara and Takahiro Morimoto
We theoretically study the emergence of topological
magnons in electron-
magnon coupled systems. The
magnon dispersion in a ferromagnet usually possesses an effective time reversal
symmetry in the absence of Dzyaloshinskii-Moriya (DM) interaction, preventing the appearance of topological
magnons. When a
spin system is coupled to itinerant electrons, we find that the
magnon band structure of the
spin system experiences time-reversal
symmetry breaking with the electron-
magnon interaction via the exchange coupling, where topological
magnons arise without requiring strong DM. Specifically, we consider a
heterostructure consisting of a
ferromagnetic insulator and a transition metal dichalcogenide (TMD) monolayer and investigate topological gap opening in
magnon bands. Our findings reveal that even trivial ferromagnets can host topological
magnons via coupling to itinerant electronic systems.
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Strongly Correlated Electrons
Understanding the sign problem from an exact Path Integral Monte Carlo model of interacting harmonic fermions
Siu A. Chin
This work shows that the recently discovered operator contraction identity for solving the discreet Path Integral of the harmonic oscillator can be applied equally to
fermions in any dimension. This then yields an exactly solvable model for studying the sign problem where the Path Integral Monte Carlo energy at any time step for any number of
fermions is known analytically, or can be computed numerically. It is found that the sign problem is primarily a property of the free
fermion propagator, but repulsive/attractive pairwise interaction can shift the sign problem to larger/smaller imaginary time but does not make it more severe than the non-interacting case. More surprisingly, one can prove analytically that the first closed-shell state in $D$ dimension, with $n=D+1$
fermion, has no sign problem at large imaginary time. Direct numerical simulations confirm that this is also true for higher closed-shell states in two and three-dimension. Fourth-order and newly found variable-bead
algorithms are used to compute ground state energies of
quantum dots with up to 110 electrons and compared to results obtained by modern neural networks.
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Strongly Correlated Electrons · Cross-listed from physics.optics
Strong Coupling Between RF Photons and Plasmons of Electrons on Liquid Helium
Asher Jennings, Ivan Grytsenko, Thomas Giovansili et al. (+6 more)
Plasmons, arising from the collective motion of electrons, can interact strongly with electromagnetic fields or
photons; this capability has been exploited across a broad range of applications, from chemical reactivity to biosensing. Recently, there has been growing interest in plasmons for applications in
quantum information processing. Electrons floating on
liquid helium provide an exceptionally clean, disorder-free system and have emerged as a promising platform for this purpose. In this work, we establish this system as a tunable plasmon-
photon hybrid platform. We demonstrate strong coupling between floating-electron plasmons and
radio-frequency (RF)
photons confined in an LC resonator. Time-resolved measurements reveal coherent oscillatory energy exchange between the plasmonic and photonic modes, providing direct evidence of their coherent coupling. These results represent a step towards cavity
quantum electrodynamics with a floating-electron plasmon coupled to a resonator. Furthermore, the LC resonator serves as a sensitive probe of electron-on-helium physics, enabling the observation of the Wigner
crystal transition and a quantitative study of the temperature-dependent plasmon decay arising from ripplon-induced scattering.
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All authors Asher Jennings, Ivan Grytsenko, Thomas Giovansili, Itay Josef Barabash, Oleksiy Rybalko, Yiran Tian, Jun Wang, Hiroki Ikegami, Erika Kawakami
Materials Science
Thermal and Microstructural Simulations of Photonic Sintering of Oxide Ceramics: A Two-Scale Scheme
Junlong Ma, Yangyiwei Yang, Julian N. Ebert et al. (+2 more)
Photonic sintering (PS) offers an ultra-fast, contact-free alternative to conventional sintering and has demonstrated its potential for enhancing the sinterability of acceptor-doped barium zirconate (BZY) ceramics. However, a central challenge in the PS process lies in achieving precise control over thermal self-stabilization in the presence of complex microstructural effects arising from photonic-ray–induced thermal profiles. To elucidate the interplay among thermal fields, microstructural
evolution, and PS process parameters, this study establishes a two-scale, non-isothermal simulation framework. The framework integrates macroscopic heat-transfer simulations, incorporating effective heat conduction and photonic-ray–induced volumetric heating in the porous media, with microscopic non-isothermal phase-field sintering simulations that resolve microstructure
evolution under local thermal profile. Scale bridging is achieved through a temperature field transferring and mapping that satisfies Hill-Mandel condition between the macroscopic and microscopic simulations, while maintaining synchronization between their asynchronous time-stepping schemes. After calibrating model parameters against experimental measurements, the framework successfully reproduces the experimentally observed porosity inhomogeneity along the sample depth. The influence of enhanced localized mass transport is further examined through a parametric investigation of surface and grain boundary diffusivities. Overall, the proposed framework demonstrates its feasibility and physical interpretability in establishing process-microstructure relationships for the scalable fabrication of high-performance protonic ceramics.
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All authors Junlong Ma, Yangyiwei Yang, Julian N. Ebert, Wolfgang Rheinheimer, Bai-Xiang Xu
Strongly Correlated Electrons
Electronic band structure, phonon dispersion, and magnetic triple-q state in GdGaI
Tatsuya Kaneko, Ryota Mizuno, Shu Kamiyama et al. (+2 more)
We theoretically investigate the physical properties of the
magnetic van der Waals material GdGaI. Using first-principles calculations, we compute the
phonon dispersion of GdGaI and show no imaginary
phonons, suggesting that
phonon-driven phase transitions are unlikely to occur in GdGaI. Our band calculation reveals that the electronic bands near the
Fermi energy are composed of Gd 5d and Ga 4p orbitals. We construct a tight-binding model that incorporates the Gd 5d and Ga 4p orbitals to investigate the
magnetic structure. We introduce Kondo coupling between electrons in Gd 5d orbitals and localized
spins in Gd 4f orbitals and present the modified band structure when localized
spins form a
magnetic order characterized by three q vectors that connect the valence and conduction bands. We discuss the origin of the
spin order based on the Ruderman-Kittel-Kasuya-Yosida mechanism and suggest that Coulomb interactions acting on electrons near the
Fermi level can contribute to the ordering of localized
spins.
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All authors Tatsuya Kaneko, Ryota Mizuno, Shu Kamiyama, Hideo Miyamoto, Masayuki Ochi