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Physics Condensed Matter Materials Science

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Wednesday 25 February

Materials Science

Interplay between Relativistic Spin-Momentum Locking and Breaking of Inversion Symmetry: conditions for p-wave magnetism

Amar Fakhredine, Giuseppe Cuono, Jan Skolimowski et al. (+2 more)

We investigate the interplay between relativistic spin-momentum locking arising from altermagnetism and various forms of inversion symmetry breaking. Depending on the symmetry breaking, this can give rise to Rashba-type spin-orbit coupling (SOC), Weyl-type SOC, or the coexistence of two distinct spin-momentum lockings. We focus on the altermagnetic Ca2RuO4 as a testbed material. Our results reproduce the experimentally observed ground state, which is an A-centered magnetic order with the Neel vector along the b-axis, hosting spin cantings along the a- and c-axes but without weak ferromagnetism. Ca2RuO4 exhibits relativistic spin-momentum locking, with different even-parity wave orders for the three spin components. We interpret the experimental results on doped samples as evidence for a transition from a pure altermagnetic phase to a weak ferromagnetic phase. Under ferroelectric- and antiferroelectric-like distortions, there are no qualitative changes in the non-relativistic spin-momentum locking and in the weak ferromagnetism. However, we observe the rise of the Rashba or Weyl-type SOC. Using numerical and analytical models, we investigate which nodal planes persist when inversion symmetry is broken in the relativistic case. The spin-momentum locking of the other components adopt a p-wave character in the case of Rashba; in contrast, Weyl-type SOC disrupts all nodal planes, leaving only nodal lines. Finally, to simulate a stripe phase with structural distortions along the z-axis, we studied a modulated electric field inducing atomic displacements within one Ca2RuO4 layer. This produces a magnetic phase transition to an exotic altermagnetic state with two non-relativistic spin-momentum lockings hosting weak ferromagnetism. Our research presents a comprehensive analysis of various possible scenarios in altermagnets with breaking of inversion symmetries under relativistic effects
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All authors Amar Fakhredine, Giuseppe Cuono, Jan Skolimowski, Silvia Picozzi, Carmine Autieri

Materials Science · Cross-listed from cond-mat.mes-hall

Charge distribution across dislocation networks induced by a strained top layer in hexagonal boron nitride substrates

Isaac Soltero, James G. McHugh and Vladimir I. Fal'ko

Hexagonal boron nitride (hBN) flakes are key building blocks for encapsulating two-dimensional (2D) materials, providing atomically flat surfaces and an excellent dielectric environment for high-mobility field-effect transistors and tunnelling devices. However, strain induced during mechanical exfoliation and assembly of van der Waals heterostructures may lead to plastic deformations of the hBN surface, injecting dislocation lines between the topmost layer and the underlying film. Since a monolayer of hBN is non-centrosymmetric and exhibits a piezoelectric response to deformation, individual dislocations and, in particular their networks, can generate electrostatic potential modulations in the encapsulated 2D material. Here, we examine scenarios in which the top hBN layer is uniaxially strained and/or twisted, and show how lattice reconstruction into dislocation networks leads to the formation of piezoelectric charge hotspots that effectively behave as charged defects.
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Materials Science

ML-guided screening of chalcogenide perovskites as solar energy materials

Diego A. Garzón, Lauri Himanen, Luisa Andrade et al. (+2 more)

Chalcogenide perovskites have emerged as promising absorber materials for next-generation photovoltaic devices, yet their experimental realization remains limited by competing phases, structural polymorphism, and synthetic challenges. Here, we present a fully data-driven and experimentally grounded screening and ranking framework to assess the stability and experimental feasibility of chalcogenide perovskites, integrating interpretable analytical descriptors, machine-learning models, and sustainability metrics. Using a curated experimental dataset of halide and chalcogenide compounds, we derive a new tolerance factor via the SISSO (sure independence screening and sparsifying operator) algorithm that more accurately distinguishes perovskite-forming compositions than established tolerance-factor-based screening criteria. This descriptor is combined with generative crystal structure prediction, composition-based bandgap estimation, and machine-learning-based feasibility assessment to systematically explore a wide chemical space of hypothetical chalcogenide perovskites. The resulting candidates are further evaluated using sustainability indicators, enabling multi-objective ranking tailored to both single-junction and tandem photovoltaic architectures. Beyond identifying several promising and previously unexplored chalcogenide perovskites, this work demonstrates a transferable screening strategy for chemically constrained materials spaces that balances optoelectronic performance, experimental viability, and long-term sustainability.
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All authors Diego A. Garzón, Lauri Himanen, Luisa Andrade, Sascha Sadewasser, José A. Márquez

Materials Science

Harnessing magnetic anisotropy for nonlinear magnetization precession and spin waves

P. I. Gerevenkov, L. A. Shelukhin, Ia. A. Filatov et al. (+2 more)

The nonlinearity of magnetization precession and spin waves is a cornerstone of contemporary magnonics. We investigate nonlinear magnetization dynamics in a thin epitaxial iron film driven by femtosecond laser pulses in regimes of homogeneous precession and propagating magnetostatic spin wave packets. The magnetization precession anharmonicity, the generation of higher-order harmonics, and the dynamical rectification are experimentally demonstrated. The numerical solution of the non-linearized Landau-Lifshitz-Gilbert equation reveals that these effects stem from the asymmetry in the energy potential and are essentially thresholdless. This asymmetry is readily achievable when an external magnetic field with a strength comparable to the magnetic anisotropy field is applied close to the hard axis. This work establishes a connection between the geometry of the energy profile and nonlinear responses, paving the way for designing magnonic devices with controlled harmonic generation and nonlinear spin wave interaction.
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All authors P. I. Gerevenkov, L. A. Shelukhin, Ia. A. Filatov, P. A. Dvortsova, A. M. Kalashnikova

Materials Science

The Predictive Power of Chemical Bonding Analysis in Materials: a Perspective on Optoelectronic Properties

Gabriele Saleh and Liberato Manna

Chemical bonding governs how atoms interact to form compounds, thereby determining their physicochemical properties. Despite being an elusive concept, chemical bonding has led to the development of models and tools to explain and predict the behavior of chemical species. This perspective addresses the adoption of chemical bonding analysis to the study of optoelectronic materials, emphasizing the im-portance of its predictive aspect. After reviewing the evolution of chemical bonding models from the first Lewis formulation to the present day, the perspective discusses material classes and chemical bonding phenomena most relevant for light harvesting and emission. We delve into metal halide perovskites and structurally related materials, given their central role in optoelectronic research. Various aspects of chemical bonding in these materials are surveyed, from the structure-property relationship to the rationalization of their electronic properties through molecular orbital diagrams. Two chemical bonding features are particularly important for optoelectronic materials: the ns2 lone pairs of the cations typically found in these materials (e.g. Pb, Sb, Bi) and the antibonding nature of valence and/or conduction bands. We discuss in depth the models to predict the implications of these two phenomena on optoelectronic properties. We also explore chalcohal-ides, a class of materials whose optoelectronic properties are recently emerging. From the chemical bonding perspective, these materials display intriguing phenomena due to the interplay of various types of chemical bonds. Finally, we discuss our vision on the role of chemical bonding analysis in the future of materials science, including synergies and antitheses with machine learning.
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Materials Science · Cross-listed from physics.med-ph

Solderable Microcontroller-Integrated E-Textiles using UV-Tape-Assisted Laser Patterning Technique

Naoto Tomita, Suguru Sato, Toshihiro Takeshita et al. (+5 more)

In this study, we developed a UV-tape-assisted laser patterning (UT-Laser) technique that enables the simple transfer-based formation of wiring with line widths below 200 $\mu$m onto textile substrates. With the rapid advancement of wearable devices capable of acquiring various types of physiological and environmental information, research on electronic textiles (e-textiles)-in which electronic components are integrated into fabrics and clothing-has progressed considerably. However, integrating high-performance, rigid electronic components onto textiles remains challenging: the diameter of textile fibers limits the formation of fine wiring, making reliable mounting of such components difficult. To address these challenges, we devised the UT-Laser technique, in which thin foil or film materials are laser vector-cut on UV tape, and the adhesive strength is controlled through UV exposure. The unnecessary portions are selectively and collectively peeled away to form fine wiring, which is subsequently transferred onto the textile substrate. This approach enables facile fabrication of fine wiring with line widths below 200 $\mu$m on textiles. Furthermore, by forming fine wiring from a flexible copper clad laminate and transferring it onto heat-resistant glass cloth, electronic components can be soldered directly, allowing the fabrication of e-textile devices capable of withstanding more than 10,000 bending cycles. The prototype e-textile device fabricated using the proposed method integrates a microcontroller, USB connector, battery holder, flash memory, inertial measurement unit, and environmental sensors, and successfully acquires data related to stair climbing, respiration, and changes in body temperature during sleep.
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All authors Naoto Tomita, Suguru Sato, Toshihiro Takeshita, Aki Furusawa, Jarred Fastier-Wooller, Shun Muramatsu, Toshihiro Itoh, Michitaka Yamamoto

Materials Science

Monitoring Gallium-Induced Damage in Aluminum Alloys Using Nonlinear Resonant Ultrasound Spectroscopy

Jan Kober, Radovan Zeman, Josef Krofta et al. (+2 more)

Nonlinear Resonant Ultrasound Spectroscopy is a nonlinear ultrasonic technique which allows monitoring small variations in the microstructure of a medium and thus allows materials characterization and monitoring of damage evolution. Application of the technique to monitor Liquid Metal Embrittlement induced by gallium penetration in aluminum is presented here. To define indicators of material degradation, data treatment using the Singular Value Decomposition approach is introduced and discussed. Experimental results show that nonlinear properties are correlated with the state of the liquid metal in the solid matrix, allowing to identify different phases in the process of gallium diffusion along grain boundaries and within the bulk of individual grains. Furthermore, the evolution of gallium damage allows to study correlations between nonlinear, fast and slow dynamic properties.
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All authors Jan Kober, Radovan Zeman, Josef Krofta, Antonio S. Gliozzi, Marco Scalerandi

Materials Science · Cross-listed from cond-mat.str-el

Magnetic anisotropic pinning and symmetric breaking induced by interfacial coupling in topological-like ruthenate superlattices

Zhongyuan Jiang, Zhiwei Zhang, Kesen Zhao et al. (+9 more)

Interfacial engineering enables various emergent effects such as spin reorientations and transport anisotropy. Noncollinear spin textures are essential for realizing many emergent quantum transport phenomena. However, driving such spin structures requires precise control of the interfacial magnetic coupling in complex oxide heterostructures. Here, by utilizing competing exchange interactions at the interface between ferromagnetic metal SrRuO3 and ferromagnetic insulator LaCoO3, we discovered a noncollinear spin configuration in SrRuO3 sublayers. Magnetic stripes were induced by out-of-plane rather than in-plane magnetic fields, indicating strong anisotropy pinning in our superlattices. The observed magneto-transport anisotropy is well explained by our proposed spin configurations, accounting for contributions from both bulk and interface of the SrRuO3 layers. More interestingly, magnetic skymionic textures were absent even at high magnetic fields. The interfacial exchange interaction overwhelms the Dzyaloshinskii-Moriya interaction (DMI) that stabilizes skyrmions, featuring a higher exchange coupling energy than that for the topological spin textures. Our work highlights the potential of interfacial engineering in tuning the spintronic properties by designing proper interfacial interactions.
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All authors Zhongyuan Jiang, Zhiwei Zhang, Kesen Zhao, Wenjie Meng, Yuanyuan Zhao, Yubin Hou, Zhangzhang Cui, Jian Zhang, Zheling Shan, Haoliang Huang, Qingyou Lu, Yalin Lu

Materials Science

Computational Frameworks for Patterned Two-Dimensional Magnetism

Soham Chandra and Soumyajit Sarkar

Patterned two-dimensional (2D) magnetic nanostructures constitute geometry-engineered spin systems in which exchange, anisotropy, dipolar coupling, and finite-size effects operate on comparable energy scales. Spatial modulation of continuous magnetic films produces confinement-driven critical behavior, compensation phenomena, metastable switching pathways, and topologically nontrivial textures such as vortices and skyrmions. Computational modeling plays a central role in resolving this complexity, enabling quantitative construction of thermodynamic phase diagrams and analysis of geometry-dependent stability regimes. This review synthesizes theoretical and numerical frameworks for patterned 2D magnetism, including classical spin models, stochastic spin dynamics, rare-event methods, and multiscale parameterization informed by first-principles calculations. Representative systems-nanodot and antidot arrays, artificial spin-ice lattices, exchange-modulated heterostructures, and patterned van der Waals magnets - illustrate how geometry functions as an effective thermodynamic control parameter. Emerging directions in nonequilibrium modeling, multiphysics coupling, and scalable data-centric workflows are discussed in the context of predictive phase mapping. Patterned 2D magnetism thus exemplifies geometry as an effective thermodynamic variable in materials engineering and computational statistical physics, with phase stability and controlled spin textures at the core of next-generation spintronic architectures.
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Materials Science

Reasoning-Driven Design of Single Atom Catalysts via a Multi-Agent Large Language Model Framework

Dong Hyeon Mok, Seoin Back, Victor Fung et al. (+1 more)

Large language models (LLMs) are becoming increasingly applied beyond natural language processing, demonstrating strong capabilities in complex scientific tasks that traditionally require human expertise. This progress has extended into materials discovery, where LLMs introduce a new paradigm by leveraging reasoning and in-context learning, capabilities absent from conventional machine learning approaches. Here, we present a Multi-Agent-based Electrocatalyst Search Through Reasoning and Optimization (MAESTRO) framework in which multiple LLMs with specialized roles collaboratively discover high-performance single atom catalysts for the oxygen reduction reaction. Within an autonomous design loop, agents iteratively reason, propose modifications, reflect on results and accumulate design history. Through in-context learning enabled by this iterative process, MAESTRO identified design principles not explicitly encoded in the LLMs' background knowledge and successfully discovered catalysts that break conventional scaling relations between reaction intermediates. These results highlight the potential of multi-agent LLM frameworks as a powerful strategy to generate chemical insight and discover promising catalysts.
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All authors Dong Hyeon Mok, Seoin Back, Victor Fung, Guoxiang Hu

Materials Science

Robust Electrocaloric Performance Enabled by Highly-Polar Frustrated Nanodomains in NaNbO3-Based Ferrodistortive Relaxor

Feng Li, Changshun Dai, He Qi et al. (+9 more)

Solid-state refrigeration technologies, represented by electrocaloric effect (ECE), are renowned for zero global-warming-potential and high cooling efficiency. Synergistically achieving high electrocaloric effect ({\Delta}T) and wide temperature span ({\Delta}Tspan) for EC materials takes a leapfrog toward practical cooling applications, typical for integrated circuits. Guided by phase-field simulation, Ba(Ti, Hf)O3 dubbed as a polar wrench, establishes polar frustration by setting up local stress field and manipulating octahedral oxygen tilt (OOT) in NaNbO3-based relaxor. The resultant P4bm framework entails short-range and highly-polar ferrodistortive nanodomains, i.e., the abundant highly-polar nanodomains facilitate to increase entropy change and robust OOT enables to impede thermal perturbations. Consequently, a large {\Delta}T of 0.85 K and 0.70 K with an ultrawide {\Delta}Tspan of 118 K and 130 K is obtained, contributing to an ultrahigh figure of merit of > 90 K2 in NaNbO3-Ba(Ti, Hf)O3, significantly outperforms its counterparts. The local structure responsible for robust EC performances are decrypted through 2D information from atomic-resolution scanning transmission electron microscope, 3D big-box model constructed from neutron total scattering and DFT calculations. These findings highlight that polar frustration strategy in ferrodistortive relaxor enables to pioneer emergent EC performances, and also unearth potential entropy-change-based ferroelectric and ferromagnetic materials beyond.
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All authors Feng Li, Changshun Dai, He Qi, Jiecheng Liu, Xiaoming Shi, Heng Zhou, Qiong Yang, Mingsheng Long, Lei Shan, Chunchang Wang, Jianli Wang, Zhenxiang Cheng

Materials Science

Oxygen permeability and stability in the entropy-stabilized Co-based Perovskite oxygen permeable membranes

Zaichen Xiang, Rui Chen, Shuangyue Wang et al. (+5 more)

Oxygen transport membranes (OTMs), enabling catalytic reaction and gas separation, support crucial chemical engineering processes and decarbonization technologies, but their applications are hindered by limited oxygen permeation fluxes and inadequate long-term stability during operation. Here, a series of high-entropy perovskite OTMs based on La0.5Sr0.5CoO3 were designed and synthesized by the simple sol-gel method. The impact of varying doping ratios on the structure, surface morphology, oxygen permeability, and stability of these high-entropy OTMs was thoroughly examined. At 950 {\deg}C, the optimal composition, La0.25Sr0.25Gd0.2Nd0.2Pr0.1CoO3, achieved oxygen permeation fluxes of 1.62 mL min-1 cm-2 under air/He gradient and 1.46 mL min-1 cm-2 under air/CO2, respectively. Remarkably, all high-entropy OTMs demonstrated stable operation for over 100 h in a pure CO2 environment without a significant decline in performance. This finding paves a new way to enhance the structural and oxygen permeation stability of OTMs, and further promotes the application of OTMs in oxy-fuel combustion technologies aimed at improving CO2 capture and storage efficiency.
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All authors Zaichen Xiang, Rui Chen, Shuangyue Wang, Jingjun Qin, Wanyi Zhang, Yucheng Li, Lingyong Zeng, Huixia Luo

Materials Science · Cross-listed from cond-mat.mes-hall

Intertwined bulk photocarrier and interfacial barrier dynamics in van der Waals point-contact Schottky junctions

Munenori Yokota, Hiroyuki Mogi, Yutaka Mera et al. (+6 more)

Schottky junctions based on transition-metal dichalcogenides underpin next-generation optoelectronic devices, yet the nanoscale carrier dynamics that ultimately govern their performance remain largely inaccessible. Here, we employ optical pump-probe time-resolved atomic force microscopy (OPP-TR-AFM) to investigate the spatiotemporal response of a WSe$_2$/PtIr van der Waals Schottky junction. Under backside illumination, photocarriers generated in bulk WSe$_2$ produce a local junction response through coupled bulk carrier transport and interfacial barrier modulation. We show that the time-resolved current is consistently explained by the competition between long-lived hole diffusion governed by the occupancy of bulk trap states and thermionic emission current modulated by the surface photovoltage. This mechanism is supported by transient absorption spectroscopy, light-modulated current-voltage measurements, and numerical simulations. Furthermore, spatial mapping reveals pronounced nanoscale variations in the coupled dynamics of carrier transport and interfacial barrier modulation. These results demonstrate that OPP-TR-AFM provides a new framework for resolving the coupled behavior of bulk carriers and interfacial barrier dynamics in van der Waals Schottky junctions with simultaneous spatial and temporal resolution, establishing it as a powerful approach for investigating the microscopic processes that play a crucial role in the development of next-generation optoelectronic devices.
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All authors Munenori Yokota, Hiroyuki Mogi, Yutaka Mera, Katsuya Iwaya, Taketoshi Minato, Shoji Yoshida, Osamu Takeuchi, Tatsuo Nakagawa, Hidemi Shigekawa

Materials Science

Intrinsic Spin Filter Effect in a $d$-wave altermagnet KV$_2$Se$_2$O with Open Fermi Surface

Bin Liu, Pei-Hao Fu, Yu-Xuan Sun et al. (+5 more)

Altermagnets offer a unique pathway to functional spintronics by combining vanishing magnetization with large spin splitting. Here, we demonstrate that the canonical d-wave altermagnet KV2Se2O can deliver giant tunneling magnetoresistance through orientation-dependent spin filtering. By analyzing the crystallographic spin segregation, we show that transport along specific crystallographic axes is nearly fully spin-polarized within the symmetry-protected ballistic channels. We implement this mechanism in a lattice-matched KV2Se2O/Bi2O2Se/KV2Se2O magnetic tunnel junction, which achieves a robust half-metallic transport regime. The symmetry-protected spectral gap in the parallel/anti-parallel configuration ensures a high tunneling magnetoresistance ratio, resulting in substantial tunneling magnetoresistance, robust thermally driven spin filtering, and spin Seebeck effect at room temperature. These findings provide a path of altermagnetic heterostructures as a high-performance platform for scalable, field-free, and thermally stable spin logic.
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All authors Bin Liu, Pei-Hao Fu, Yu-Xuan Sun, Xiao-Lin Zhang, Si-Cong Zhu, Xiang-Long Yu, Hua Wu, Yuan-Zhi Shao

Materials Science

Designing heterostructures to control oxygen stoichiometry in helimagnetic perovskite strontium ferrite

Jennifer Fowlie, Bernat Mundet, Danilo Puggioni et al. (+10 more)

A large challenge in determining the physics of helimagnetic SrFeO3 is in stabilizing the stoichiometric chemical phase over long enough time scales to conduct extensive measurements. Degradation in SrFeO3 manifests mainly as a crossover from metallic to insulating behavior. Using a combination of electronic transport and density functional theory, we show that this degradation is dominated by oxygen loss, possibly on the order of one percent. We further demonstrate that high quality SrFeO3 thin films can be stabilized long-term by combining a nanoscale band insulator capping layer with an ex situ ozone anneal. We show that this produces a nearly-pristine cation sublattice and preserves metallicity for at least several weeks. These results establish a reliable pathway for producing chemically stable SrFeO3 thin films, enabling reproducible studies of its unusual helimagnetism.
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All authors Jennifer Fowlie, Bernat Mundet, Danilo Puggioni, Lopa Bhatt, Eric R. Hoglund, Woo Jin Kim, Jiarui Li, Sang Jun Lee, Wenchi Liu, Antoine Devincenti, James M. Rondinelli, David A. Muller, Harold Y. Hwang

Tuesday 24 February

Materials Science

Seamlessly joining length scales: From atomistic thermal graphs to anisotropic continuum conductivity

C. Ugwumadu, D. A. Drabold and R. M. Tutchton

Thermal transport in complex solids is governed by local structure, defects, and anisotropy, yet most continuum models still rely on oversimplified, homogenized conductivities. Here, we bridge atomistic and continuum descriptions by building finite element (FE) models directly from the site-projected thermal conductivity (SPTC), an atomic-level decomposition of the Green-Kubo thermal conductivity. We introduce a new toolkit, the Simulator Collection for Atomic-to-Continuum Scales (SCACS), which uses a graph neural network to predict SPTC on large atomic structures, coarse-grain these fields into anisotropic conductivity tensors, and embeds them into the heat-flow FE equation with a customized, anisotropy-aware adaptive mesh refinement scheme. Applied to silicon nanostructures, the resulting FE models act as representative volume elements, reproduce bulk conductivities, and capture interfacial and defect-driven anisotropy while maintaining thermodynamic consistency. Additionally, SCACS predicts experimental conductance trends and fields. This innovation demonstrates a novel and general route for transferring atomistic transport information into device-scale thermal simulations with physics-based approximations.
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Materials Science · Cross-listed from cs.LG

Zatom-1: Towards a Multimodal Foundation Model for 3D Molecules and Materials

Alex Morehead, Miruna Cretu, Antonia Panescu et al. (+14 more)

General-purpose 3D modeling in chemistry encompasses molecules and materials, requiring both generative and predictive capabilities. However, most existing AI approaches are optimized for a single domain (molecules or materials) and a single task (generation or prediction), which limits representation sharing and transfer. We introduce Zatom-1, a cross-domain, general-purpose model architecture that unifies generative and predictive learning of 3D molecules and materials. Zatom-1 is a deliberately simplified Transformer trained with a multimodal flow matching objective that jointly models discrete atom types and continuous 3D geometries. This approach supports scalable pretraining with predictable gains as model capacity increases, while enabling fast and stable sampling. We use cross-domain generative pretraining as a universal initialization for downstream multi-task prediction of properties, energies, and forces. Empirically, Zatom-1 outperforms or competes with specialized baselines on both multi-task generative and predictive benchmarks in data-controlled settings, while improving generative inference speed by more than an order of magnitude. Our experiments demonstrate positive predictive transfer between data domains from joint generative pretraining: modeling materials during generative pretraining improves molecular property prediction accuracy. Open-source code and model weights are freely available at https://github.com/Zatom-AI/zatom.
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All authors Alex Morehead, Miruna Cretu, Antonia Panescu, Rishabh Anand, Maurice Weiler, Tynan Perez, Samuel Blau, Steven Farrell, Wahid Bhimji, Anubhav Jain, Hrushikesh Sahasrabuddhe, Pietro Lio, Tommi Jaakkola, Rafael Gomez-Bombarelli, Rex Ying, N. Benjamin Erichson, Michael W. Mahoney

Materials Science

Electrostatic Gating of Ionic Conductance Through Heterogeneous van der Waals Nanopores

Aaron H. Barajas-Aguilar, Matthew Schiel, Ethan Cao et al. (+6 more)

Nanofluidic ionic transistors typically require gate voltages above 1 V and operate only at sub millimolar ionic strengths, limiting their biocompatible applications. We demonstrate ionic transistors consisting of single sub 10 nm nanopores drilled in van der Waals (vdW) heterostructures with internal gate electrodes made of few layer graphene. These devices deliver up to 10fold current modulation at gate voltages as low as 0.3 V in 10 mM KCl, and 2fold modulation at near physiological 100 mM KCl. Baseline conductance with no gate shows surface charge dominated transport below 100 mM KCl consistent with negatively charged hBN walls and 5 nm opening of the pores. The surface charge and the electrochemical asymmetry introduced by the three electrode configuration govern the device behavior: negative gate voltage (VG) enriches ionic concentrations and enhances current, whereas positive VG induces a local depletion zone that suppresses transport. The current modulation by VG is dependent on the polarity of the transmembrane potential and leads to ion current rectification. Molecular dynamics simulations of a nanopore in a hBN graphene hBN stack reveal confinement and surface charge dependent suppression of relative permittivity of interfacial water. Continuum modeling with radially varying interfacial water permittivity reproduces the asymmetric IV characteristics and explains how the embedded gate sculpts local potential and ion concentrations. By enabling sub 0.5 V control of ionic transport at up to 100 mM salt concentrations, these devices address a key barrier in nanofluidics and open the pathway to low power ionic circuits and biosensing.
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All authors Aaron H. Barajas-Aguilar, Matthew Schiel, Ethan Cao, DaVante Cain, Margaret L. Berrens, Fikret Aydin, Tuan Anh Pham, Javier Sanchez-Yamagishi, Zuzanna S. Siwy

Materials Science

Ambient-Pressure Organic Dirac Electron State in $\alpha$-(BETS)$_2$AuCl$_2$

Takuya Kobayashi, Kazuyoshi Yoshimi, Aoto Nishimoto et al. (+2 more)

We report an ambient-pressure Dirac electron (DE) state in a new organic conductor, $\alpha$-(BETS)$_2$AuCl$_2$ (BETS = bis(ethylenedithio)tetraselenafulvalene). This salt exhibits characteristic transport properties, including large positive in-plane and anomalous negative interlayer magnetoresistance. These signatures closely resemble the high-pressure DE states of $\alpha$-(ET)$_2$I$_3$ (ET = bis(ethylenedithio)tetrathiafulvalene). First-principles calculations including spin-orbit coupling identify the electronic state as a quasi-three-dimensional massive Dirac semimetal with residual Fermi pockets. This discovery provides a valuable platform for exploring bulk Dirac fermions without the complexity of high-pressure measurements.
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All authors Takuya Kobayashi, Kazuyoshi Yoshimi, Aoto Nishimoto, Shinji Michimura, Hiromi Taniguchi

Materials Science

Automatic Identification of Compounds in Molecular Mixtures from Liquid-Phase Infrared Spectra

Yannah J.U. Melle, Thanh Nguyen, Jeffrey Lopez et al. (+1 more)

Interpreting spectroscopy data is a critical bottleneck in automating chemical research and industrial characterization. Particularly within infrared (IR) spectroscopy, identifying compounds in complex, liquid-phase chemical mixtures largely relies on expert knowledge, as variable peak assignment, broadening, and shifts hinder data-driven methods. Here, we show that an algorithmic approach can identify components in both simulated and experimental mixture spectra with high accuracy despite nonlinearities in liquid-phase IR data. The method is comprehensively benchmarked with a dataset of over 44,000 simulated liquid-phase IR spectra for mixtures and achieves up to 90% accuracy in identifying molecular components across a dataset of binary and ternary liquid mixtures. Our strategy is robust to perturbation of spectra, and its accuracy is capped by near-identical liquid-phase IR spectra that limit the resolution of chemical identification, imposing theoretical limits on achieving perfect accuracy in structure identification. Finally, we apply the method to automatically interpret IR spectra in experimental settings, correctly identifying the components of nearly all samples within a blind study. This work provides tools and data to advance automated chemical laboratories through algorithmic interpretation of liquid-phase IR spectra of mixtures.
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All authors Yannah J.U. Melle, Thanh Nguyen, Jeffrey Lopez, Daniel Schwalbe-Koda

Materials Science

Non adiabatic dynamics of the ferroelectric soft mode

Gili Scharf, Lara Donval, Leah Ben Gur et al. (+1 more)

Most microscopic descriptions of structural dynamics assume the Born-Oppenheimer separation, where electrons adjust adiabatically to ionic motion. When this separation breaks down, electronic and lattice degrees of freedom can evolve on different timescales, giving rise to new physical phenomena beyond the adiabatic limit. Here we use time-resolved, phase-sensitive second-harmonic generation and pump-probe reflectivity to reshape the ferroelectric free-energy landscape of SnTe while separately tracking polar order and coherent lattice motion. When photoexcitation transiently suppresses the double-well barrier, polarization dynamics become strongly nonlinear, while the coherent phonon dynamics remain harmonic. This decoupling cannot be described by a single adiabatic coordinate for the electronic polarization and ionic positions. We provide a unifying physical description for the non adiabatic dynamics of the ferroelectric mode and the mixed displacive/order-disorder nature of SnTe based on a separation of scales for the renormalization of the ferroelectric stiffness.
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All authors Gili Scharf, Lara Donval, Leah Ben Gur, Alon Ron

Materials Science

Effect of symmetry breaking on altermagnetism in CrSb and Formation of fragmented nodal curves

Arindom Das, Arijit Mandal, Nayana Devaraj et al. (+1 more)

Phenomena concerning altermagnets have opened up a window for unconventional analysis of the momentum space spin polarization (MSSP) of antiferromagnetic materials. Taking the example of one of the widely investigated altermagnets, CrSb, we explore the underlying mechanisms leading to the formation or breaking of altermagnetism. With the aid of DFT calculation and symmetry analysis, we study the behavior of MSSP in the altermagnetic bands of pristine CrSb, along with a few model structures designed from the pristine one by hypothetical vacancy engineering and interstitial doping. We show that the six-fold rotational symmetry of the pristine CrSb can be reduced to a two-fold rotational symmetry via vacancy and doping engineering. We discover the formation of fragmented nodal curves (FNCs) across the Brillouin zone when in an altermagnetic material when the symmetry is restricted to two-fold rotation. Unlike the typical nodal planes and axes, the location of the FNCs in the momentum space is found to be band-specific. The formation of FNCs is further validated by introducing uniaxial strain to CrSb and by examining the band structure of RbMnPO$_4$, as they both exhibit a two-fold rotational symmetry responsible for altermagnetism. We observe that, unlike the pristine case, these FNCs have the potential to manifest anomalous Hall conductivities (AHC), while the Néel vector orients along both in-plane and out-of-plane directions. This flexibility of the AHC will pave the way for the application of altermagnets in the futuristic quantum devices.
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All authors Arindom Das, Arijit Mandal, Nayana Devaraj, B.R.K. Nanda

Materials Science

Anomalous temperature dependence of the electrical resistivity in R$_3$Co$_4$Ge$_{13}$ (R = Y, Lu) single crystals

Juliana Gonçalves Dias, Shyam Sundar, Leticie Mendonça-Ferreira et al. (+1 more)

The presence of strong disorder can significantly impact electrical conduction in metallic systems. Here, we investigate the temperature dependence of the electrical resistivity, $\rho(T)$, in nonmagnetic single crystals of the Remeika-phase cage compounds R$_3$Co$_4$Ge$_{13}$ (R = Y, Lu). Contrary to the density of states (DOS) calculations in the literature, the experimentally measured $\rho(T)$ in both compounds exhibits semiconducting-like behavior, which we attribute to the strong structural disorder due to its unique crystal structure and low carrier-density. A detailed analysis of the electrical resistivity data reveals that neither the Arrhenius thermal activation law nor variable-range hopping (VRH) models can adequately describe their temperature dependence over the broad temperature range of 2-350 K. However, a model incorporating parallel conduction through both semiconducting and metallic channels provides an adequate explanation. In addition to a dominant metallic conduction below $\sim 10$~K, a negative temperature coefficient of the electrical resistivity ($d\rho/dT$) is found in both samples. In the absence of magnetic impurities, the observed $d\rho/dT < 0$ is interpreted in terms of the structural Kondo mechanism.
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All authors Juliana Gonçalves Dias, Shyam Sundar, Leticie Mendonça-Ferreira, Marcos A. Avila

Materials Science

Rapid Primary Radiation Damage Resistance Assessment of Precipitation-Hardened Cu Alloys

Elena Botica-Artalejo, Gregory Wallace and Michael P. Short

This study establishes a direct correlation between in situ irradiation-induced property changes measured by transient grating spectroscopy (TGS) and the resulting microstructural damage in Cu-Cr-Ta alloys. Thin films fabricated by physical vapor deposition were irradiated with 6.6 MeV Cu +3 ions up to 25 DPA, while TGS continuously monitored the evolution of surface acoustic wave (SAW) frequency and thermal diffusivity. Post-irradiation transmission electron microscopy (TEM) was used to quantify void formation as a metric of accumulated radiation damage. A pronounced decrease in SAW frequency was observed some seconds after the onset of irradiation, and it was found to correlate strongly with the final void density. Vacancy MEB calculations propose that the small decrease in SAW frequency is associated with the low population of mobile vacancies, promoting defect recombination and decreasing void formation. This relationship enables early prediction of relative radiation damage resistance within minutes of irradiation, substantially reducing the time required compared to conventional irradiation and postcharacterization routes, allowing rapid screening of multiple compositions. We were able to test this method with 3 compositions of the Cu-Cr-Ta system. More generally, this in situ approach provides an efficient pathway for accelerating the development of materials for radiation environments.
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Materials Science

Symmetr: a Python package for determining symmetry properties of crystals

Jakub Železný

Condensed matter compounds typically form crystals, which break the rotational and translational invariance of space but remain invariant under a discrete set of symmetry operations. Understanding the effects allowed by this symmetry breaking, as well as the constraints imposed by the crystal structure, is a crucial problem in condensed matter physics. Here, we present a Python package for determining the symmetry-restricted forms of tensors describing physical properties of crystals, focusing particularly on magnetic materials. The primary focus is on response tensors; however, the program can also describe equilibrium properties and other physical properties, such as magnetic interactions. The program can describe the symmetry using the conventional magnetic space groups, as well as using the spin groups that describe the non-relativistic limit. Additional functionality includes the treatment of quantities projected onto a particular site and expansions in the magnetic order parameter. The code can be used either from the command line or via a Python API.
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Materials Science · Cross-listed from cond-mat.mes-hall

Observation of sequential quantum oscillations induced by mini-Landau bands in a three-dimensional Dirac semiconductor

Zezhi Wang, Dong Xing, Bingbing Tong et al. (+5 more)

Quantum oscillations, the oscillatory behavior of electrical and thermodynamic properties, are typically observed in metals and vanish in the quantum limit under strong magnetic fields1. Phenomena such as the fractional quantum Hall effect2, the Hofstadter butterfly3,4, and recent observations of quantum oscillations in exotic insulators are notable exceptions5-12. The narrow-gap Dirac semiconductor ZrTe5, a less exotic material without strong correlations or artificially engineered superlattices, nevertheless exhibits resistance oscillations in the quantum limit13 but can be interpreted within a simple Zeeman-effect-based picture14,15, which remains conventional quantum oscillations without exotic properties. Here, we report the observation of unexpected mini-oscillations superimposed on Zeeman-effect-induced main oscillations in the quantum limit. The subtracted mini-oscillations are periodic in 1/B with the highest frequency equal to 2.1% of the first Brillouin zone and have extremely heavy effective mass ~ 2me, which is unexpected in ZrTe5 given its ultralow carrier density. Additionally, the mini-oscillations exhibit sequential features that are synchronized with the main oscillations, suggesting an internal structure of the Landau bands. However, they appear incompatible with the Hofstadter butterfly due to the highly anisotropic/three-dimensional crystal structure. These sequential mini-oscillations correlate with the commensurability resonance effect with subunity fractions observed in angular magnetoresistance, relating to the formation of mini-Landau bands. Our results present solid experimental evidence of exotic quantum oscillations in the quantum limit beyond currently available mechanisms, and establish ZrTe5, a prototypical Dirac semiconductor, as a simple platform parallel to correlated insulators for exploring exotic oscillations.
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All authors Zezhi Wang, Dong Xing, Bingbing Tong, Senyang Pan, Guangtong Liu, Li Lu, Jinglei Zhang, Cheng-Long Zhang

Materials Science

Engineering of SnO2-Graphene Oxide Nano-Heterojunctions for Selective Room-temperature Chemical Sensing and Optoelectronic Devices

Eleonora Pargoletti, Umme H. Hossain, Iolanda Di Bernardo et al. (+6 more)

The development of high-performing sensing materials, able to detect ppb-trace concentrations of volatile organic compounds at low temperatures, is required for the development of next-generation miniaturized wireless sensors. Here, we present the engineering of selective room-temperature chemical sensors, comprising highly porous tin dioxide (SnO2) - graphene oxide (GO) nano-heterojunction layouts. The optoelectronic and chemical properties of these highly porous (above 90%) p-n heterojunctions were systematically investigated in terms of composition and morphologies. Optimized SnO2-GO layouts demonstrate significant potential as both visible-blind photodetectors and as selective room-temperature chemical sensors. Notably, a low GO content results in an excellent UV light responsivity (400A x W-1), with short rise and decay times, and room-temperature high chemical sensitivity with selective detection of volatile organic compounds such as ethanol down to 100~ppb. In contrast, a high concentration of GO drastically decreases the room-temperature response to ethanol and results in good selectivity to ethylbenzene. The feasibility of tuning the chemical selectivity of the sensor response by engineering the relative amount of GO and SnO2 is a promising feature that may guide the future development of miniaturized solid-state gas sensors. Furthermore, the excellent optoelectronic properties of these SnO2-GO nano-heterojunctions may find applications in various other areas such as optoelectronic devices and (photo)electrocatalysis.
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All authors Eleonora Pargoletti, Umme H. Hossain, Iolanda Di Bernardo, Hongjun Chen, Thanh Tran-Phu, Gian Luca Chiarello, Josh Lipton-Duffin, Antonio Tricoli, Giuseppe Cappelletti

Materials Science

Determining Atomic Structure from Spectroscopy via an Active Learning Framework

Ian Slagle, Faisal Alamgir and Victor Fung

Determining atomic structure from spectroscopic data is central to materials science but remains restricted to a limited set of techniques and material classes, largely due to the computational cost and complexity of structural refinement. Here we introduce ActiveStructOpt, a general framework that integrates graph neural network surrogate models with active learning to efficiently determine candidate structures that reproduce target spectra with minimal computational expenditure. Benchmarking with X-ray pair distribution function data, and with the more computationally demanding simulations of X-ray absorption near-edge spectra (XANES) and extended X-ray absorption fine structure (EXAFS), demonstrate that ActiveStructOpt reliably determines structures that match closely in spectra across diverse materials classes. Under equivalent computational budgets, ActiveStructOpt outperforms existing structure determination methods. By enabling data-efficient, multi-objective structural refinement across a broad range of computable spectroscopic techniques, ActiveStructOpt provides a flexible and extensible approach to atomic structure determination in complex materials.
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Materials Science

A One-Dimensional Reduction Method for Calculating Thermal Expansion in Solids: Application to Orthorhombic Systems

Dmitry Vasilyev

Anisotropic thermal expansion plays a critical role in the performance and reliability of functional materials, yet its theoretical description remains limited. Here, a computational framework that reduces the calculation of thermal expansion in solids to an effective one-dimensional problem is presented and applied to orthorhombic lattice. Using this method, a comprehensive set of thermodynamic and mechanical properties is determined.
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Materials Science

Ferromagnetism above 200 K in organic-ion intercalated CrSBr

Sofia Ferreira-Teixeira, Daniel Tezze, Maria Ramos et al. (+11 more)

CrSBr is a van der Waals magnetic semiconductor exhibiting antiferromagnetic order below 140 K. It has emerged as a promising platform for engineering 2D magnetism because its intertwined electronic, optical, and magnetic properties can be profoundly modified via external stimuli such as electrical gating or magnetic fields. However, other strategies for tuning magnetism in layered materials, such as molecular intercalation, remain largely unexplored for CrSBr. Here, we demonstrate that the intercalation of tetramethylammonium (TMA) and tetrapropylammonium (TPA) ions into CrSBr induces a transition from antiferromagnetic to ferromagnetic order, while significantly enhancing the magnetic transition temperature to 190 K (TMA) and 230 K (TPA). The resulting intercalates are air-stable and exhibit large, hysteretic magnetoresistance exceeding 60% at 50 K in the TPA case. Besides, intercalation introduces symmetry-breaking structural changes in each CrSBr plane, revealed by Raman microscopy and corroborated by density functional theory (DFT) calculations. These findings highlight molecular intercalation as a powerful and versatile route to tailor the magnetic properties of CrSBr and unlock its potential to fabricate robust, high-temperature 2D magnetic devices.
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All authors Sofia Ferreira-Teixeira, Daniel Tezze, Maria Ramos, Covadonga Álvarez-García, Bertuğ Bay{\i}nd{\i}r, Junhyeon Jo, Beatriz Martín-García, Maider Ormaza, Fèlix Casanova, Samuel Mañas-Valero, Eugenio Coronado, Hasan Sahin, Luis E. Hueso, Marco Gobbi