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Physics Condensed Matter Materials Science

cond-mat.mtrl-sci Watch Materials Science

Saturday 21 March

Materials Science · Cross-listed from cond-mat.soft

Convective Preheating Enhances Front Propagation in DCPD Frontal Polymerization

M Vijay Kumar, Saujatya Mandal, Siddhant Jain et al. (+2 more)

Frontal polymerization (FP) enables rapid curing of thermosets via a self-sustaining thermal wave, but its propagation mechanism can shift dramatically depending on processing conditions. In this study, we investigate the effect of trigger direction and monomer viscosity - controlled via hold time - on the front velocity in frontal ring-opening metathesis polymerization (FROMP) of dicyclopentadiene (DCPD). Our experiments reveal that at low viscosities, bottom-triggered FP fronts propagate significantly faster, ~50% faster front speed compared to top-triggered ones, driven by buoyancy-enhanced convection that preheats the unreacted monomer ahead of the front, that can have important implications for manufacturing applications. However, with increasing hold time, the monomer viscosity rises steeply, suppressing convection and causing the front velocity for top and bottom triggering to converge. This behavior reflects a convection-to-conduction (thermal-diffusion) transition in heat transport during FP. Complementary simulations incorporating buoyancy-driven advection reproduce the observed trends and highlight the importance of fluid flow in front dynamics. These results provide new insight into the coupled thermo-fluid-chemical mechanisms in FP offer strategies to tailor front behavior through viscosity and initiation geometry.
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All authors M Vijay Kumar, Saujatya Mandal, Siddhant Jain, Saptarshi Basu, Debashish Das

Materials Science · Cross-listed from physics.geo-ph

A quiet quantum revolution in Earth's deep interior

Renata Wentzcovitch, Laura Cobden, Christine Houser et al. (+2 more)

The Earth's lower mantle hosts a subtle but pervasive quantum phenomenon: the pressure-induced spin crossover of iron in its dominant minerals, bridgmanite and ferropericlase. In this transition, iron ions gradually shift from high-spin to low-spin electronic states without structural change, altering their volume, compressibility, and elastic properties. Although long recognized experimentally and theoretically, its geophysical significance has only recently become clear through the integration of mineral physics and three-dimensional seismic imaging. The spin crossover reduces bulk modulus and P-wave velocities while leaving S-wave speeds largely unaffected, producing a distinctive decoupling between P- and S-wave anomalies. This signature is now observed in global tomography and reconciles seismic observations with realistic mantle temperatures and compositions. Rather than forming a sharp boundary, the crossover extends across most of the lower mantle, acting as a diffuse yet essential control on seismic structure. This work highlights how quantum-scale electronic transitions influence planetary-scale dynamics and interpretations of Earth's deep interior.
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All authors Renata Wentzcovitch, Laura Cobden, Christine Houser, Grace Shephard, Jingyi Zhuang

Materials Science

Temperature-dependent vibrational EELS simulations with nuclear quantum effects

Zuxian He and Ján Rusz

The Time Autocorrelation of Auxiliary Wave (TACAW) method has established a framework for modeling angle-resolved electron energy loss spectroscopy (EELS) of phonons and magnons by deriving scattering intensities from the time autocorrelation of the beam wavefunction. This approach enables efficient computation of scattering intensities while naturally accounting for dynamical diffraction and multiple-scattering effects. In the cryogenic regime, vibrational spectra are dominated by nuclear quantum effects, notably zero-point motion. To capture these effects in low-temperature vibrational EELS, we incorporate thermostatted ring polymer molecular dynamics (TRPMD) into the TACAW formalism. Our results demonstrate that nuclear quantum effects lead to significant deviations from classical molecular dynamics predictions in the vibrational spectra of silicon at low temperatures and correctly predict the nearly temperature-independent optical phonon peak intensities in silicon, consistent with the first Born approximation. The TRPMD-TACAW method provides a robust theoretical tool for probing the low-temperature limit of vibrational EELS, offering a necessary benchmark for the quantitative analysis of emerging cryogenic scanning transmission electron microscopy experiments.
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Materials Science

Electric-field-induced X-ray Nonreciprocal Dichroism in Hematite

Takeshi Hayashida, Koei Matsumoto, Keito Arakawa et al. (+5 more)

Hematite (alpha-Fe2O3) is a prototypical room temperature antiferromagnet whose time-reversal-odd magnetic structure has recently attracted renewed attention. While such magnetic symmetry can be characterized in terms of higher-order multipoles beyond the magnetic dipole, their manifestation in measurable physical phenomena has remained largely elusive. In this work, we investigate x-ray absorption near the Fe K-edge of hematite under an applied electric field, which explicitly breaks space-inversion symmetry. We observe an electric-field-induced x-ray nonreciprocal linear dichroism (E-induced XNLD) that reflects the time-reversal-odd nature of the magnetic order. Numerical simulations based on ab-initio density functional theory reproduce the observed spectra, including their dependence on the antiferromagnetic domain and x-ray polarization. Furthermore, a symmetry-resolved multipole analysis reveals that this response originates from the magnetic quadrupole and the magnetic toroidal octupole induced by the applied electric field. These results demonstrate that electric-field-modulated x-ray absorption provides direct access to the antiferroic order of higher-order multipoles in time-reversal-odd antiferromagnets, thereby establishing a general framework to uncover hidden symmetry properties in magnetic materials.
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All authors Takeshi Hayashida, Koei Matsumoto, Keito Arakawa, Yves Joly, Sergio Di Matteo, Kenji Tamasaku, Yoshikazu Tanaka, Tsuyoshi Kimura

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

Many-body electronic structure, self-doped double-exchange, and Hund metallicity in 1T-CrTe2 bulk and monolayer

Dong Hyun David Lee, Hyeong Jun Lee, Taek Jung Kim et al. (+2 more)

The van der Waals (vdW) ferromagnet 1T-CrTe2 is an emerging spintronics platform, notable for its high Curie temperature (Tc) and intriguing transport properties. However, the fundamental interplay between the electron correlations and magnetism underlying its high Tc still remains elusive. Here, using density functional theory plus dynamical mean-field theory (DFT+DMFT), we identify 1T-CrTe2 as a self-doped double-exchange ferromagnet with pronounced Hund metallicity. This identification is grounded in the first detailed analysis of its many-body electronic structure, which reveals a dual electronic nature of Cr-d orbitals where itinerant eg electrons coexist with localized t2g moments. The interaction between these orbitals, mediated by Hund's coupling, drives the double-exchange ferromagnetism, establishing 1T-CrTe2 as a Hund metal reminiscent of orbital-selective Mott systems. In the monolayer limit, while this physical picture persists, structural deformation, rather than reduced dimensionality, notably reduces Tc.Our findings offer a new perspective on the high-Tc ferromagnetism in 1T-CrTe2, a mechanism potentially pivotal for other correlated two-dimensional vdW metallic magnets.
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All authors Dong Hyun David Lee, Hyeong Jun Lee, Taek Jung Kim, Min Yong Jeong, Myung Joon Han

Materials Science

Crystal Growth and anisotropic magneto-transport properties of semimetallic LaNiSb3

Haribrahma Singh, Aarti Gautam, Prabuddha Kant Mishra et al. (+2 more)

Single crystals of LaNiSb$_3$ were grown using the Sn flux method. Structural characterization confirms that LaNiSb$_3$ crystallizes in the orthorhombic $Pbcm$ space group with lattice parameters $a = 13.0970(2)\,\mathrm{\AA}$, $b = 6.1400(4)\,\mathrm{\AA}$, and $c = 12.1270(4)\,\mathrm{\AA}$. Electrical resistivity measurements demonstrate metallic behavior over the entire temperature range of 3–300~K. The magnetoresistance exhibits a positive anisotropic response, attaining a maximum of $\sim 8\%$ for $H \parallel b$, with a pronounced crossover from quadratic to nearly linear field dependence. Angular-dependent MR measurements reveal a pronounced twofold symmetry upon magnetic field rotation within both the $ab$ and $ac$ crystallographic planes up to 50~K, indicating anisotropic charge transport. Hall resistivity measurements show predominantly electron-type conduction at high temperatures, with an increasing hole contribution upon cooling. The multiband character is further corroborated by the violation of Kohler's scaling and is well described within a semiclassical two-band framework. Collectively, these results suggest that LaNiSb$_3$ exhibits anisotropic multiband electronic transport and is a compelling candidate for exploring structure–property correlations in topological semimetals.
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All authors Haribrahma Singh, Aarti Gautam, Prabuddha Kant Mishra, Rie Y. Umetsu, Ashok Kumar Ganguli

Materials Science

Emerging hierarchical dislocation structures: Insights from scanning electron microscopy-electron backscatter diffraction in situ tensile testing and multifractal analysis

Mikhail Lebyodkin, Maxim Gussev, Jamieson Brechtl et al. (+1 more)

Understanding the evolution of dislocation structures during plastic deformation is critical for predicting the mechanical performance of metallic materials. In this work, we applied in situ scanning electron microscopy/electron backscatter diffraction tensile testing combined with multifractal (MF) analysis to assess deformation-induced dislocation structure evolution in solution-annealed 304L stainless steel, both in its as-received and neutron-irradiated states (5.4 displacements per atom). The analysis of kernel average misorientation patterns revealed the formation of hierarchical dislocation arrangements that exhibit clear MF scaling behavior. Despite pronounced visual differences between nonirradiated and irradiated specimens – most notably, the appearance of dislocation channels after irradiation – the singularity spectra suggest that both conditions give rise to similar underlying hierarchical structures. MF analysis provides a quantitative measure of the spatial complexity and self-organization of dislocation patterns, highlighting the accelerated emergence and evolution of the dislocation structures in irradiated polycrystalline materials, as well as the limitation of their spatial extent. The findings indicate that irradiation not only modifies microstructure but also alters correlation-driven dislocation organization. More generally, they demonstrate that MF analysis is a powerful tool for probing mesoscale deformation mechanisms.
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All authors Mikhail Lebyodkin, Maxim Gussev, Jamieson Brechtl, Tatiana Lebedkina

Materials Science

Substrate-Mediated Evaporation and Stochastic Evolution of Supported Au Nanoparticles

Dmitri N. Zakharov, Xiaohui Qu, Hong Wang et al. (+6 more)

We use in situ transmission electron microscopy with automated tracking to study supported gold nanoparticles (NPs) during high-temperature vacuum annealing. \rev{The average mass loss per NP is governed by a flat, nearly size-independent substrate-mediated evaporation profile.} On top of \rev{this mean shrinkage}, individual NPs show significant fluctuations in apparent growth or shrinkage, and NP volume follows a \rev{random-walk-like trajectory. To rationalize both the ensemble-mean behavior and the particle-resolved variability, we develop a self-consistent theory that couples substrate-mediated evaporation to collective 2D Ostwald-type mass exchange through a shared adatom field, described in terms of a renormalized screening length and background concentration. In the experimentally relevant regime, the theory predicts an approximately size-independent mean shrinkage rate and clarifies how net mass loss suppresses classical coarsening.} \rev{Superimposed on this deterministic drift, we quantify stochastic volume trajectories and capture their fluctuation spectrum with a minimal Langevin description consistent with intermittent adatom attachment and detachment events.} In addition, we characterize the lateral diffusive motion of NPs, which is responsible for their coalescence. Altogether, our results highlight that stochasticity is intrinsic at the nanoscale \rev{and that predicting the evolution of supported NPs at early and intermediate times requires a unified framework combining substrate-mediated evaporation, collective mass exchange, and stochastic fluctuations.
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All authors Dmitri N. Zakharov, Xiaohui Qu, Hong Wang, Yuewei Lin, Aaron Stein, James P. Horwath, Shinjae Yoo, Eric A. Stach, Alexei V. Tkachenko

Materials Science · Cross-listed from cs.SE

Evaluating LLM-generated code for domain-specific languages: molecular dynamics with LAMMPS

Ethan Holbrook, Juan C. Verduzco and Alejandro Strachan

Large language models (LLMs) are changing the way researchers interact with code and data in scientific computing. While their ability to generate general-purpose code is well established, their effectiveness in producing scientifically valid scripts for domain-specific language (DSLs) remains largely unexplored. We propose an evaluation procedure that enables domain experts to assess the validity of LLM-generated input files for LAMMPS, a widely used molecular dynamics (MD) code, without requiring deep familiarity with its syntax. The evaluation procedure combines a normalization step that produces canonical input files with an extensible parser for syntax analysis, followed by a reduced-cost execution stage and accuracy checks that isolate common errors before running costly simulations. We apply the pipeline to eight state-of-the-art LLMs across three prompts of increasing complexity. The parser pass rate has improved from 74% to 91% over the past year, but scientific accuracy on coupled multi-step workflows remains limited. Across all 80 scripts evaluated on the most complex prompt, only one was fully correct as generated. We further package the automated stages as a reusable agentic skill that LLMs can invoke during script generation; in a small-scale demonstration, this skill helped two models produce five fully correct scripts out of six across the same three prompts, including the hardest one. The pipeline highlights both the limitations of current LLMs in generating scientific DSLs and a practical path toward integrating them into domain-specific computational ecosystems.
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Friday 20 March

Materials Science

Composition dependence of the critical Rayleigh number curve for macrosegregation in multicomponent metal alloys

Owain S. Houghton, Adrian S. Sabau and Gregory B. Olson

Convective instabilities in the semi-solid mushy zone can trigger channel formation that leads to defects known as freckles, channel segregates and A-type segregates. In the present work, Flemings' model is used to determine conditions for the onset of local remelting when buoyancy-driven flow is suddenly triggered in an initially stagnant mushy zone. An expression in the form of a Rayleigh number $Ra$, and its associated critical value $Ra_{\rm crit}$, above which the local remelting condition is satisfied, are derived. Using thermophysical data from CALPHAD, these expressions are evaluated using results from benchmark experimental and numerical studies for the nickel-based superalloy SX-1 and Pb-Sn alloys. The correlation of this local-remelting criterion with previously reported empirical criteria is also tested for various steel compositions. It is found that $Ra_{\rm crit}$ varies with the local average solid fraction and several thermophysical properties. Since these properties can vary substantially within a relatively narrow composition range, it is suggested that $Ra_{\rm crit}$ is a strongly composition-dependent parameter.
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Materials Science · Cross-listed from cond-mat.str-el

Magnetic and electric properties of the metallic kagome antiferromagnet CrRhAs

Franziska Breitner, Bin Shen, Anton Jesche et al. (+2 more)

CrRhAs is an antiferromagnetic kagome metal predicted to host a nontrivial spin texture with vector spin chirality [Huang et al., npj Quantum Mater. 8, 32 (2023)]. We report the synthesis and basic characterization of CrRhAs single crystals, which exhibit an antiferromagnetic transition with $T_{\rm N}$ = 150~K, evidenced by electrical transport, heat capacity, and magnetization measurements. Hall resistivity varies linearly with magnetic field, i.e., there is no nonlinear Hall contribution. Intriguingly, the Hall coefficient changes sign between the configurations of $j \parallel ab, H \perp ab$ and $j \parallel c, H \perp c$, which is likely connected to a peculiar topology of the Fermi surface. Furthermore, for $j \parallel ab$, the Hall coefficient shows a pronounced and continuous enhancement below $T_{\rm N}$, signaling a significant reconstruction of the Fermi surface or an extra scattering from the magnons. Our results offer guidance for exploring anomalous electric transport phenomena in exotic magnetic systems.
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All authors Franziska Breitner, Bin Shen, Anton Jesche, Alexander A. Tsirlin, Philipp Gegenwart

Materials Science · Cross-listed from physics.app-ph

Degradation Dynamics of Perovskite Solar Cells Under Fixed Reverse Current Injection

Fangyuan Jiang, Haruka Koizumi, Hannah Contreras et al. (+8 more)

Previous studies of reverse-bias stability in perovskite solar cells have focused primarily on voltage controlled reverse-bias tests. Here we instead present an investigation of perovskite solar cell degradation under well-defined, constant reverse-current stress. We show that the choice of hole-transport layer dictates the dominant degradation pathway: cells using thick poly(triphenylamine) (PTAA) layers with better indium-doped tin oxide (ITO) coverage can tolerate high reverse bias but quickly undergo catastrophic breakdown under fixed reverse current near their one-sun maximum power-point. In contrast, cells modified with the phosphonic-acid interface layer MeO-2PACz, with poorer ITO coverage compared to PTAA, exhibit soft, gradual, and largely recoverable degradation, regardless of the shading conditions. For MeO-2PACz devices, degradation increases with both current magnitude and duration. Importantly, when normalized by injected charge (current times duration), lower currents applied over longer times cause more severe degradation than higher currents over shorter periods. Combining electrical measurements with spatially resolved photoluminescence imaging, we argue against shunt formation and instead support an ion- and charge-mediated interfacial electrochemical degradation mode.
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All authors Fangyuan Jiang, Haruka Koizumi, Hannah Contreras, Rajiv Giridharagopal, Akash Dasgupta, Zixu Huang, Ryan A. DeCrescent, Kell Fremouw, Michael D. McGehee, Neal R. Armstrong, David S. Ginger

Materials Science · Cross-listed from physics.app-ph

Neutralization of the impact of belt speed on screen printed copper metallization by LECO on PERC homogeneous emitter

Abasifreke Ebong, Donald Intal, Sandra Huneycutt et al. (+6 more)

Copper fire-through metallization is a cost-effective alternative to Ag counterpart for industrial high efficiency solar cells. The fire through dielectric metallization relies on belt speed, which dictates the ramp up and ramp down rates for effective contact formation. In this paper three belt speeds (325oC, 360oC, 390oC) at constant peak firing temperature, were used to process PERC (homogeneous emitter) cells. After the contact firing the electrical parameters were dependent on belt speed, but after LECO treatment, they were identical. The SEM/EDS cross sectional analyses showed increased elemental Cu with belt speed, and the series resistance was lowest for the middle belt speed before LECO. However, after the LECO treatment, the series resistance dropped, respectively, to 0.503 ohm-cm-2, 0.428 ohm-cm-2 and 0.500 ohm-cm-2 leading to efficiency of 20.8% on homogeneous PERC emitter.
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All authors Abasifreke Ebong, Donald Intal, Sandra Huneycutt, Ajeet Rohatgi, Vijay Upadhyaya, Sagnik Dasgupta, Ruohan Zhong, Thad Druffel, Ruvini Dharmadasa

Materials Science · Cross-listed from physics.app-ph

Critical look at the atmospheric Cu fire-through dielectric metallization for cost-effective and high efficiency silicon solar cells

Donald Intal, Sandra Huneycutt, Abasifreke Ebong et al. (+6 more)

The formation of stable copper-silicide (Cu3Si) interfaces is crucial for cost-effective, high-efficiency solar cells. However, copper's diffusivity and electromigration issues pose challenges for contact stability. This study employs Laser-Enhanced Contact Optimization (LECO) to induce localized nano-scale Joule heating at the Cu-Si interface in phosphorus-doped p-PERC solar cells. High-resolution STEM and bright field analyses confirm stable Cu3Si formation in LECO-treated samples, with significantly reduced material segregation compared to nonLECO samples. SEM and post-etch EDS mapping demonstrate improved chemical resistance and interface cleanliness. Electrically, LECO treatmenet reduces series resistance by a factor 3, enhancing fill factor and efficiency while preserving diode quality. These results highlight LECO as a scalable method for reliable, silver-free solar cell metallization.
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All authors Donald Intal, Sandra Huneycutt, Abasifreke Ebong, Ajeet Rohatgi, Vijay Upadhyaya, Sagnik Dasgupta, Ruohan Zhong, Thad Druffel, Ruvini Dharmadasa

Materials Science · Cross-listed from physics.chem-ph

A unified machine-learning framework for ab initio multiscale modeling of liquids

Anna T. Bui and Stephen J. Cox

Understanding and predicting the behavior of liquid matter across length scales, using only the microscopic interactions encoded in the Schrödinger equation, remains a central challenge in the physical sciences. Achieving this goal requires not only an accurate and efficient description of intermolecular forces but also a consistent framework that bridges the micro-, meso-, and macroscales. Here, by combining machine-learned interatomic potentials (MLIPs) with neural classical density functional theory (neural cDFT), we present such a framework. The underlying idea is simple: MLIPs trained on quantum-mechanical energies and forces are used to generate inhomogeneous microscopic density profiles, which in turn serve as the training data for neural cDFT. The resulting ab initio neural cDFT is not only significantly more computationally efficient than molecular simulations, but also provides a conceptually transparent route to the thermodynamics of both homogeneous and inhomogeneous systems. We demonstrate the approach for both water and carbon dioxide using several exchange-correlation functionals. Beyond accurately reproducing bulk equations of state and liquid-vapor phase diagrams, ab initio neural cDFT predicts, from first principles, how confinement modifies liquid-vapor coexistence in water. It also captures complex behavior in supercritical carbon dioxide such as the Fisher-Widom and Widom lines. Ab initio neural cDFT establishes a general first-principles route to multiscale modeling of fluids within a single unified conceptual framework.
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Materials Science

Structural Phase Separation Couples to Charge-Density-Wave Formation in Kagome Metal FeGe

Boyang Zhao, Youngjun Ahn, Qinwen Deng et al. (+7 more)

The intertwining of charge, spin, and lattice degrees of freedom underlies the emergent properties of correlated materials. A recent prominent example is the kagome metal FeGe, which hosts coexisting charge density wave (CDW) and antiferromagnetic orders, accompanied by a lattice distortion associated with partial Ge-Ge dimerization. Using temperature-dependent high-resolution X-ray diffraction measurements, we observed a robust splitting of the lattice reflection into two coexisting peaks with distinct lattice constants at the CDW transition temperature TCDW, providing direct evidence for a first-order structural phase transition that is absent in samples with suppressed CDW order. Furthermore, the long-range CDW order was found to be only commensurate with lattice structures with the compressed out-of-plane lattice constant. The Landau free energy analysis shows that strong lattice-charge coupling is a key factor in stabilizing long-range CDW order. Our work clarifies the critical role of structural transformation in the CDW formation and opens opportunities for strain control of electronic phases in FeGe.
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All authors Boyang Zhao, Youngjun Ahn, Qinwen Deng, Yidai Liu, Sijie Xu, Donald A. Walko, Stephan O. Hruszkewycz, Pengcheng Dai, Liang Wu, Haidan Wen

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

Gate-tunable synthetic antiferromagnetism with nonrelativistic spin splitting in a graphene/MnS/graphene heterostructure

Marko Milivojević and Martin Gmitra

We propose encapsulating type-A antiferromagnetic semiconductors between graphene layers to realize a gate-tunable synthetic antiferromagnet with nonrelativistic spin splitting, enabling efficient spintronic transport via graphene. Ab initio calculations and tight-binding models of graphene/MnS/graphene heterostructure reveal that gate-tuning of the heterostructure breaks top/bottom graphene equivalence, inducing opposite ferromagnetic proximity exchange that lifts spin degeneracy to yield nonrelativistic spin splitting at the Fermi level, dominating over relativistic effects. The induced effects manifest as conductance dips in spin-resolved transport through proximitized graphene nanoribbons, observable as giant magnetoresistance within a narrow energy window around the Fermi level. Our graphene/type-A antiferromagnetic heterostructure, a readily synthesizable platform incorporating antiferromagnets with nonrelativistic spin splitting, pave the way for gate-manipulated, low-dimensional antiferromagnetic devices.
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Materials Science

A chemical language model for reticular materials design

Dhruv Menon, Vivek Singh, Xu Chen et al. (+7 more)

Reticular chemistry has enabled the synthesis of tens of thousands of metal-organic frameworks (MOFs), yet the discovery of new materials still relies largely on intuition-driven linker design and iterative experimentation. As a result, researchers explore only a small fraction of the vast chemical space accessible to reticular materials, limiting the systematic discovery of frameworks with targeted properties. Here, we introduce Nexerra-R1, a building-block chemical language model that enables inverse design in reticular chemistry through the targeted generation of organic linkers. Rather than generating complete frameworks directly, Nexerra-R1 operates at the level of molecular building blocks, preserving the modular logic that underpins reticular synthesis. The model supports both unconstrained generation of low-connectivity linkers and scaffold-constrained design of symmetric multidentate motifs compatible with predefined nodes and topologies. We further combine linker generation with flow-guided distributional targeting to steer the generative process toward application-relevant objectives while maintaining chemical validity and assembly feasibility. The generated linkers are subsequently assembled into three-dimensional frameworks and are structurally optimized to produce candidate materials compatible with experimental synthesis. Using Nexerra-R1, we validate this strategy by rediscovering known MOFs and by proposing the experimental synthesis of a previously unreported framework, CU-525, generated entirely in silico. Together, these results establish a general inverse-design paradigm for reticular materials in which controllable chemical language modelling enables the direct translation from computational design to synthesizable frameworks.
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All authors Dhruv Menon, Vivek Singh, Xu Chen, Mohammad Reza Alizadeh Kiapi, Ivan Zyuzin, Hamish W. Macleod, Nakul Rampal, William Shepard, Omar M. Yaghi, David Fairen-Jimenez

Materials Science · Cross-listed from quant-ph

One-to-one quantum simulation of a frustrated magnet with 256 qubits

Lucas Leclerc, Sergi Julià-Farré, Gabriel Silva Freitas et al. (+33 more)

Analog quantum simulators offer a powerful microscopic probe of quantum many-body systems, yet have largely been benchmarked against model Hamiltonians rather than real materials. Here, we use a 256-qubit Rydberg simulator to implement the effective Hamiltonian of the frustrated triangular-lattice magnet TmMgGaO$_4$. Simulated magnetization curves agree quantitatively with susceptibility measurements on single crystals, and both platforms consistently determine the antiferromagnetic phase transition. Snapshot-resolved analysis confirms that quantum fluctuations, rather than disorder, govern the intermediate paramagnetic regime. Having established this correspondence, we access non-equilibrium dynamics following a sudden quench, a regime at picosecond material timescales where entanglement growth places the problem beyond classical reach. The simulator reveals thermalization of local observables, demonstrating that analog quantum simulation can reproduce and extend the physics of a real material.
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All authors Lucas Leclerc, Sergi Julià-Farré, Gabriel Silva Freitas, Guillaume Villaret, Boris Albrecht, Lucas Béguin, Lilian Bourachot, Clémence Briosne-Frejaville, Dorian Claveau, Antoine Cornillot, Julius de Hond, Djibril Diallo, Clément Dupays, Robin Dupont, Thomas Eritzpokhoff, Emmanuel Gottlob, Loïc Henriet, Michael Kaicher, Lucas Lassablière, Arvid Lindberg, Yohann Machu, Hadriel Mamann, Thomas Pansiot, Julien Ripoll, Eun Sang Choi, Adrien Signoles, Joseph Vovrosh, Bruno Ximenez, Vivien Zapf, Shengzhi Zhang, Haidong Zhou, Minseong Lee, Tiagos Mendes-Santos, Constantin Dalyac, Antoine Browaeys, Alexandre Dauphin

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

Competing skin effect and quasiperiodic localization in the non-Hermitian Su-Schrieffer-Heeger chain: Reentrant delocalization, spectral topology destruction, and entanglement suppression

Souvik Ghosh

We investigate the interplay between the non-Hermitian skin effect and Aubry-André-Harper (AAH) quasiperiodic disorder in a one-dimensional Su-Schrieffer-Heeger (SSH) chain with nonreciprocal hopping. By exact diagonalization, transfer-matrix analysis, and an analytical similarity-transformation argument, we map the full ( , $\delta$) phase diagram, where A is the AAH modulation strength and the nonreciprocity parameter. We identify five distinct regimes: ( ) topological with extended bulk, (II) AAH-localized, (III) skin-localized, (IV) fully localized, and a previously unreported (V) competition regime exhibiting reentrant partial delocalization, in which intermediate quasiperiodic disorder disrupts the directional skin accumulation before ultimately Anderson-localizing all states. Using phase-averaged diagnostics and finite-size scaling, we confirm that the reentrant regime is robust, characterized by a non-monotonic inverse participation ratio that sharpens with increasing system size. We derive an analytical expression for the modified localization boundary $\lambda_{c}(\delta)=2\sqrt{v_{eff}w}$ with $v_{vff}=\sqrt{v^{2}-\delta^{2}}$, which agrees with numerical Lyapunov exponent calculations. We further show that quasiperiodic disorder progressively unwinds the complex spectral loops, destroying the point-gap topology at a critical strength distinct from the band-topological transition ; that the skin effect suppresses entanglement entropy to near-zero values while sufficiently strong AAH disorder partially restores it ; and that the SSH sublattice structure absent in the widely studied non-Hermitian AAH chain is essential for producing the five-phase landscape, as demonstrated by direct comparison with the non-dimerized limit.
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Materials Science

When Cubic Is Not Isotropic: Phonon-Exciton Decoupling in CuInSnS$_4$ Single Crystals

Lara Kim Linke, Yvonne Tomm, Xinyun Liu et al. (+9 more)

Atomic-scale disorder can create hidden optical anisotropy even in crystals that are structurally cubic on average. Here, we show that CuInSnS$_4$ single crystals host locally symmetry-broken environments arising from intrinsic In/Sn cation disorder, which affect vibrational and excitonic properties in markedly different ways. Combining polarization- and temperature-dependent Raman spectroscopy, infrared near-field microscopy, steady-state and time-resolved photoluminescence, and first-principles calculations, we find that phonons remain largely symmetry-averaged and locally homogeneous on the nanoscale. In contrast, photoluminescence reveals a lower-energy band-tail emission with pronounced polarization anisotropy following a well-defined angular symmetry, highlighting the strong sensitivity of excitonic states to local symmetry breaking. This phonon-exciton decoupling reveals that intrinsic disorder can localize excitons while preserving vibrational coherence and dielectric homogeneity, thereby opening new opportunities for polarization-sensitive light sources, anisotropic photodetectors, and exciton-based optical functionalities even in nominally cubic multinary semiconductors.
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All authors Lara Kim Linke, Yvonne Tomm, Xinyun Liu, Galina Gurieva, Daniel M. Tobbens, Pardis Adams, Michel Calame, Ryan W. Crisp, Jessica Boland, Sean Kavanagh, Susan Schorr, Mirjana Dimitrievska

Materials Science

Transformer-based prediction of two-dimensional material electronic properties under elastic strain engineering

Haoran Ma, Yuchen Zheng, Leining Zhang et al. (+2 more)

Strain engineering provides a powerful route for tuning the electronic properties of two-dimensional (2D) materials, but exploring the full multidimensional strain space with density functional theory (DFT) is computationally prohibitive due to the nonlinear coupling between normal and shear components. In this work, we introduce a Transformer-based, multi-target surrogate model framework that achieves DFT-level bandgap prediction accuracy, reaching a mean absolute error of 0.0103 eV while retaining full interpretability through attention-weight analysis. The learned self-attention map consistently identifies shear strain as the interaction center that influences both bandgap and phonon stability, an insight not readily captured by classical feature-importance metrics. This work establishes attention-based architectures as physically interpretable surrogate models for multi-property prediction, offering a generalizable strategy for accelerating deep elastic strain engineering in materials informatics.
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All authors Haoran Ma, Yuchen Zheng, Leining Zhang, Xiaofei Chen, Dan Wang

Materials Science

Theory of Dendritic Crack Growth in Ceramic Solid-State Batteries

Ansgar Lowack

In solid-state batteries, ceramic solid electrolytes are penetrated by dendrites when plating above a critical current density $J_\mathrm{crit}$. A dendrite will propagate by metal deposition at a pre-existing dendrite tip if the mechanical energy required to crack the ceramic open is less than the electrical energy (Joule heating) wasted by forcing the current to detour around the dendrite to the flat electrode surface. Based on this principle of minimal power dissipation, a dependence of $J_\mathrm{crit}\propto c_\mathrm{max}^{3/2}$ is derived in an analytical fashion. $c_\mathrm{max}$ is the length of the longest pre-existing, sufficiently thin interfacial defect. Consequentially, scattering of dendrite growth between samples must follow a Weibull-distribution, similar to the tensile strength of ceramic components but at smaller Weibull-modulus.
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Materials Science · Cross-listed from quant-ph

Bright oxygen- and vacancy-derived spin-singlet diamond color centers with metastable spin triplets: OV$^{2+}$ and VOV$^{2+}$

John Mark P. Martirez

The ST1 diamond color center was experimentally demonstrated to involve a substitutional oxygen atom (O$_C$) and carbon vacancy (V$_C$), has a spin singlet ground-state, and a metastable electron spin ancilla: a triplet. ST1's structure was left unsolved for more than a decade. With embedded multiconfigurational quantum mechanical theory, we investigate O$_C$-V$_C$-derived diamond defects, specifically both 0 and +2-charged coupled O$_C$V$_C$, and O$_C$ surrounded by V$_C$s along the [110] axis (V$_C$O$_C$V$_C$). We found both O$_C$V$_{C}^{2+}$ (C$_{3v}$) and V$_C$O$_C$V$_{C}^{2+}$ (C$_{2v}$) to have a spin-singlet ground state (1$^1$A$_1$) and metastable spin triplets. We demonstrate ST1 to be V$_C$O$_C$V$_{C}^{2+}$. The calculated vertical excitation energies of V$_C$O$_C$V$_{C}^{2+}$'s first (1$^1$B$_2$) and second (2$^1$A$_1$) bright spin-singlet excited states closely match ST1's experimental zero phonon line (2.2-2.3 eV). O$_C$V$_{C}^{2+}$ ($^1$E) absorbs much higher (2.8 eV). The two O lone pairs favor V$_C$O$_C$V$_C$ over O$_C$V$_C$, in a similar manner as the single N lone pair favors formation of N$_C$V$_C$ centers.
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Materials Science

The interplay between thermomigration and stress-driven hydrogen transport in metals

Daniel J. Long, Edmund Tarleton, Alan C.F. Cocks et al. (+1 more)

Thermomigration is the driving force for hydrogen transport due to a temperature gradient. It can compete with hydrogen transport induced by stress gradients. While stress-driven hydrogen migration is well established, thermomigration remains comparatively underexplored, largely due to limited mechanistic understanding and a scarcity of experimental data. In this work, we develop a thermodynamically consistent framework for hydrogen transport, incorporating a mechanistic model for thermomigration. This is implemented within a finite element framework using an effective chemical potential. Using case studies of iron and nickel heat exchangers and zirconium alloy nuclear fuel cladding, we quantify the competing and synergistic effects of thermomigration and stress-driven transport. We show that thermomigration often dominates hydrogen redistribution in heat-carrying components, even in the presence of significant thermal incompatibility stresses. However, stress-driven transport is shown to become decisive near sharp stress concentrators. A graphical method is introduced to rapidly identify the dominant transport mechanism without requiring fully coupled simulations. The results provide practical guidance for assessing hydrogen redistribution and embrittlement risk in heat-carrying structural components.
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All authors Daniel J. Long, Edmund Tarleton, Alan C.F. Cocks, Felix Hofmann

Materials Science · Cross-listed from physics.comp-ph

Physics-Informed Long-Range Coulomb Correction for Machine-learning Hamiltonians

Yang Zhong, Xiwen Li, Xingao Gong et al. (+1 more)

Machine-learning electronic Hamiltonians achieve orders-of-magnitude speedups over density-functional theory, yet current models omit long-range Coulomb interactions that govern physics in polar crystals and heterostructures. We derive closed-form long-range Hamiltonian matrix elements in a nonorthogonal atomic-orbital basis through variational decomposition of the electrostatic energy, deriving a variationally consistent mapping from the electron density matrix to effective atomic charges. We implement this framework in HamGNN-LR, a dual-channel architecture combining E(3)-equivariant message passing with reciprocal-space Ewald summation. Benchmarks demonstrate that physics-based long-range corrections are essential: purely data-driven attention mechanisms fail to capture macroscopic electrostatic potentials. Benchmarks on polar ZnO slabs, CdSe/ZnS heterostructures, and GaN/AlN superlattices show two- to threefold error reductions and robust transferability to systems far beyond training sizes, eliminating the characteristic staircase artifacts that plague short-range models in the presence of built-in electric fields.
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All authors Yang Zhong, Xiwen Li, Xingao Gong, Hongjun Xiang

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

Reply to "Comment on "Electric conductivity in graphene: Kubo model versus a nonlocal quantum field theory model"" (ArXiv:2506.10792v2)

Pablo Rodriguez-Lopez, Jian-Sheng Wang and Mauro Antezza

In the Comment by Bordag et al. [Phys. Rev. B 113, 207401 (2026) and ArXiv:2506.10792], concerns are raised regarding the validity of the results presented in [Phys. Rev. B 111, 115428 (2025)], where the theoretical descriptions of the electric conductivity of graphene obtained from the Kubo formula and from quantum field theory via the polarization tensor are compared. In this Reply, we show that these concerns arise from misinterpretations of Phys. Rev. B 111, 115428 (2025), in which the results are either inaccurately represented or applied outside the domain of validity of the model. We address the comments concerning the derivation of the Luttinger formula for the electric conductivity from the Kubo formula and clarify why the results of Phys. Rev. B 111, 115428 (2025) cannot be arbitrarily extended to make claims on the gauge invariance. We further demonstrate that our findings are fully consistent with the established and widely accepted literature cited in the Comment. We confirm that the model for electric conductivity discussed in Phys. Rev. B 111, 115428 (2025) correctly predicts a vanishing electric current in the absence of an external electric field, as physically required, and in contrast with the model advocated by the Authors of the Comment. We also show that the electric permittivity does not exhibit a double pole in $\omega$, contrary to the claim made in the Comment. Finally, we emphasize that the inclusion of losses is a standard and well-established approach in the study of transport properties of materials, including graphene, and we take the opportunity to correct a few minor typographical errors in Phys. Rev. B 111, 115428 (2025). We show and maintain that all results derived in Phys. Rev. B 111, 115428 (2025) are fully valid and correct.
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Materials Science

Physics-aware neural networks enable robust and full atomic structure determination via low-dose atomic electron tomography

Yao Zhang, Lanyi Cao, Zhen Sun et al. (+1 more)

Atomic electron tomography (AET) determines the three-dimensional (3D) coordinates and chemical identities of individual atoms from a series of scanning transmission electron microscopy images taken at different tilt angles. However, under the low dose conditions required to mitigate beam damage, the reduced signal-to-noise ratio forces a trade off among accuracy, robustness, and throughput, which ultimately limits the broader application of AET. Here, we introduce a physics aware, two stage neural networks (PANN) that incorporates physical constraints throughout its workflow to achieve accurate AET under low-dose imaging. First, a global local 3D ResUNet refines the initial reconstruction and corrects geometric distortions in the volume. Second, the local density around each identified atom is encoded using 3D Zernike moments. These feature descriptors, along with the atomic coordinates are then processed by a graph attention Transformer to classify the elemental species. We benchmark the PANN workflow using a dataset of 42,588 reconstructed volumes, covering diverse noise models, materials morphologies, and dose settings. Under low dose conditions, PANN significantly improves performance, reducing the atomic coordinates error and leading to an increase in the atomic recovery rate. The framework's performance on experimental lose dose AET data across nanoparticles of varying morphology and composition demonstrate robust generalization. We anticipate this approach will extend the applicability of AET, particularly in investigating materials sensitive to electron dose or chemical state, including halide perovskites, zeolite, and quantum dot.
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All authors Yao Zhang, Lanyi Cao, Zhen Sun, Jihan Zhou

Materials Science

DSC curve fingerprints directly encode mechanical properties of aluminum alloys

Lukas Pichlmann, Samuel Studer, Aurel R. Arnoldt et al. (+2 more)

Differential scanning calorimetry (DSC) is a standard tool for studying precipitation and phase transformations in aluminum alloys, yet its relation to mechanical performance has so far remained mostly indirect. Here, we demonstrate that DSC curves themselves act as fingerprints that directly encode mechanical properties. Four representative 6xxx series alloys (Al-Mg-Si) were subjected to different natural and artificial aging regimens, followed by DSC heat-flow measurements and tensile testing. Machine learning models trained on the thermograms predicted yield strength, ultimate tensile strength, and uniform elongation in five-fold grouped cross-validation, with the best model (Lasso) achieving R^2 values of 0.93, 0.86, and 0.87 and mean absolute errors of 14.3 MPa, 11.1 MPa, and 1.5 percent, respectively. Leave-one-alloy-out evaluation with sparse calibration using anchor samples further demonstrated generalization across alloy chemistries. While direct prediction on unseen alloy data degraded performance substantially, inclusion of as few as one to two anchor conditions from the target alloy recovered predictive accuracy, approaching that of the standard cross-validation. Feature importance analysis revealed that the 230 to 270 C region, associated with precipitation of the primary hardening phase beta”, contributed most strongly to predictive accuracy, providing direct mechanistic validation of the model. These findings establish DSC as a diagnostic tool that can serve as a rapid proxy for mechanical property evaluation, enabling accelerated alloy screening, process optimization, and integration of thermal analysis into data-driven manufacturing.
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All authors Lukas Pichlmann, Samuel Studer, Aurel R. Arnoldt, Paul Oberhauser, Johannes A. Österreicher

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

Theory of x-ray scattering from optically pumped excitons in atomically thin semiconductors

Joris Sturm, Andrei Benediktovitch, Nina Rohringer et al. (+1 more)

We propose a framework to explore the internal charge distribution of mesoscopic quasiparticles by inelastic x-ray scattering, while also accounting for the conventional scattering from electrons. Specifically, we investigate a new contribution of intrinsic and optically pumped excitons (bound electron-hole pairs) to the x-ray scattering spectrum of transition metal dichalcogenides (TMDCs). The optical excitation leads to the creation of Wannier exciton populations, adding new quasi-elastic processes beyond the conventional electronic features to the x-ray scattering spectra. Differential spectra (with and without optical pumping) can be used to isolate and identify the internal charge distribution of the optically pumped excitons in the scattering response, potentially offering insights into many-body interactions and quasi-particle dynamics in 2D systems.
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All authors Joris Sturm, Andrei Benediktovitch, Nina Rohringer, Andreas Knorr