Mesoscale and Nanoscale Physics
Non-Hermitian trapping of Dirac exciton-polariton condensates in a perovskite metasurface
Mikhail Masharin, Igor Chestnov, Andrey Bochin et al. (+9 more)
Massless Dirac particles avoid trapping due to their exceptional tunneling properties manifested in the so-called Klein paradox. This conclusion stems from the conservative treatment, but so far, it has not been extended to a non-Hermitian framework. Recently, driven-dissipative bosonic condensation of Dirac
exciton-polaritons was demonstrated in metasurface waveguides. Here, we report an experimental observation of spatial binding and energy quantization of Dirac
exciton-polaritons in a halide perovskite metasurface. A combination of spatially profiled nonresonant optical excitation and
exciton-polariton interaction forms an effective non-Hermitian complex potential responsible for the observed effect. In the case of tightly focused pump spots spanning from 9 to 17~$\mu$m, several bound states simultaneously achieve macroscopic occupation, constituting a multi-mode bosonic condensation of
exciton-polaritons. Our theoretical analysis based on the driven-dissipative extension of the Dirac equation reveals that the non-Hermitian character of the effective trap allows for confinement even in the case of the gapless Dirac-like photonic dispersion, both above and below the energy of the dispersion crossing.
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All authors Mikhail Masharin, Igor Chestnov, Andrey Bochin, Pavel Kozhevin, Vanik Shahnazaryan, Alexey Yulin, Ivan Iorsh, Xuekai Ma, Stefan Schumacher, Sergey Makarov, Anton Samusev, Anton Nalitov
Mesoscale and Nanoscale Physics
Unconventional bright ground-state excitons in monolayer TiI$_2$ from first-principles calculations
Franz Fischer, Carl Emil Mørch Nielsen, Marta Prada et al. (+1 more)
Based on ab initio screened configuration interaction calculations we find that TiI$_2$ has a bright
exciton ground state and identify two key mechanisms that lead to this unprecedented feature among transition metal dichalcogenides. First, the
spin-orbit induced conduction band splitting results in optically allowed
spin-
alignment for electrons and holes across a significant portion of the Brillouin zone around the $\mathbf{K}$-valley, avoiding band crossings seen in materials like monolayer MoSe$_2$. Second, a sufficiently weak exchange interaction ensures that the bright
exciton remains energetically below the dark
exciton state. We further show that the bright
exciton ground state is stable under various mechanical strains and that trion states (charged
excitons) inherit this bright ground state. Our findings are expected to spark further investigation into related materials that bring along the two key features mentioned, as bright ground-state
excitons are crucial for applications requiring fast radiative recombination.
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All authors Franz Fischer, Carl Emil Mørch Nielsen, Marta Prada, Gabriel Bester
Superconductivity · Cross-listed from physics.ins-det
Advanced microwave SQUID multiplexer model incorporating readout power effects and Josephson junction inhomogeneities
Martin Neidig, Mathias Wegner and Sebastian Kempf
We present an advanced model for describing the readout power dependence of the resonance characteristics of a microwave SQUID multiplexer. Our model proves valid for SQUID screening parameters up to $\beta_\mathrm{L}<1$, hence covering the full range of practically relevant design parameters. We demonstrate that our model significantly improves agreement with experimental data compared to the existing models, thereby enabling optimization beyond the previously accessible parameter space. Moreover, our model supports non-sinusoidal current-phase relations of the rf-SQUID's Josephson junction, allowing, for the first time, for the modeling of devices based on Josephson tunnel junctions with inhomogeneous tunnel barriers. We show that the effects of such inhomogeneities are qualitatively similar to, yet distinct from, those of the screening parameter, making their inclusion essential for accurate characterization. Incorporating these effects yields great improved agreement with measurements, even at readout power conditions well beyond typical operating parameters.
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Soft Condensed Matter
Self-Trapping of Microorganisms Steering Toward their Own Trail
Aymeric Lutier, Frédéric van Wijland and Jean-Baptiste Fournier
Active matter systems comprise self-propelled particles that move on a substrate while leaving chemical trails that influence other particles through chemotaxis (e.g., slime-depositing bacteria). Orientational chemotaxis manifests as a torque that steers the particle toward the chemical gradient. As each particle is coupled to its own trail, the dynamics exhibits an instability: when the particle gently diffuses, it abruptly transitions to trajectories with a radius of
curvature comparable to its own size, becoming apparently trapped. We argue that, contrary to intuition, this trajectory instability occurs for any chemotactic coupling strength. Depending on the coupling regime, this arises either through a potential-barrier first-passage problem or from a rare event analysis.
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Disordered Systems and Neural Networks
Unified theory of local integrals of motion
Ben Craps, Oleg Evnin, Dmitry Kovrizhin et al. (+1 more)
Conservation laws are of paramount importance in our understanding of classical and
quantum dynamics. Here, we present a general framework for constructing exact
quantum integrals of motion with the desired locality and
quantum numbers, which will be illustrated for the case of many-body-localization (MBL). The latter has been understood theoretically in terms of the existence of an extensive number of local integrals of motion (LIOMs). Using our approach, we show that one can express the task of finding LIOMs as an optimization problem. For some specifications, this problem surprisingly connects to the question of finding classical ground states of
spin-glass models. Our work unifies previous results obtained in the MBL context and reveals intriguing connections between many-body localization,
spin-glass physics, and constrained optimization problems.
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All authors Ben Craps, Oleg Evnin, Dmitry Kovrizhin, Gabriele Pascuzzi
Strongly Correlated Electrons
Single-crystal growth, structural characterization, and physical properties of a decorated square-kagome antiferromagnet KCu$_7$TeO$_4$(SO$_4$)$_5$Cl
Jingjing Jing, Andreas Eich, Yiqiu Liu et al. (+9 more)
The square-kagome
lattice, composed of two-dimensional corner-sharing triangles, provides a novel platform for studying frustrated magnetism. However, material realizations of the square-kagome
lattice remain scarce. Here, we report the single-
crystal growth, structural characterization,
magnetic and electric properties of KCu$_7$TeO$_4$(SO$_4$)$_5$Cl, a nabokoite compound featuring a distorted and decorated square-kagome
lattice. Weak anomalies near 4 K are observed in both magnetization and specific heat, indicating the onset of a
magnetic transition.The formation of a long-range
antiferromagnetic state below 4.5 K is further confirmed by $^{35}$Cl
nuclear magnetic resonance (NMR) measurements.
Magnetic susceptibility data reveal nearly isotropic Curie-Weiss temperatures ($\sim-145$ K) and $g$-factors ($\sim2.4$) for both in-plane and out-of-plane
magnetic fields. Moreover, we observe two successive ferroelectric transitions at $T_\mathrm{FE1}\sim30$ K and $T_\mathrm{FE2}\sim27$ K, driven by inversion-
symmetry breaking, most likely associated with distortions in the Cu2O$_4$Cl$_1$ pyramids and the adjacent SO$_4$ tetrahedra. These results suggest that a three-dimensional model incorporating interlayer couplings via decorating Cu2 sites is essential for capturing the
magnetic and electric behaviors in KCu$_7$TeO$_4$(SO$_4$)$_5$Cl.
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All authors Jingjing Jing, Andreas Eich, Yiqiu Liu, Lunhua He, Aifeng Wang, Yisheng Chai, Young Sun, Yi Cui, Weiqiang Yu, Xinrun Mi, Michael Merz, Mingquan He
Materials Science
Structural Phase Transition and Cooperative Luminescence in K3Yb(PO4)2:Eu3+ for Multimodal Down-shifting and Up-converting Luminescence Thermometry
Anam Javaid, Maja Szymczak, Damian Szymanski et al. (+1 more)
To develop a more universal luminescent thermometer that provides both high relative sensitivity and the ability to measure temperature across different spectral ranges and excitation wavelengths, the K3Yb(PO4)2:Eu3+ system was proposed in this work. It was demonstrated that this material undergoes a structural phase transition from the monoclinic to the hexagonal phase above 450 K. This transition enabled the construction of a ratiometric, phase-transition-based thermometer utilizing the luminescence intensity ratio of Stark lines of Eu3+ and Yb3+ ions, which exhibit SRmax values of 4.2% K^-1 and 1.15% K^-1, respectively. Moreover, increasing the Eu3+ ion concentration was shown to raise the phase transition temperature, thereby shifting the thermal operating range of both luminescent thermometers. Under 980 nm excitation, K3Yb(PO4)2:Eu3+ exhibits both cooperative luminescence from Yb3+ pairs and up-conversion emission from Eu3+ ions. Increasing the Eu3+ concentration enhances the Eu3+ luminescence intensity relative to the cooperative luminescence of Yb3+ pairs, resulting in a change in the emitted light color. The difference in the thermal quenching behavior of these two signals further enabled the development of a ratiometric thermometer with SRmax = 0.58% K^-1. These findings identify K3Yb(PO4)3:Eu3+ as a promising candidate for
multimodal temperature sensing.
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All authors Anam Javaid, Maja Szymczak, Damian Szymanski, Lukasz Marciniak
Materials Science
Magnetic properties of molecular beam epitaxy-grown ultrathin Cr2Ge2Te6 films down to monolayer limit on Si substrates
Pengfei Ji, Ruixuan Liu, Tianchen Zhu et al. (+13 more)
Cr2Ge2Te6, a prototypical van der Waals
ferromagnetic semiconductor, have attracted significant interest for its potential applications in high-performance spintronics. However, the
magnetic ground state of monolayer Cr2Ge2Te6 remains elusive due to fragile and irregular-shaped thin flake samples with weak
magnetic signals. Here, we successfully grow uniform
ferromagnetic Cr2Ge2Te6 films down to monolayer by molecular beam epitaxy. By exploiting a self-limiting growth mode, we achieve synthesis of uniform monolayer Cr2Ge2Te6 films across entire millimeter-scale Si substrates. Through a combination of superconducting
quantum interference device magnetometry and anomalous
Hall effect measurements, we establish that monolayer Cr2Ge2Te6 exhibits intrinsic ferromagnetism with perpendicular
magnetic anisotropy below ~10 K, albeit with strong
magnetic fluctuations characteristic of its two-dimensional nature. Furthermore, a systematic thickness-dependent study reveals a crossover from this fluctuation-dominated two-dimensional magnetism turns into conventional long-range
ferromagnetic order as the film thickness increases. Our work not only definitively establishes the intrinsic
ferromagnetic ground state of monolayer Cr2Ge2Te6, but also provides a scalable, silicon-compatible route for preparing the two-dimensional magnet for future spintronic or
quantum devices.
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All authors Pengfei Ji, Ruixuan Liu, Tianchen Zhu, Jinxuan Liang, Yang Chen, Yitian Tong, Yunhe Bai, Zuhan Geng, Fangting Chen, Yunyi Zang, Xiyu Hong, Jiatong Zhang, Luyi Yang, Qi-Kun Xue, Ke He, Xiao Feng
Superconductivity
Study of fluctuation conductivity in YBa$_2$Cu$_3$O$_7$–$\delta$ films in strong magnetic fields
E. V. Petrenko, L. V. Omelchenko, Yu. A. Kolesnichenko et al. (+4 more)
We report the effect of the ab-plane
magnetic field $B$ up to $8\,\mathrm{T}$ on the resistivity $\rho(T)$ and fluctuation conductivity $\sigma'(T)$ in YBa$_2$Cu$_3$O$_{7-\delta}$ thin films. As expected, up to $\sim 2.5\,\mathrm{T}$ the
magnetic field monotonously increases $\rho$, the width of the resistive transition $\Delta T_c$, and the coherence length along the $c$ axis, $\xi_c(0)$, but decreases both $T_c$ and the range of superconducting (SC) fluctuations $\Delta _{\mathrm{fl}}$. The fluctuation conductivity exhibits a crossover at characteristic temperature $T_0$ from the 3D Aslamazov–Larkin (AL) theory near $T_c$ to the 2D fluctuation theory of Maki–Thompson (MT). However, at $B = 3\,\mathrm{T}$, the MT term is completely suppressed, and above $T_0$ $\sigma'(T)$ is unexpectedly described by the fluctuation contribution of 2D AL, suggesting the formation of a two-dimensional
vortex lattice in the film under the action of a
magnetic field. At the same time, $\Delta T_{\mathrm{fl}}$ sharply increases by a factor of about 7, and $\xi_c(0)$ demonstrates a very unusual dependence on $T_c$ when $B$ increases above $3\,\mathrm{T}$. Our results demonstrate the possibility of the formation of a
vortex state in YBCO and its
evolution with increasing $B$.
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All authors E. V. Petrenko, L. V. Omelchenko, Yu. A. Kolesnichenko, N. V. Shytov, K. Rogacki, D. M. Sergeyev, A. L. Solovjov
Superconductivity
Checkerboard-type Zhang-Rice States in Overdoped Cuprate Superconductors
Xiongfang Liu, Kun Han, Yan Peng et al. (+13 more)
Cuprate
superconductors remain central to condensed matter physics due to their technological relevance and unconventional, incompletely understood electronic behavior. While the canonical phase diagram and low-energy models have been shaped largely by studies of underdoped and moderately doped cuprates, the overdoped regime has received comparatively limited
attention.Here, we track the
evolution of the electronic structure from optimal to heavy overdoping in La2-xSrxCuO4(LSCO) using broadband optical spectroscopy across x=0.15-0.60. The measured spectral changes–including the redistribution of Zhang-Rice-related spectral weigh–are in qualitative agreement with determinant
quantum Monte Carlo simulations of the three-orbital Emery model, which together indicate a pronounced reconstruction of the electronic structure beyond hole concentrations x>0.2. Guided by these observations, we propose a spontaneous checkerboard-type Zhang-Rice electronic configuration that captures the coexistence of itinerant and localized carriers characteristic of the heavily overdoped state. Our results refine the doping-dependent Zhang-Rice-based framework for cuprates, illuminate how correlations persist deep into the overdoped regime, and provide new constraints on microscopic mechanisms of high-temperature superconductivity, with broader implications for correlated transition-metal
oxides.
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All authors Xiongfang Liu, Kun Han, Yan Peng, Yuanjie Ning, Jing Wu, Zhaoyang Luo, Difan Zhou, Zhigang Zeng, Qian He, Chuanbing Cai, Mark. B. H. Breese, Ariando Ariando, Chi Sin Tang, George A. Sawatzky, Mi Jiang, Xinmao Yin
Soft Condensed Matter
High-throughput characterization of snap-through stability boundaries of bistable beams in a programmable rotating platform
Eduardo Gutierrez-Prieto, Gilad Yakir and Pedro M. Reis
We introduce a high-throughput platform that enables simultaneous, parallel testing of six bistable beams via programmable motion of a rotating disk. By prescribing harmonic angular dynamics, the platform explores the phase space of angular velocity and acceleration $(\Omega,\,\dot{\Omega})$, producing continuously varying centrifugal and Euler force fields that act as tunable body forces in our specimens. Image processing extracts beam kinematics with sub-pixel accuracy, enabling precise identification of snap-through events. By testing six beams in parallel, the platform allows systematic variation of beam thickness, pre-compression, tilt angle, and clamp orientations across 65 distinct configurations, generating 23,400 individual experiments. We construct stability boundaries and quantitatively parameterize them as
parabolic functions, characterized by a vertical offset and a
curvature parameter. Tilt angle provides the most robust mechanism for tuning the
curvature parameter, while beam thickness and pre-compression modulate vertical offset. Modal decomposition analysis reveals that antisymmetric clamp configurations can trigger mode switching, in which competing
geometric and inertial effects drive transitions through different deformation pathways. Our work establishes a scalable experimental framework for high-throughput characterization of dynamic nonlinear instabilities in mechanics. The complete experimental
dataset is made publicly available to support data-driven design and machine learning models for nonlinear mechanics with applications to bistability-based metamaterials, mechanical
memory, and electronics-free sensing systems.
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Mesoscale and Nanoscale Physics
Kerr effect induced by exchange interaction of electrons separated by a tunnel barrier in a double quantum well
V.K. Kalevich, K.V. Kavokin, M.M. Afanasiev et al. (+4 more)
In a structure with two tunnel-coupled
quantum wells of different widths, the
spin dynamics resulting from resonant pulsed optical pumping of the narrow-well
exciton includes the wide-well electron magnetization dynamics. Our analysis shows that the effect is driven by electron exchange between narrow-well
excitons and
spin-polarized electrons in the wide well. A theoretical model of the
spin Kerr effect has been developed accounting for the interwell electron
spin exchange. In the studied double-well structure with CdTe and Cd$_{0.98}$Mn$_{0.02}$Te
quantum wells and a well-separating barrier thickness of 5 monolayers (1.6 nm), the model accurately describes the experimental results and allows us to estimate the interwell electron exchange constant as $\delta_{e} \approx 0.9\times10^{-15}~\textrm{eV}~\textrm{cm}^{2}$.
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All authors V.K. Kalevich, K.V. Kavokin, M.M. Afanasiev, B.F. Gribakin, M.I. Kuzmenko, G. Karczewski, Yu.G. Kusrayev
Materials Science
Effect of cold rolling strain on the microstructural evolution in equimolar MoNbTaTiZr refractory complex concentrated alloy: Comprehensive characterization
Andrea Skolakova, Haruka Katayama, Pavel Lejcek et al. (+8 more)
This work presents a pilot study on a strained complex concentrated
alloy based on refractory elements: MoNbTaTiZr. Initially, the as-cast and homogenization-annealed conditions were characterized. After casting, the
alloy consists of two solid solutions with BCC 1 and BCC 2
crystal structures. Homogenization annealing promotes the growth, ordering, and refinement of the BCC 2 phase. TEM and AES analyses indicate possible Zr segregation at grain boundaries in the as-cast state. In contrast, annealing followed by cooling results in the formation of Ti-Zr-based particles without segregation. Subsequently, the annealed
alloy was cold-rolled, and its microstructure was investigated. During rolling, grain fragmentation occurs within the structure. In addition to the two BCC solid solutions, a phase with an FCC
crystal structure is identified after rolling. Its composition corresponds to the Zr2Ta phase, which is a Laves phase of the A2B type. Rotational relationships, relatively rare in rolled materials with BCC structures, are identified. The texture components found after 10% rolling deformation are related to that present after 20% deformation by a 45 degrees <110> rotation, and this component is related to that appearing after 30% deformation by a 20 degrees <100> rotation. However, no distinct rolling texture or clear texture development was observed, although some mutual relationships among preferred orientations can be identified. Schmid and Taylor factor maps demonstrate that, despite deformation, the
alloy remains capable of further strain accumulation and plastic deformation. Twinning is also observed after rolling, which may be beneficial, as deformation twinning contributes to improved ductility in the
alloy.
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All authors Andrea Skolakova, Haruka Katayama, Pavel Lejcek, Orsolya Molnarova, Sadahiro Tsurekawa, Petr Vertat, Jan Duchon, Jaroslav Cech, Petr Svora, Ondrej Ekrt, Jan Pinc
Superconductivity
Influence of strong electron irradiation on fluctuation conductivity and pseudogap in YBa$_2$Cu$_3$O$_7$–$\delta$ single crystals
A. L. Solovjov, K. Rogacki, N. V. Shytov et al. (+4 more)
The effect of high-energy electron irradiation on the temperature dependences of the resistivity $\rho(T)$, fluctuation conductivity (FLC), and pseudogap (PG) $\Delta^{*}(T)$ of YBa$_2$Cu$_3$O$_7$–$\delta$ (YBCO) single
crystals without twins was studied. Irradiation causes a linear increase in $\rho(T)$ and a decrease in the superconducting transition temperature $T_c$ with dose $\phi$. For small $\phi$, the reduction of $T_c$ follows the Abrikosov–Gorkov (AG) pair-breaking theory, while for large $\phi$ it is described by the Emery–Kivelson (EK) model, where
quantum phase fluctuations dominate. At $\phi_3 = 2.5 \times 10^{19}$ e/cm$^2$, which corresponds to the AG–EK crossover, the spacing between CuO$_2$ planes $d_{01}$, the coherence length $\xi_c(0)$, and the fluctuation region $T_{\mathrm{fl}}$ increase sharply, and the two-dimensional Maki–Thompson (2D–MT) contribution is replaced by the Aslamazov–Larkin (2D–AL) term. Surprisingly, no signatures of the crossover appear in $\rho(\phi)$ or $T_c(\phi)$. At the same $\phi_3$, a sharp rise in the pseudogap opening temperature $T^{*}$ and in $\Delta^{*}$ indicates a possible reduction of the density of states. With further increase in $\phi$, both PG parameters and their energy scale decrease markedly, and $\Delta^{*}(T)$ acquires an unusual form. However, at $\phi_5 = 5.6 \times 10^{19}$ e/cm$^2$, the temperature dependences of FLC and PG again show behavior typical of well-structured YBCO, regardless of defect density.
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All authors A. L. Solovjov, K. Rogacki, N. V. Shytov, E. V. Petrenko, L. V. Bludova, A. Chroneos, R. V. Vovk
Statistical Mechanics
Single particle dynamical signature of topology induced by single mode cavities in Su-Schrieffer-Heeger chain
Fabrizio Pavan, Grazia Di Bello, Giulio De Filippis et al. (+1 more)
Witnessing and tracking topological phase transitions induced by interactions with the environment is a crucial challenge. Among the various experimental approaches to detect topological properties, the Mean
Chiral Displacement (MCD) has emerged as a powerful bulk probe in one-dimensional
chiral systems, allowing the extraction of the topological invariant from single-particle dynamics. Here we study the dynamics of a single particle in a one-dimensional Su-Schrieffer-Heeger chain coupled to multiple cavity modes via inter-
cell hopping terms, focusing on the out-of-
equilibrium behavior of the MCD. We show that, whenever the frequency is larger than the static hopping amplitudes, the coupling induces a discontinuous jump in the MCD, already at small times, signaling that such a coupling also leaves a signature in the survival edge probability when the dynamics are initialized at one of the two edges. For frequencies comparable to the static hopping amplitudes, topological order competes with dissipative effects, which makes the MCD behave smoothly, retaining information about the driven-dissipative
topology.
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All authors Fabrizio Pavan, Grazia Di Bello, Giulio De Filippis, Carmine Antonio Perroni
Mesoscale and Nanoscale Physics
Controlling Skyrmion Lattices via Strain: Elongation, Tilting, and Collapse Mechanisms
Haijun Zhao, Tae-Hoon Kim, Lin Zhou et al. (+1 more)
This study establishes a comprehensive framework for the three-dimensional strain control of
magnetic skyrmion strings. We integrate analytical modeling, micromagnetic simulations, and in situ Lorentz transmission electron microscopy experiments to demonstrate that externally applied strain is a powerful stimuli for manipulating three-dimensional
magnetic skyrmion strings. Analytical models predict that strain induces both elongation and bidirectional tilting of skyrmion strings in bulk systems, a finding corroborated by numerical simulations. These simulations further reveal that strain drives the system from fragmented multi-domain states toward unified single-domain configurations and facilitates skyrmion string rupture via bobber formation at critical strain levels. The collapse of the skyrmion
lattice exhibits a temperature-dependent character, shifting from first-order to second-order behavior near the critical temperature $T_c$. Reducing sample thickness significantly increases the critical strain required for annihilation due to the suppression of tilting. Experimental validation on a $\text{Co}_8\text{Zn}_{8.5}\text{Mn}_{3.5}$ sample confirms strain-induced elongation and subsequent collapse into a conical phase via anti-cluster formation, directly implicating strain-modulated Dzyaloshinskii-Moriya interaction (DMI) as the primary mechanism in this system, over magnetocrystalline anisotropy. These findings provide a mechanistic understanding of strain-mediated control in three-dimensional
magnetic systems, demonstrating its feasibility for energy-efficient spintronic applications.
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All authors Haijun Zhao, Tae-Hoon Kim, Lin Zhou, Liqin Ke
Materials Science
Transport Novelty Distance: A Distributional Metric for Evaluating Material Generative Models
Paul Hagemann, Simon Müller, Janine George et al. (+1 more)
Recent advances in generative machine learning have opened new possibilities for the discovery and design of novel materials. However, as these models become more sophisticated, the need for rigorous and meaningful evaluation metrics has grown. Existing evaluation approaches often fail to capture both the quality and novelty of generated structures, limiting our ability to assess true generative performance. In this paper, we introduce the Transport Novelty Distance (TNovD) to judge generative models used for materials discovery jointly by the quality and novelty of the generated materials. Based on ideas from Optimal Transport theory, TNovD uses a coupling between the features of the training and generated sets, which is refined into a quality and memorization regime by a threshold. The features are generated from
crystal structures using a graph neural network that is trained to distinguish between materials, their augmented counterparts, and differently sized supercells using contrastive learning. We evaluate our proposed metric on typical toy experiments relevant for
crystal structure prediction, including memorization, noise injection and
lattice deformations. Additionally, we validate the TNovD on the MP20 validation set and the WBM substitution
dataset, demonstrating that it is capable of detecting both memorized and low-quality material data. We also
benchmark the performance of several popular material generative models. While introduced for materials, our TNovD framework is domain-agnostic and can be adapted for other areas, such as images and molecules.
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All authors Paul Hagemann, Simon Müller, Janine George, Philipp Benner
Soft Condensed Matter
Breaking the Logarithmic Barrier: Activity-Induced Recovery of Phase Separation Dynamics in Confined Geometry
Preethi M, Parameshwaran A and Bhaskar Sen Gupta
Phase separation in confined environments is a fundamental process underlying geological flows, porous filtration, emulsions, and intracellular organization. Yet, how confinement and activity jointly govern coarsening kinetics and interfacial morphology remains poorly understood. Here, we use large-scale molecular dynamics simulations to investigate vapor-
liquid phase separation of passive and active fluids embedded in complex porous media. By generating porous host structures via a freeze-quench protocol, we systematically control the average pore size and demonstrate that confinement induces a crossover from the Lifshitz-Slyozov power-law growth to logarithmically slowed coarsening, ultimately arresting domain
evolution. Analysis of correlation functions and structure factors reveals that confined passive systems exhibit fractal interfaces, violating Porod's law and indicating rough morphological arrest. In contrast, introducing self-propulsion dramatically changes the coarsening pathway: activity restores smooth interfaces, breaks the confinement-induced scaling laws, and drives a transition from logarithmic to ballistic domain growth at high activity levels. Our findings reveal an activity-controlled mechanism to overcome
geometric restrictions and unlock coarsening in structurally heterogeneous environments. These insights establish a unifying framework for nonequilibrium phase transitions in porous settings, with broad relevance to active colloids, catalytic media, and biologically crowded systems, where living matter routinely reorganizes within
geometric constraints to sustain function.
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Strongly Correlated Electrons
Transport properties and thermopower of the spinful Sachdev-Ye-Kitaev dot
Daniele Morotti, Marco Uguccioni and Luca Dell'Anna
We study the electric and thermoelectric transport through a spinful complex Sachdev-Ye-Kitaev (SYK)
quantum dot coupled to metallic leads, forming a N-SYK-N junction, by the Keldysh field theory approach. Unlike traditional
equilibrium approaches, our formulation treats the system as an open, interacting
quantum conductor under non-
equilibrium conditions, without resorting to the replica trick. Starting from the exact Keldysh-Dyson equations, we derive analytical results for the tunneling and zero-temperature limits and perform a numerical analysis in the linear-response regime. We characterize the dependence of conductance, thermoelectric coefficient, and Seebeck effect on the particle-hole asymmetry parameter and coupling strength to the leads. Our results reveal distinctive non-
Fermi liquid signatures of the SYK model in transport properties and identify coupling regimes where thermoelectric effects are enhanced, suggesting experimentally accessible fingerprints of SYK physics in mesoscopic systems.
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Disordered Systems and Neural Networks
Spontaneous symmetry breaking on graphs and lattices
Oleg Evnin
Spontaneous
symmetry breaking is a cornerstone of modern physics, defining a wealth of phenomena in condensed-matter and high-energy physics, and beyond. It requires an infinite number of degrees of freedom, and even then, for continuous
symmetries, it only works if the spatial dimension is not too low, following the classic results of Coleman, Hohenberg, Mermin and Wagner. While usually discussed in the context of
quantum and statistical field theories, and in particular, effective field theories, there are advantages in addressing the same kind of phenomena on discrete
geometric structures rather than conventional
manifolds. When the space is discretized into a
lattice, a lucid picture of conventional spontaneous
symmetry breaking springs up, with the ultraviolet issues of continuum
quantum field theory out-of-sight, and the key effect, which is infrared in nature, revealed through elementary harmonic oscillator networks. From there, it is natural to generalize
lattices to other graphs/networks. In this setting, the presence of spontaneous
symmetry breaking is controlled by fractional generalizations of resistance distance and the Kirchhoff index, and most broadly by the spectral dimension. Predictably, because of the richness of discrete
geometric structures in comparison with continuous
manifolds, a broader array of geometries emerge where spontaneous breaking of continuous
symmetries is blocked by large fluctuations.
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Soft Condensed Matter
Modeling Complex Multiphysics Systems with Discrete Element Method Enriched with the Kernel-Independent Fast Multipole Method
Igor A. Ostanin
The paper describes the coupling of the MercuryDPM discrete element method (DEM) code and the implementation of the kernel-independent fast multipole method (KIFMM). The combined simulation framework allows addressing the large class of multiscale problems, including both the mechanical interactions of particulates at the fine scale and the long-range interactions of various natures at the coarse scale. Among these are electrostatic interactions in powders, clays, and particulates,
magnetic interactions in
ferromagnetic granulates, and gravitational interactions in asteroid clouds. The formalism of rigid clumps is successfully combined with KIFMM, enabling addressing problems involving complex long-large interactions between non-spherical particles with arbitrary charge distributions. The capabilities of our technique are demonstrated in several application examples.
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Mesoscale and Nanoscale Physics
Modeling the dynamics of trapped electrons in quantum dots
R. Carmina Monreal
We analyze the effects of electron-electron and electron-
phonon interactions in the dynamics of a system of two or three electrons that can be trapped to a localized state and detrapped to ab extended band states of a
quantum dot using a simple model. In spite of its simplicity the time dependent problem has no analytical solution but a numerically exact one can be found at a relatively low computational cost. Within this model, we study the time
evolution of the electron occupancies of conduction and valence bands and the trap state, as well as the statistical factors influencing light emission of different energies. In most of the analyzed cases, the system dynamics has a very short transient determined by the hopping parameters, that can be of tens of femptoseconds,followed by a quasi-stationary regime in which the electron occupancies either oscillate periodically around their time-averaged values or remain nearly constant. We find signatures of strong electronic correlations in the electronic motion for negative values of the effective electron-electron Coulomb interaction that are not translated to the statistical factors for light emission. Our calculations show that light emission of different energies is always possible except in the especial cases in which the valence band is initially filled with two electrons. In these cases the valence band can lose and recover electrons periodically but
exciton emission is negligible at any time. We use this fact to attempt to give a possible explanation for the increase in the intensity of
exciton emission with the concomitant decrease in the intensity of the green emission lines upon continuous illumination with ultraviolet radiation, experimentally observed for ZnO nanoparticles suspended in an alcohol.
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Soft Condensed Matter · Cross-listed from physics.chem-ph
Deep learning of committor for ion dissociation and interpretable analysis of solvent effects using atom-centered symmetry functions
Kenji Okada, Kazushi Okada, Kei-ichi Okazaki et al. (+3 more)
The association and dissociation of ion pairs in water are fundamental to physical chemistry, yet their reaction coordinates are complex, involving not only interionic distance but also solvent-mediated hydration structures. These processes are often represented by free-energy landscapes constructed from collective variables (CVs), such as interionic distance and water bridging structures; however, it remains uncertain whether such representations reliably capture the transition pathways between the two associated and dissociated states. In this study, we employ deep learning to identify reaction coordinates for NaCl ion pair association and dissociation in water, using the committor as a quantitative measure of progress along the transition pathway through the transition state. The solvent environment surrounding the ions is encoded through descriptors based on atom-centered
symmetry functions (ACSFs), which serve as input variables for the neural network. In addition, an explainable artificial intelligence technique is applied to identify ACSFs that contribute to the reaction coordinate. A comparative analysis of their correlation with CVs representing water bridging structures, such as interionic water density and the number of water molecules coordinating both ions, further provides a molecular-level interpretation of the ion association-dissociation mechanism in water.
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All authors Kenji Okada, Kazushi Okada, Kei-ichi Okazaki, Toshifumi Mori, Kang Kim, Nobuyuki Matubayasi
Other Condensed Matter
A First Look at Hydrogen Generation in an Ultramafic Rock with Micro-CT and SEM-BEX
Hannah P. Menke, Zaid Z. Jangda, CJ Jones et al. (+3 more)
We present a 4D (time-lapse) micro-CT experiment that visualizes gas emergence and growth during water-rock reaction in an ultramafic granular pack at 100$^\circ$C. Repeated scans resolve the onset of gas exsolution after an initial delay, followed by rapid bubble growth, coalescence, and evolving gas connectivity. Image-derived metrics quantify changes in bulk gas saturation and gas clustering through time. Hydrogen was detected independently in the pump effluent and by an indicator strip in the confining sleeve. A companion reactor experiment using the same parent rock at 100$^\circ$C yielded an estimated net production of 0.65 mmol H$_2$ over approximately three weeks, accounting for dissolved hydrogen and gas removed during sampling. Complementary SEM and multi-element backscattered electron and X-ray (BEX) imaging of pre- and post-reaction grains indicates localized alteration textures consistent with reaction-driven H$_2$ production. These observations constrain pore-scale gas accumulation and multiphase transport relevant to natural hydrogen accumulations.
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All authors Hannah P. Menke, Zaid Z. Jangda, CJ Jones, Max Webb, Jim Buckman, Amy Gough
Materials Science
Twin Domains in 111 oriented {CdO/MgO} superlattices: homoepitaxy versus heteroepitaxy
Ewa Przeździecka, Aleksandra Wierzbicka, Abinash Adhikari et al. (+1 more)
The structural properties of (111)-oriented {CdO/MgO} superlattice structures grown on c-sapphire and cubic MgO substrates have been studied by high resolution X-ray diffraction. The growth was performed in a
plasma-assisted molecular beam epitaxy system. Although both superlattices are (111)-oriented and the {CdO/MgO} structure has 3m
symmetry. It was shown that the superlattice on c-sapphire consists of misoriented domains, whereas no such domains were observed on (111) MgO. The twin domains are rotated by 180{\deg} with respect to each other and by 30{\deg} with respect to the sapphire substrate. We show that the crucial phenomena based on the formation of rotation domains and their number in heteroepitaxy depend fundamentally on the relationship between substrate and epilayer
symmetries.
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All authors Ewa Przeździecka, Aleksandra Wierzbicka, Abinash Adhikari, Marta A. Chabowska
Materials Science
Symmetry-driven giant magneto-optical Kerr effects in altermagnet hematite
Jiaxin Luo, Xiaodong Zhou, Jinxuan Liang et al. (+7 more)
Altermagnets have attracted tremendous interest for revealing intriguing physics and promising spintronics applications. In contrast to conventional antiferromagnets, altermagnets break both PT and Tt
symmetries, and simultaneously exhibit
spin-split band structures with a vanishing net magnetization. To quantify insulating altermagnets without conduction electron, we propose to use magneto-optical Kerr effect (MOKE) to identify the altermagnetic fingerprints. In particular, we demonstrate not only the
giant MOKE responses, but also their connection with the orientations of Neel vectors at room temperature in altermagnet hematite alpha-Fe_2O_3. Specifically, under the Neel vector along the [1-100] axis, we find a
giant polar Kerr rotation angle 93.4 mdeg in the (11-20) plane, which is allowed by the
magnetic space group C2'/c'. Under the Neel vector along the [11-20] axis, we find a longitudinal Kerr angle 9.6 mdeg in the (0001) plane, which is allowed by the
magnetic space group C2/c. Further, we show that such pronounced MOKE effects directly enable an optical imaging of altermagnetic domains, together with their reversible domain wall (DW) motion. Our studies not only suggest MOKE can be used to identify altermagnet candidates, but also signify the feasibility of exploring altermagnetic optical and DW spintronics, which could largely expand the current research paradigm of altermagnetism.
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All authors Jiaxin Luo, Xiaodong Zhou, Jinxuan Liang, Ledong Wang, Qiuyun Zhou, Yong Jiang, Wenhong Wang, Yugui Yao, Luyi Yang, Wanjun Jiang
Soft Condensed Matter
Exact Screening-Ranged Expansions for Many-Body Electrostatics
Sergii V. Siryk and Walter Rocchia
We present an exact many-body framework for electrostatic interactions among $N$ arbitrarily charged spheres in an electrolyte, modeled by the linearized Poisson–Boltzmann equation. Building on a spectral analysis of nonstandard Neumann–Poincaré-type operators introduced in a companion mathematical work arXiv:2512.08684, we construct convergent screening-ranged series for the potential, interaction energy, and forces, where each term is associated with a well-defined Debye–Hückel screening order and can be obtained evaluating an analytical expression rather than numerically solving an infinitely dimensional linear system. This formulation unifies and extends classical and recent approaches, providing a rigorous basis for electrostatic interactions among heterogeneously charged particles (including Janus colloids) and yielding many-body generalizations of analytical explicit-form results previously available only for two-body systems. The framework captures and clarifies complex effects such as asymmetric dielectric screening, opposite-charge repulsion, and like-charge attraction, which remain largely analytically elusive in existing treatments. Beyond its fundamental significance, the method leads to numerically efficient schemes, offering a versatile tool for modeling colloids and soft/biological matter in electrolytic solution.
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Materials Science
Electrical Characterization of High-k (k>115) Crystalline SrTiO3 (STO) thin film integration with GaN with Nanomembrane Transfer Process
Md Tahmidul Alam, Kyoungjun Lee, Guangying Wang et al. (+2 more)
High-k (115), crystalline SrTiO3 (STO) thin film was transferred on GaN for potential applications in power devices (transistor and diodes) by nanomembrane transfer method and the detailed electrical properties such as leakage current, CV profiles, dielectric constant, frequency dispersion was reported from fabricated MOSCAP structures. The leakage current was negligible (under noise-level of tool) up to 6 V and 11 V for 50 nm and 200 nm STO membrane respectively A high-quality dielectric was indicated by the CV profile, which showed almost negligible frequency dispersion in the frequency range of 10 kHz to 500 kHz. The dielectric constant was 50 to 82 with the 50 nm thick STO membrane and 115 to 186 in the 200 nm thick STO membrane. Thermal annealing of the membrane in ambient conditions at 250 degrees for 2 hours led to a slight improvement in the dielectric constant (8 to 20 percent), albeit at the expense of degraded leakage current performance, as indicated by a reduction of 1 V to 3 V in the "no leakage region" of the IV curves after annealing. The possible physical mechanisms responsible for these changes were also analyzed and discussed.
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All authors Md Tahmidul Alam, Kyoungjun Lee, Guangying Wang, Chang-beom Eom, Chirag Gupta
Materials Science · Cross-listed from cs.DL
Optimizing Data Extraction from Materials Science Literature: A Study of Tools Using Large Language Models
Wenkai Ning, Musen Li, Jeffrey R. Reimers et al. (+1 more)
Large
Language Models (LLMs) are increasingly utilized for large-scale extraction and organization of unstructured data owing to their exceptional Natural
Language Processing (NLP) capabilities. Empowering materials design, vast amounts of data from experiments and simulations are scattered across numerous scientific publications, but high-quality experimental databases are scarce. This study considers the effectiveness and practicality of five representative AI tools (ChemDataExtractor, BERT-PSIE, ChatExtract, LangChain, and Kimi) to extract bandgaps from 200 randomly selected Materials Science publications in two presentations (arXiv and publisher versions), comparing the results to those obtained by human processing. Although the integrity of data extraction has not met expectations, encouraging results have been achieved in terms of precision and the ability to eliminate irrelevant papers from human consideration. Our analysis highlights both the strengths and limitations of these tools, offering insights into improving future data extraction techniques for enhanced scientific discovery and innovation. In conjunction with recent research, we provide guidance on feasible improvements for future data extraction methodologies, helping to bridge the gap between unstructured scientific data and structured, actionable databases.
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All authors Wenkai Ning, Musen Li, Jeffrey R. Reimers, Rika Kobayashi
Disordered Systems and Neural Networks · Cross-listed from q-bio.NC
Meta-learning three-factor plasticity rules for structured credit assignment with sparse feedback
Dimitra Maoutsa
Biological neural networks learn complex behaviors from sparse, delayed feedback using local synaptic plasticity, yet the mechanisms enabling structured credit assignment remain elusive. In contrast, artificial recurrent networks solving similar tasks typically rely on biologically implausible global learning rules or hand-crafted local updates. The space of local plasticity rules capable of supporting learning from delayed reinforcement remains largely unexplored. Here, we present a meta-learning framework that discovers local learning rules for structured credit assignment in recurrent networks trained with sparse feedback. Our approach interleaves local neo-Hebbian-like updates during task execution with an outer loop that optimizes plasticity parameters via tangent-propagation through learning. The resulting three-factor learning rules enable long-timescale credit assignment using only local information and delayed rewards, offering new insights into biologically grounded mechanisms for learning in recurrent
circuits.
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