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Physics Condensed Matter

cond-mat Watch Condensed Matter

Sunday 7 December

Soft Condensed Matter

Residual Force Determines Surface Tension in Active Systems

Bal Krishan

The mechanical tension at the interface of motility-induced phase separating active Brownian particles (ABPs) remains an open question. Here, we determine the surface tension by analyzing the spatial distribution of forces at the molecular level in a slab-confined system of ABPs exhibiting high and low density regions separated by a one-dimensional active interface. Unlike previous approaches that evaluate active and interaction stresses independently - often producing near-zero or negative surface tension - we show that on average, interaction forces act antagonistically to active propulsion, reducing the net force experienced by particles. By evaluating the work required to bring a particle to the interface using this total-force framework, we find a positive and physically consistent surface tension. These results reframe the mechanical interpretation of local stresses and provide a generalizable method for connecting microscopic force distributions to emergent interfacial properties in nonequilibrium systems.
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Strongly Correlated Electrons

Exploring electron spin dynamics in spin chains using defects as a quantum probe

L. Soriano, A. Manoj-Kumar, G. Gerbaud et al. (+7 more)

We investigate the quantum dynamics of the electron spin resonance of topological defects (edge state) in dimerized chains. These objects are discontinuities of the spin chain protected by the properties of the global system leading to a quantum many-body multiplet protected from the environment decoherence. Despite recent achievements in the realization of isolated and finite spin chains, the potential implementation in quantum devices needs the knowledge of the relaxation and decoherence sources. Our study reveals that electron spin lattice relaxation is governed at lowest temperatures by phonon-bottlenecked process and at high temperature by the chain dimerization gap. We show that the inter edge-state effective dipolar field is reduced by the intrachain exchange coupling leading to a longer coherence time than isolated ions at equivalent concentration. Ultimately, we demonstrate that the homogeneous broadening is governed by the intra-chain dipolar field, and we establish design principles for optimizing coherence in future materials.
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All authors L. Soriano, A. Manoj-Kumar, G. Gerbaud, A. Savoyant, R. Dassonneville, H. Vezin, O. Jeannin, M. Orio, M. Fourmigué, S. Bertaina

Strongly Correlated Electrons · Cross-listed from quant-ph

Witnessing Spin-Orbital Entanglement using Resonant Inelastic X-Ray Scattering

Zecheng Shen, Shuhan Ding, Zijun Zhao et al. (+2 more)

Entanglement plays a central role in quantum technologies, yet its characterization and control in materials remain challenging. Recent developments in spectrum-based entanglement witnesses have enabled new strategies for quantifying many-body entanglement in macroscopic materials. Here, we develop a protocol for detecting spin-orbital entanglement using experiment-accessible resonant inelastic x-ray scattering (RIXS). Central to our approach is the construction of a Hermitian generator from experimentally measurable spectra, which allows us to compute the quantum Fisher information (QFI) available in spin–orbital systems. The resulting QFI provides upper bounds for $k$-producible states and thus serves as a robust witness of spin-orbital entanglement. To account for realistic experimental limitations, we further extend our framework to include relaxed QFI bounds applicable to measurements lacking full polarization resolution.
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All authors Zecheng Shen, Shuhan Ding, Zijun Zhao, Francesco A. Evangelista, Yao Wang

Statistical Mechanics · Cross-listed from quant-ph

Interplay between Standard Quantum Detailed Balance and Thermodynamically Consistent Entropy Production

Xin-Hai Tong, Kohei Yoshimura, Tan Van Vu et al. (+1 more)

We demonstrate that, for a quantum Markovian semigroup on a finite-dimensional Hilbert space, if it satisfies the standard quantum detailed balance condition, its generator admits a special representation that yields a vanishing entropy production rate. Conversely, if the generator admits a special representation adhering to the condition of thermodynamic consistency and leading to a vanishing entropy production rate, then the corresponding quantum Markovian semigroup must satisfy the standard quantum detailed balance condition. In this context, we adopt the definition of entropy production rate that is motivated by the physics literature and standard for thermodynamically consistent Lindbladians.
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All authors Xin-Hai Tong, Kohei Yoshimura, Tan Van Vu, Naruo Ohga

Materials Science

Learning Thermoelectric Transport from Crystal Structures via Multiscale Graph Neural Network

Yuxuan Zeng, Wei Cao, Yijing Zuo et al. (+7 more)

Graph neural networks (GNNs) are designed to extract latent patterns from graph-structured data, making them particularly well suited for crystal representation learning. Here, we propose a GNN model tailored for estimating electronic transport coefficients in inorganic thermoelectric crystals. The model encodes crystal structures and physicochemical properties in a multiscale manner, encompassing global, atomic, bond, and angular levels. It achieves state-of-the-art performance on benchmark datasets with remarkable extrapolative capability. By combining the proposed GNN with ab initio calculations, we successfully identify compounds exhibiting outstanding electronic transport properties and further perform interpretability analyses from both global and atomic perspectives, tracing the origins of their distinct transport behaviors. Interestingly, the decision process of the model naturally reveals underlying physical patterns, offering new insights into computer-assisted materials design.
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All authors Yuxuan Zeng, Wei Cao, Yijing Zuo, Fang Lyu, Wenhao Xie, Tan Peng, Yue Hou, Ling Miao, Ziyu Wang, Jing Shi

Strongly Correlated Electrons

Spurious Strange Correlators in Symmetry-Protected Topological Phases

Wei-Liang Gao, Jie-Yu Zhang, Zheng-Xin Liu et al. (+1 more)

Strange correlator is a powerful tool widely used in detecting symmetry-protected topological (SPT) phases. However, the result of strange correlator crucially relies on the adoption of the reference state. In this work, we report that an ill-chosen reference state can induce spurious long-range strange correlators in trivial SPT phases, leading to false positives in SPT diagnosis. Focusing on 1D gapped bosonic/spin systems described by matrix product states (MPS), we trace the origin of these spurious signals in trivial SPT phases to the magnitude-degeneracy of the transfer matrix. We systematically classify three distinct mechanisms responsible for such degeneracy, each substantiated by concrete examples: (1) the presence of high-dimensional irreducible representations (abbreviated as irrep) in the eigenspace corresponding to the entanglment spectrum (entanglement space); (2) a phase mismatch in symmetry representations between the target and reference states; and (3) long-range order arising from symmetry breaking. Our findings clarify the importance of the choice of proper reference states, providing a guideline to avoid pitfalls and correctly identify SPT order using strange correlators.
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All authors Wei-Liang Gao, Jie-Yu Zhang, Zheng-Xin Liu, Peng Ye

Soft Condensed Matter

Surface energy-driven crumpling transition in a thin sheet under compression

Aashna Chawla and Deepak Kumar

In our common experience, crumpling a sheet requires external compressive force and leads to a random network of folds. However, thin sheets have been theoretically predicted to spontaneously transition from a flat to a crumpled state driven by thermal fluctuations, a phenomenon that has been elusive in experiments. We report the first observation of a similar crumpling transition driven instead by surface energy. Using a sensitive experimental protocol, when we gently compress a thin polymer sheet weakly adhered to a hydrogel substrate it transitions to a self-crumpling state at a well defined critical compression independent of system details. The transition is marked by the percolation of a fold network, and a power law increase in fold density. Most remarkably, the crumpled state shows a tunable order of folds establishing the phenomenon's potential as a simple and scalable technique to do origami with extremely thin sheets.
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Mesoscale and Nanoscale Physics

Full Electrical Switching of a Freestanding Ferrimagnetic Metal for Energy-Efficient Bipolar Neuromorphic Computing

Li Liu, Peixin Qin, Xiang Wang et al. (+11 more)

Flexible electronics and neuromorphic computing face key challenges in material integration and function retention. In particular, freestanding membranes suffer from slow sacrificial layer removal and interfacial strain, while neuromorphic hardware often relies on area-intensive dual-device schemes for bipolar synaptic weights. Here, we present a universal strategy based on water-soluble Sr4Al2O7 sacrificial layers, enabling the rapid release of freestanding ferrimagnetic metal membranes, which exhibit deterministic spin-orbit torque switching characteristics with well-preserved perpendicular magnetic anisotropy and are potential for next-generation ultrafast information technology. Extending this approach, we realize single-device ferrimagnetic synapses exhibiting intrinsic bipolar resistive switching. When implemented in a ResNet-18 architecture, these devices achieve 92% accuracy on CIFAR-10 - comparable to floating-point software models - while halving device counts relative to differential-pair implementations. These results establish a scalable platform linking flexible spintronics with compact, high-performance neuromorphic systems, offering foundational advances for next-generation electronics and brain-inspired hardware.
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All authors Li Liu, Peixin Qin, Xiang Wang, Xiaobo She, Shaoxuan Zhang, Xiaoning Wang, Hongyu Chen, Guojian Zhao, Zhiyuan Duan, Ziang Meng, Qinghua Zhang, Qiong Wu, Yu Liu, Zhiqi Liu

Materials Science

Freestanding Thin-Film Materials

Li Liu, Peixin Qin, Guojian Zhao et al. (+7 more)

Freestanding thin films, a class of low-dimensional materials capable of maintaining structural integrity without substrates, have emerged as a forefront research focus. Their unique advantages-circumventing substrate clamping, liberating intrinsic material properties, and enabling cross-platform heterogeneous integration-underpin this prominence. This review systematically summarizes core fabrication techniques, including physical delamination (e.g., laser lift-off, mechanical exfoliation) and chemical etching, alongside associated transfer strategies. It further explores the induced strain modulation mechanisms, extreme mechanical properties and interface decoupling effects enabled by these films. Representative case studies demonstrate breakthrough applications in flexible/ultrathin electronics, ultrahigh-sensitivity sensors and the exploration of novel quantum states. Critical challenges regarding scalable fabrication, precise interface control, and long-term stability are analyzed, concluding with prospects for emerging applications in bio-inspired intelligent devices, quantum precision sensing, and brain-inspired neural networks.
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All authors Li Liu, Peixin Qin, Guojian Zhao, Zhiyuan Duan, Jingyu Li, Sixu Jiang, Xiaoyang Tan, Xiaoning Wang, Ziang Meng, Zhiqi Liu

Soft Condensed Matter

Compression-driven jamming in porous cohesive aggregates

Sota Arakawa

I investigate the compression-driven jamming behavior of two-dimensional porous aggregates composed of cohesive, frictionless disks. Three types of initial aggregates are prepared using different aggregation procedures, namely, reaction-limited aggregation (RLA), ballistic particle-cluster aggregation (BPCA), and diffusion-limited aggregation (DLA), to elucidate the influence of aggregate morphology. Using distinct-element-method simulations with a shrinking circular boundary, I numerically obtain the pressure as a function of the packing fraction $\phi$. For the densest RLA and the intermediate BPCA aggregates, a clear jamming transition is observed at a critical packing fraction $\phi_{\rm J}$, below which the pressure vanishes and above which a finite pressure emerges; the transition is less distinct for the most porous DLA aggregates. The jamming threshold depends on the initial structure and, when extrapolated to infinite system size, approaches $\phi_{\rm J} = 0.765 \pm 0.004$ for RLA, $0.727 \pm 0.004$ for BPCA, and $0.602 \pm 0.023$ for DLA, where the errors denote the standard error. Above $\phi_{\rm J}$, the pressure follows $P \approx A {( \phi - \phi_{\rm J} )}^{2}$, which implies that the bulk modulus $K$ of jammed aggregates is proportional to $\phi - \phi_{\rm J}$. Rigid-cluster analysis of jammed aggregates shows that the average coordination number within the largest rigid cluster increases linearly with $\phi - \phi_{\rm J}$. Taken together, these relations suggest that the elastic response of compressed porous aggregates is analogous to that of random spring networks.
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Saturday 6 December

Mesoscale and Nanoscale Physics

On fast charged particles scattering on zigzag nanotube

Viktoriia Omelchenko

A fast charged particle scattering on a single-wall carbon nanotube of zigzag type was considered. The differential cross sections of scattering on nanotubes of different spatial orientation with respect to the incident particles were obtained. The eikonal approximation of quantum electrodynamics and the continuous potential approximation were used.
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Materials Science

Doping induced magnetism and half-metallicity in nanoribbons of quartic dispersion materials

Emin Aliyev, Arash Mobaraki, Hâldun Sevinçli et al. (+1 more)

Two-dimensional (2D) quartic dispersion materials are known to develop magnetization upon doping. Here we conduct a systematic investigation of magnetization in hole-doped quartic dispersion materials (GaS, InSe, TiO$_{2}$), focusing on the effects of structural confinement from 2D monolayers to quasi-one-dimensional nanoribbons (NRs). Upon hole doping, these NRs develop itinerant magnetization across a broad range of carrier densities and display half-metallic behavior. The spin-polarization energies ($E_{sp}$) of these NRs enhance remarkably relative to their 2D counterparts, with maximum increase being in the case of TiO$_{2}$ from 31 to 103 meV/carrier. The $E_{sp}$ strongly depends on the degree of localization of the magnetic moments along the width of NRs, which is determined by edge passivation and ribbon width. Strong deformation of the topmost valence bands at higher dopings indicates deviation from the Stoner mechanism.
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All authors Emin Aliyev, Arash Mobaraki, Hâldun Sevinçli, Seymur Jahangirov

Strongly Correlated Electrons

Coincidence detection techniques for direct measurement of many-body correlations in strongly correlated electron systems

Yuehua Su, Guoya Zhang, Chao Zhang et al. (+1 more)

Research on strongly correlated electron systems faces a fundamental challenge due to the complex nature of intrinsic many-body correlations. A key strategy to address this challenge lies in advancing experimental methods that can directly probe and elucidate the underlying many-body correlations. In this perspective article, we discuss the theoretically proposed coincidence detection techniques, which are designed to directly measure two-body correlations in various particle-particle and particle-hole channels, with momentum, energy, and/or spatial resolution. We also explore the prospects of these coincidence detection techniques for future theoretical and experimental developments. The successful implementation and refinement of these coincidence detection techniques promise to deliver powerful new approaches for unraveling long-standing puzzles in strongly correlated electron systems, such as the enigmatic mechanism of unconventional superconductivity and the long-sought quantum spin liquids. Furthermore, these coincidence detection techniques will offer powerful new methods to investigate novel phenomena like itinerant magnetism and electronic nematicity in quantum materials.
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All authors Yuehua Su, Guoya Zhang, Chao Zhang, Dezhong Cao

Mesoscale and Nanoscale Physics

Localization, transport, flux induced extended modes and mobility edge in a self-similar corral substrate

Sayan Bhattacharya, Rhiddha Acharjee and Atanu Nandy

We address that a single-band tight-binding Hamiltonian defined on a self-similar corral substrate can give rise to a set of non-diffusive localized modes that follow the same hierarchical distribution. As the lattice, the spatial extent of quantum prison containing a cluster of atomic sites is dependent on the generation of fractal structure. Apart from the quantum imprisonment of the excitation, a magnetic flux threading each elementary plaquette is shown to destroy the boundedness and generate an absolutely continuous sub-band populated by resonant eigen functions. Flux induced engineering of quantum states is corroborated through the evaluation of inverse participation ratio and quantum transport. Moreover, the robustness of the extended states has been checked in presence of diagonal disorder and off-diagonal anisotropy. Flux modulated single-particle mobility edge is characterized through mutlifractal analysis. Quantum interference is the essential issue, reported here, that manipulates the kinematics of the excitation and this is manifested by the workout of persistent current.
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Materials Science

Chemical Vapor Deposition of Nitrides by Carbon-free Brominated Precursors

Stefano Leone, Teresa Duarte, Hanspeter Menner et al. (+6 more)

The epitaxial growth of group 13-nitride semiconductors (GaN, AlN, and AlGaN alloys) for the mass production and fabrication of high-frequency and high-power devices relies on metal-organic chemical vapor deposition (MOCVD) using metal-organic molecules, also called precursors. While this growth method ensures high productivity and low operation costs compared to other methods, its most significant disadvantage lies in the presence of carbon atoms in the precursors, which are unavoidably incorporated into the epitaxial layers and hamper the performance of most types of fabricated devices. Carbon-free precursors for the CVD process could enhance the performance of high-frequency and high-power nitride-based devices while maintaining growth capability in industrial equipment. In this work, we implement gallium- and aluminum-brominated precursors, which contain no carbon atoms, to grow GaN and AlN layers in an industrial CVD system. We compare the results of this alternative CVD process with the conventional method using trimethyl precursors through several characterization techniques, indicating a clear reduction in optically active carbon-related defects.
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All authors Stefano Leone, Teresa Duarte, Hanspeter Menner, Jannik Richter, Lutz Kirste, Sven Maegdefessel, Felix Hoffmann, Byeongchan So, Ruediger Quay

Soft Condensed Matter · Cross-listed from physics.flu-dyn

Concentration Matters: Enhancing Particle Settling in Narrow Tilted Channels

Dipankar Kundu, Florencio Balboa Usabiaga, Adolfo Vázquez-Quesada et al. (+1 more)

Particles are known to sediment faster in containers with tilted walls than in vertical ones, a phenomenon known as the Boycott effect. In this work, we investigate how the tilt angle influences sedimentation in narrow channels across different particle volume fractions. Using particle-resolved computational fluid dynamics simulations, we reveal that there exists a concentration-dependent optimal tilt angle that maximizes sedimentation rates. Furthermore, at large tilt angles, the flow profiles across the channel deviate from the classical parabolic shape. We show that these non-parabolic profiles can be accurately captured by a one-dimensional Brinkman model, providing a predictive framework for understanding and tuning sedimentation in tilted geometries. Our findings demonstrate the potential to control and optimize particle settling by adjusting the channel tilt according to particle concentration, opening new possibilities for design in industrial and laboratory processes.
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All authors Dipankar Kundu, Florencio Balboa Usabiaga, Adolfo Vázquez-Quesada, Marco Ellero

Statistical Mechanics · Cross-listed from cs.LG

Hierarchical geometric deep learning enables scalable analysis of molecular dynamics

Zihan Pengmei, Spencer C. Guo, Chatipat Lorpaiboon et al. (+1 more)

Molecular dynamics simulations can generate atomically detailed trajectories of complex systems, but analyzing these dynamics can be challenging when systems lack well-established quantitative descriptors (features). Graph neural networks (GNNs) in which messages are passed between nodes that represent atoms that are spatial neighbors promise to obviate manual feature engineering, but the use of GNNs with biomolecular systems of more than a few hundred residues has been limited in the context of analyzing dynamics by both difficulties in capturing the details of long-range interactions with message passing and the memory and runtime requirements associated with large graphs. Here, we show how local information can be aggregated to reduce memory and runtime requirements without sacrificing atomic detail. We demonstrate that this approach opens the door to analyzing simulations of protein-nucleic acid complexes with thousands of residues on single GPUs within minutes. For systems with hundreds of residues, for which there are sufficient data to make quantitative comparisons, we show that the approach improves performance and interpretability.
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All authors Zihan Pengmei, Spencer C. Guo, Chatipat Lorpaiboon, Aaron R. Dinner

Disordered Systems and Neural Networks

Statistical physics for artificial neural networks

Zongrui Pei

The 2024 Nobel Prize in Physics was awarded for pioneering contributions at the intersection of artificial neural networks (ANNs) and spin-glass physics, underscoring the profound connections between these fields. The topological similarities between ANNs and Ising-type models, such as the Sherrington-Kirkpatrick model, reveal shared structures that bridge statistical physics and machine learning. In this perspective, we explore how concepts and methods from statistical physics, particularly those related to glassy and disordered systems like spin glasses, are applied to the study and development of ANNs. We discuss the key differences, common features, and deep interconnections between spin glasses and neural networks while highlighting future directions for this interdisciplinary research. Special attention is given to the synergy between spin-glass studies and neural network advancements and the challenges that remain in statistical physics for ANNs. Finally, we examine the transformative role that quantum computing could play in addressing these challenges and propelling this research frontier forward.
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Materials Science

Interplay of Ferromagnetic and Antiferromagnetic Interactions in Epitaxial Co$_3$ZnN

Sita Dugu, Sharad Mahatara, Corlyn E Regier et al. (+4 more)

Antiperovskite nitrides with the general formula M$_3$N have attracted significant attention due to their tunable electronic and magnetic properties. Among them are many cobalt-based compounds predicted to exhibit high thermodynamic stability and intriguing magnetic behavior. Here, we report the synthesis and magnetic characterization of epitaxial Co$_3$ZnN thin films grown by radio frequency sputtering on SrTiO$_3$ (STO) and MgO substrates. X-ray diffraction confirms phase-pure (00l)-oriented films with cube-on-cube epitaxy on STO, with a c-lattice parameter of 3.752 angstroms. Magnetic measurements reveal clear hysteresis at 2 K with a coercive field of ~ 0.12 T and a small net moment of 0.11 ${\mu}_B$/f.u., suggesting either a canted antiferromagnetic (AFM) or ferrimagnetic (FiM) configuration. Temperature-dependent magnetization measurements show a transition near 25 K, with strong AFM interactions (Curie-Weiss $\Theta$ = -80.6 K) at high temperatures and short-range ferromagnetic correlations ($\Theta$ = +9.7 K) emerging near the transition. Complementary density functional theory (DFT) and Monte Carlo simulations indicate a ferromagnetic (FM) ground state, with the FM-AFM energy difference decreasing systematically with increasing supercell size, consistent with competition between FM and AFM/FiM interactions. These results highlight Co$_3$ZnN as a magnetically complex antiperovskite nitride with competing exchange interactions.
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All authors Sita Dugu, Sharad Mahatara, Corlyn E Regier, James R Neilson, Stephan Lany, Rebecca W. Smaha, Sage R Bauers

Statistical Mechanics

Convective Viscous Cahn-Hilliard/Allen-Cahn Equation with memory effects

P.O.Mchedlov-Petrosyan and L.N.Davydov

The combination of the well-known Cahn-Hilliard and Allen-Cahn equations is used to describe surface processes, such as simultaneous adsorption/desorption and surface diffusion. In the present paper we have considered the convective-viscous Cahn-Hilliard/Allen-Cahn equation complemented by memory effects. Exact solutions are obtained and the combined action of the applied field, dissipation and memory are discussed.
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Materials Science · Cross-listed from physics.optics

Giant optical anisotropy and visible-frequency epsilon-near-zero in hyperbolic van der Waals MoOCl2

Georgy Ermolaev, Adilet Toksumakov, Aleksandr Slavich et al. (+13 more)

The realization of extreme optical anisotropy is foundational to nanoscale light manipulation. Van der Waals (vdW) crystal MoOCl2 has emerged as a promising candidate for this quest, hosting hyperbolic plasmon polaritons in the visible and near-infrared wavelengths. However, the fundamental anisotropic dielectric tensor governing this behavior has remained elusive. Here, we resolve this problem by providing the first experimental determination of the full dielectric tensor of hyperbolic vdW MoOCl2. Via spectroscopic ellipsometry, Mueller matrix, and reflectance measurements, we quantify the material's optical duality: a metallic optical response ({\epsilon}_1 < 0) along the crystallographic a-axis and a dielectric response ({\epsilon}_1 > 0) along the orthogonal directions. This dichotomy drives an epsilon-near-zero (ENZ) condition at \approx 512 nm and results in giant in-plane birefringence of \delta n \approx 2.2 for MoOCl2. As a result, our work provides the critical missing experimental parameters for MoOCl2, establishing it as a benchmark hyperbolic and ENZ material.
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All authors Georgy Ermolaev, Adilet Toksumakov, Aleksandr Slavich, Anton Minnekhanov, Gleb Tselikov, Arslan Mazitov, Ivan Kruglov, Gleb Tikhonowski, Mikhail Mironov, Ilya Radko, Dmitriy Grudinin, Andrey Vyshnevyy, Zdeněk Sofer, Aleksey Arsenin, Kostya S. Novoselov, Valentyn Volkov

Mesoscale and Nanoscale Physics

Topological Defect Mediated Helical Phase Reorientation by Uniaxial Stress

Tae-Hoon Kim, Haijun Zhao, Brandt A. Jensen et al. (+2 more)

Strain engineering enables precise, energy-efficient control of nanoscale magnetism. However, unlike well-studied strain-dislocation interactions in mechanical deformation, the spatial evolution of strain-induced spin rearrangement remains poorly understood. Using in situ Lorentz transmission electron microscopy, we manipulate and observe helical domain reorientation under quantitatively applied uniaxial tensile stress. Our findings reveal striking similarity to plastic deformation in metals, where the critical stress for propagation vector (\emph{Q}) reorientation depends on its angle with the stress direction. Magnetic defects mediate reorientation via "break-and-reconnect" or "dislocation gliding-annihilation" processes. Simulations confirm that strain-induced anisotropic Dzyaloshinskii-Moriya interaction may play a key role. These insights advance strain-driven magnetism and offer a promising route for energy-efficient magnetic nanophase control in next-generation information technology.
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All authors Tae-Hoon Kim, Haijun Zhao, Brandt A. Jensen, Liqin Ke, Lin Zhou

Superconductivity

Robust Superconductivity and High Upper Critical Fields in Epitaxial cubic W2N Thin Films

Aditya Singh, Arnaud le Febvrier, Sanath Kumar Honnali et al. (+5 more)

Transition Metal Nitrides are a versatile class of materials, combining chemical robustness, high hardness, and superconducting behaviour with critical temperatures between 2 to 10 K. While several binary TMNs have been explored, superconductivity in stoichiometric W2N has remained largely unexplored. Here, we report on superconducting thin films of stoichiometric W2N, demonstrating a distinctly high upper critical field of 8.5 T, uncommon among binary TMNs. This robust superconducting response under high magnetic fields highlights the technological relevance of W2N for integrated quantum and cryogenic electronic platforms. Overall, these results position stoichiometric W2N as a promising addition to the TMN superconducting landscape, opening new avenues for functional materials design based on chemically stable and mechanically resilient nitrides.
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All authors Aditya Singh, Arnaud le Febvrier, Sanath Kumar Honnali, Abhisek Mishra, Grzegorz Greczynski, Subhankar Bedanta, Per Eklund, Ajay Soni

Mesoscale and Nanoscale Physics

Phase-Factor-Controlled Surface Spirals in the Magnetic Conical Phase: The Role of In-Plane Directionality

Haijun Zhao, Tae-Hoon Kim, Lin Zhou et al. (+1 more)

In chiral magnets, the magnetic textures surrounding domain walls exhibit a rich variety of structures, offering insights into fundamental physics and potential applications in spintronic devices. Conical spirals and related structures possess intrinsic in-plane directionalities governed by phase factors $\phi_0$, which are often obscured in long spirals due to cylindrical symmetry but become prominent in short spirals or thin films. Using micromagnetic simulations, we systematically studied magnetic textures at ferromagnetic-conical interfaces (FCI), including 1D and 2D FCIs with various shapes. Surface spirals (SS) emerge adjacent to these FCIs, closely linked to the cone's in-plane reorientation. In 1D FCIs, reorientation controls the presence, shape, and topological charge of the SS, with a discontinuity point observed where spirals with opposite charges form on opposite sides. In 2D FCIs, eyebrow-like SS are evident. The reorientation angle between top and bottom SS is controlled by the film thickness, similar to stacked spirals reported previously. We further demonstrate that SSs form at the facets of skyrmion clusters within the conical phase, as confirmed by both simulations and Lorentz transmission electron microscopy observations in Co$_8$Zn$_{10}$Mn$_2$ thin films. The experiments specifically reveal two distinct formation pathways: thermally activated co-growth and field-driven transformation from residual helices. These findings establish $\phi_0$ as a fundamental control parameter for magnetic states, enabling promising spintronic functionalities such as multi-state memory through SS polymorphism and energy-efficient neuromorphic computing via controlled topological transitions.
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All authors Haijun Zhao, Tae-Hoon Kim, Lin Zhou, Liqin Ke

Other Condensed Matter

Moiré pattern multiplicity driven by electronic effects in two-dimensional CrCl3/Au heterostructures

Eugenio Gambari, Hugo Le Du, Mathieu Lizée et al. (+7 more)

Moiré patterns are a central motif in van der Waals heterostructures arising from the superposition of two-dimensional (2D) incommensurate lattices. These patterns reveal a wealth of correlated effects, influencing electronic, magnetic, and structural phenomena. While diffraction techniques typically resolve multiple moiré wave-vectors corresponding to the incommensurate nature of the underlying lattices, Scanning Tunneling Microscopy (STM) often reveals only a dominant superperiod. In this work, we address this apparent discrepancy through an STM study of a twisted monolayer of CrCl3 on Au(111). We observe the coexistence of several moiré patterns at a fixed twist angle, whose relative intensity depends on the tunneling bias. Fourier analysis of STM data uncovers hidden higher-order moiré components not visible in STM topographic images, while spectroscopy maps reveal that the spectral weight of each pattern varies with electron energy. Our results establish that STM selectively probes on the same area distinct moiré modulations depending on electronic confinement, providing a unified framework that reconciles real space and reciprocal space observations of complex moiré superstructures.
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All authors Eugenio Gambari, Hugo Le Du, Mathieu Lizée, Arindam Mukherjee, Laurent Limot, Fabrice Scheurer, Marie D'angelo, François Debontridder, Tristan Cren, Marie Hervé

Mesoscale and Nanoscale Physics

Odd viscosity and anomalous Hall effect in two dimensional electron systems with smooth disorder

D.S. Zohrabyan and M.M. Glazov

A microscopic theory of odd viscosity in two-dimensional electron systems with smooth disorder and spin-orbit interaction is developed. It is shown that spin-orbit scattering in presence of spin polarization induced by magnetic field gives rise to an off-diagonal component of the viscosity tensor. Hydrodynamic equations for spin and electric currents are derived for electrons interacting with smooth disorder. The contribution of odd viscosity to the anomalous Hall effect is calculated.
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Statistical Mechanics

Thermodynamic description of world GDP distribution over countries

Klaus M. Frahm and Dima L. Shepelyansky

We apply the concept of Rayleigh-Jeans thermalization of classical fields for a description of the world Gross Domestic Product (GDP) distribution over countries. The thermalization appears due to a variety of interactions between countries with conservation of two integrals being total GDP and probability (norm). In such a case there is an emergence of Rayleigh-Jeans condensation at states with low GDP. This phenomenon has been studied theoretically and experimentally in multimode optical fibers and we argue that it is at the origin of emergence of poverty and oligarchic phases for GDP of countries. A similar phenomenon has been discussed recently in the framework of the Wealth Thermalization Hypothesis to explain the high inequality of wealth distribution in human society and companies at Stock Exchange markets. We show that the Rayleigh-Jeans thermalization well describes the GDP distribution during the last 50 years.
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Materials Science

Robust and tunable Floquet altermagnets in sliding A-type antiferromagnetic bilayers

Zhe Li, Lijuan Li, Mengxue Guan et al. (+1 more)

Arranging the stacking orders of A-type antiferromagnetic (A-AFM) bilayers offers a practical pathway to realizing two-dimensional altermagnets. Previous proposals, however, rely on stringent symmetry constraints, including layer groups and stacking registries. In this work, we demonstrate that circularly polarized light (CPL) irradiation breaks time-reversal symmetry, enabling altermagnetism without these restrictions. Our comprehensive symmetry analysis reveals that inversionsymmetric A-AFM bilayer building blocks can host altermagnetism that is robust against stacking slides and variations in illumination direction, with rich and continuously tunable symmetry representations. Using bilayer MnBi$_2$Te$_4$ as a case study, we show that out-of-plane CPL stabilizes distinct $f$-wave or $p$-wave altermagnetic states in forward stacking, while reverse stacking manifests an even-odd parity conversion of altermagnetism based upon specific sliding configurations. These revealments broaden the scope of altermagnet design in inversion-symmetric A-AFM bilayers and establish CPL as a versatile control knob for engineering altermagnetic symmetries.
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All authors Zhe Li, Lijuan Li, Mengxue Guan, Sheng Meng

Mesoscale and Nanoscale Physics

Interface controlled Berry phase and anisotropic spin-charge conversion in altermagnet-topological insulator bilayers

Juhi Singh and Narayan Mohanta

We propose an altermagnet-topological insulator bilayer as a platform to engineer Berry phase driven spin-charge responses using an interfacial buffer layer. Using a momentum-space lattice model and linear-response theory, we investigate a $d$-wave altermagnet coupled to a topological insulator and highlight the crucial role of spin-flip tunneling in shaping its electronic and transport properties. Interfacial hybridization strongly modifies the band structure, leading to anisotropic Rashba-Edelstein and Hall responses. The spin-flip component of the coupling induces an inverse $d$-wave spin texture in the altermagnetic bands, signaling the onset of an altermagnetic topological phase. This coupling also renders the Rashba-Edelstein effect strongly in-plane anisotropic, enhancing the transverse response relative to ferromagnetic or antiferromagnetic analogues. These results establish interfacial spin-flip tunneling as a practical control knob for direction-sensitive, stray-field-free spin-charge conversion in correlated topological heterostructures.
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Materials Science · Cross-listed from cs.AI

GENIUS: An Agentic AI Framework for Autonomous Design and Execution of Simulation Protocols

Mohammad Soleymanibrojeni, Roland Aydin, Diego Guedes-Sobrinho et al. (+4 more)

Predictive atomistic simulations have propelled materials discovery, yet routine setup and debugging still demand computer specialists. This know-how gap limits Integrated Computational Materials Engineering (ICME), where state-of-the-art codes exist but remain cumbersome for non-experts. We address this bottleneck with GENIUS, an AI-agentic workflow that fuses a smart Quantum ESPRESSO knowledge graph with a tiered hierarchy of large language models supervised by a finite-state error-recovery machine. Here we show that GENIUS translates free-form human-generated prompts into validated input files that run to completion on $\approx$80% of 295 diverse benchmarks, where 76% are autonomously repaired, with success decaying exponentially to a 7% baseline. Compared with LLM-only baselines, GENIUS halves inference costs and virtually eliminates hallucinations. The framework democratizes electronic-structure DFT simulations by intelligently automating protocol generation, validation, and repair, opening large-scale screening and accelerating ICME design loops across academia and industry worldwide.
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All authors Mohammad Soleymanibrojeni, Roland Aydin, Diego Guedes-Sobrinho, Alexandre C. Dias, Maurício J. Piotrowski, Wolfgang Wenzel, Celso Ricardo Caldeira Rêgo