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Physics Condensed Matter Materials Science

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Tuesday 26 May

Materials Science

Defect engineering of ultrathin gallium nitride via electric fields for advanced electronic, magnetic, and gas sensing applications

Yujia Tian, Devesh R. Kripalani, Ming Xue et al. (+1 more)

Scaling wide-band-gap semiconductors to the ultrathin limit offers a transformative pathway for power electronics, with gallium nitride (GaN) representing a cornerstone material in this class. However, the operational resilience and functional tunability of its two-dimensional form (g-GaN) remain underexplored. This work shifts the focus from idealized systems to the complex materials behavior under realistic conditions, investigating how the synergistic effects of point vacancy defects, strain, and external electric fields govern its electronic, magnetic, and sensing landscapes. We demonstrate that these factors are not merely perturbations but are fundamental to modulating the material response. Our first-principles calculations suggest g-GaN maintains electronic stability under intense electric fields; notably, gallium vacancies are predicted to further extend the theoretical stability limit. While in-plane tension preserves the band gap evolution under an electric field, in-plane compression facilitates low-field metallization. Using nitrogen monoxide (NO) adsorption as a prototype, we find that the interaction is defect-modulated and potentially tunable by electric fields. Analysis of adsorption energetics and diffusion barriers suggests the gallium vacancy may act as a thermodynamic trap for NO. Targeted hybrid-functional (HSE06) validation confirms the reliability of observed adsorption trends and theoretical metallization thresholds, while revealing that precise electronic-exchange treatment is critical for capturing the magnetic ground state of nitrogen vacancies. By systematically examining the geometry, energetics, band structure, density of states, magnetic response, and charge transfer, this study clarifies the interplay between defects and external electric fields, providing insights into theoretical upper bounds for property tuning and semiconductor device engineering.
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All authors Yujia Tian, Devesh R. Kripalani, Ming Xue, Kun Zhou

Materials Science

Tunable competing optical excitation pathways in the topological surface states of Bi$_2$Te$_3$

Shin Yokoyama, Takahito Takeda, Nagi Suzuki et al. (+9 more)

Understanding coherent optical responses of topological surface states (TSSs) requires disentangling excitation pathways from the electronic band structure. Here, using angle-resolved two-photon photoemission spectroscopy, we identify two distinct excitation pathways in the TSSs of Bi$_2$Te$_3$: an off-resonant transition via virtual states and a resonant transition via unoccupied intermediate states. A pronounced modulation of the spectral response is observed, revealing a competition between the two coherent pathways. This competition is tunable via temperature-induced shifts of the chemical potential, which selectively modify the resonant channel. These results provide microscopic insight into the optical excitation mechanisms of TSSs and highlight the potential for controlling their optical responses, relevant for future spintronic devices.
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All authors Shin Yokoyama, Takahito Takeda, Nagi Suzuki, Takuma Iwata, Ping Zhou, Yogendra Kumar, Akio Kimura, Koji Miyamoto, Taichi Okuda, Mario Novak, Uwe Bovensiepen, Kenta Kuroda

Materials Science

MatFormBench: A Benchmarking Evaluation Framework for Target-Driven Materials Formulation

Linhan Wu, Chenxi Wang, Chuhan Yang et al. (+2 more)

Inverse design of materials has significantly advanced target-driven formulation optimization, yet existing materials machine learning benchmarks remain limited to forward property prediction, failing to systematically evaluate inverse optimization and generation algorithms, a critical gap that hinders the progress of target-driven materials design. To address this limitation, we propose MatFormBench, a novel benchmarking ecosystem tailored to evaluate and guide generative strategies for target-driven formulation. MatFormBench integrates a physics-driven formulation generation scheme to generate synthetic samples that faithfully emulate realistic materials structure-property response relationships, complemented by five escalating difficulty levels to quantify the complexity of these relationships. To rigorously assess algorithm performance, we further propose MatFormScore, a multi-dimensional metric that comprehensively quantifies performance across five critical axes: target success, search efficiency, exploratory capacity, robustness, and stability. We validate MatFormBench by evaluating 39 diverse inverse design algorithms, covering classical surrogate-assisted black-box search, state-of-the-art deep generative models, and increasingly popular Large Language Model (LLM)-based recommendation strategies. Across 1170 standardized algorithm-task evaluations, diffusion-based models demonstrate the strongest overall performance, while Variational Autoencoder (VAE)-based and Genetic Algorithm (GA)-based methods exhibit distinct advantages in specific scenarios. By establishing a unified evaluation standard for target-driven materials formulation, MatFormBench enables reproducible benchmarking, principled algorithm comparison, and diagnostic analysis of inverse design strategies, providing a foundational tool for advancing materials inverse design.
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All authors Linhan Wu, Chenxi Wang, Chuhan Yang, Zhengwei Yang, Yuyang Liu

Materials Science

Visualizing Degradation in Anode-Free High-Utilization Aqueous Batteries Across Cell Lifetime

Sofia K. Catalina, Kyle Frohna, Willow Thompson et al. (+6 more)

Operando microscopy has unveiled key mechanistic insights in battery materials during early cycling, but long-term characterization to unveil material evolution, degradation, and failure remain limited. To address this gap, we develop a custom operando optical microscope that captures images across hundreds of cycles and hours using optically accessible, anode-free pouch cells. We image through-plane, bulk-representative electrodeposition behavior of aqueous tin metal anodes, which are promising due to their high energy density but whose reactivity limits practical cycle life. We show that substrate governs the morphology and stability of plated tin, particularly at high plated capacities. Specifically, copper substrates exhibit a multi-stage tin growth mode, which results in high overpotentials and irreversible active material loss at high plated capacities. In contrast, graphite substrates display a single-stage growth mode with slower kinetics. Using this insight, we balance performance and stability to demonstrate a high-utilization (70%, 630 mAh g$^{-1}_{Sn}$) porous graphite substrate Sn anode with high efficiency and long lifetime. Our results underscore the importance of material and device optimization guided by operando characterization across device lifetime with broad applicability to electrochemical systems.
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All authors Sofia K. Catalina, Kyle Frohna, Willow Thompson, Katherine J. Harmon, Dasol Yoon, Jianbo Wang, Colin Ophus, Daniel N. Congreve, William C. Chueh

Materials Science

Near-Infrared-Triggered Photodynamic Antibacterial Therapy Using Rose Bengal-Coated Upconverting Nanoparticles

Pratik Deshmukh, Nandini Ahuja, Bhumika Sharma et al. (+3 more)

Antimicrobial photodynamic therapy (aPDT) is a promising modality for inactivation of antibiotic resistant bacteria, relying on the activation of a photosensitizer (PS) by light of a specific wavelength. This process results in the formation of reactive oxygen species, which ultimately induce cell death. However, aPDT in its conventional form, is limited by the shallow penetration of visible light, restricting its effectiveness for treatment of soft tissue and orthopaedic tissues. To overcome this limitation, near-infrared (NIR) absorbing PS can be used. However, poor stability in vivo after injection, ineffective microbial targeting due to hydrophilic nature and off-site tissue damage are the issues with use of NIR absorbing bare PSs. This issue can be mitigated by combining NIR light with a upconverting nanoparticles (UCNPs), which mediate in conversion of NIR into visible light for effective PS activation. In this study, LaF$_3$:Er$^{3+}$,Yb$^{3+}$ nanoparticles were synthesized using a hydrothermal method and coated with Rose Bengal (RB), a promising hydrophilic PS for aPDT, to evaluate the potential for NIR-triggered aPDT. Characterization of the synthesized UCNPs confirmed the crystalline structure, size distribution and successful RB functionalization. Photophysical studies demonstrated efficient energy transfer between UCNPs and RB, leading to singlet oxygen ($^1$O$_2$) generation in vitro. Antibacterial studies against Methicilin resistant Staphylococcus aureus (MRSA), a superbug of implicated soft tissue and orthopaedic infections, revealed significant photo-bactericidal efficacy upon NIR irradiation, indicating the potential of RB-coated UCNPs for aPDT applications.
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All authors Pratik Deshmukh, Nandini Ahuja, Bhumika Sharma, Khageswar Sahu, Srinibas Satapathy, Shovan Kumar Majumder

Materials Science

Conditions for domain-free negative capacitance

Prasanna Venkatesan Ravindran, Priyankka Gundlapudi Ravikumar and Asif Islam Khan

While negative capacitance has been demonstrated in ferroelectric-dielectric heterostructures in the form of capacitance enhancement, all experimental evidence, to date, suggests the existence of domains therein. Here, we address the question: what are the conditions to achieve ideal, domain-free negative capacitance in ferroelectric-dielectric heterostructures? Our main claim is that for given thicknesses of the ferroelectric and the dielectric layers, there is a critical value of domain wall energy parameter – above which the system would be stabilized in an ideal and robust domain-free negative capacitance state and would be robust against domain formation. Our analyses suggest that to achieve ideal negative capacitance, efforts should lie in understanding the means to control the domain wall energy on all fronts, both theory and experiments via high throughput design, discovery, and engineering of ferroelectrics.
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Materials Science · Cross-listed from cond-mat.mes-hall

Anharmonic Quantum Transport Analysis of Thermal Transport Anomalies in Ultrathin Silicon Nanowires

Lokanath Patra, Mayur Pratap Singh and Satish Kumar

Thermal transport in low-dimensional semiconductors is important for nanoelectronics, quantum devices, and thermoelectrics. Recent molecular dynamics (MD) studies reveal a nonmonotonic diameter dependence of thermal conductivity in ultrathin silicon nanowires (NWs), but classical MD is limited at low temperatures and under strong confinement. Here, we investigate this anomaly using anharmonic non-equilibrium Green's function (NEGF) simulations combined with density functional theory-trained neuroevolution potentials. All transport results are expressed as effective thermal conductivities ($\kappa_{\mathrm{eff}}$) for NW devices with a finite channel length of $L=10$ nm. At 300 K, $\kappa_{\mathrm{eff}}$ decreases with diameter to minima at 6.24 and 5.50 nm for [001]- and [110]-oriented NWs, respectively. At 10 K, the corresponding minima occur at 7.33 and 5.50 nm. At room temperature, dominant momentum-conserving normal scattering relative to Umklapp processes enables Poiseuille-like hydrodynamic phonon flow that competes with boundary scattering. At cryogenic temperatures, Bose–Einstein statistics restrict heat transport to low-frequency confined acoustic-like modes. Comparison with the harmonic Landauer limit reveals a finite correction to $\kappa_{\mathrm{eff}}$ from anharmonic phonon–phonon scattering. Classical MD neglects quantum suppression and overexcites high-frequency vibrations, leading to overestimated thermal conductivity in thinner, strongly confined NWs at low temperatures. The NEGF framework incorporates quantum statistics and anharmonic scattering, providing a quantum-mechanical description of thermal transport down to 10 K.
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Materials Science

Modulation of charge density waves in a twisted vortex moire superlattice

Qian Fang, Yanhao Shi, Jingyi Duan et al. (+11 more)

Twisted moire superlattices in van-der-Waals heterostructures provide a powerful platform for engineering correlated states through moire-band reconstruction. However, whether globally coherent electronic orders can be continuously manipulated at the nanoscale remains largely unexplored. Reconstructed moire structures in small-angle and near-commensurate regime feature continuously varying local environments, offering new opportunities for nanoscale manipulation of correlated phases. Here, we report the modulation of charge density wave (CDW) states in a twisted vortex moire superlattice formed between monolayer VTe2 and superconducting NbSe2. Scanning tunneling microscopy/spectroscopy reveals that the intrinsic long-range CDW of monolayer VTe2 is reconstructed into inequivalent local phases with distinct stability and coherence within a single moire unit cell, including suppressed CDW order and enhanced short-range CDW correlations persisting to room temperature. First-principles calculations show that the reconstructed CDW landscape originates from strong local strain variation, where compressive strain substantially stabilizes the charge order. Furthermore, the modulated CDW states exhibit competing interplay with proximity-induced superconductivity. Our results establish vortex moire superlattices as a versatile platform for nanoscale manipulation of correlated electronic orders in low-dimensional quantum materials.
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All authors Qian Fang, Yanhao Shi, Jingyi Duan, Hui Guo, Yikai Chen, Senhao Lv, Jiayi Wang, Zhongyi Cao, Jiayi Huang, Siyu Xu, Haitao Yang, Wei Jiang, Hui Chen, Hong-Jun Gao

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

Selective Biexciton Generation Under Energy-Time Entangled Quantum Light in Quantum Dots

Kaiyue Peng, Chieh Tsao, Hendrik Utzat et al. (+1 more)

Quantum light provides opportunities for controlling multiphoton absorption beyond classical limits. Here, we investigate biexciton generation in nanocrystal quantum dots driven by energy-time-entangled photon pairs generated via spontaneous parametric down-conversion. We show that frequency-time correlations between pairs of photons increase the population of biexcitons over excitons, thereby lending specificity to the excitation of many-body states. By employing a three-level model, we demonstrate that biexciton generation depends nontrivially on the photon entanglement time and the pump bandwidth. We find that maximizing efficiency requires an optimally shaped entangled photon field rather than simply scaling parameters for a monotonic improvement. Extending to a realistic CdSe/CdS core-shell quantum dot containing many excitonic states coupled to the quantum field, we demonstrate that increasing the bi-photon arrival-time entanglement (closer arrival time) enhances constructive pathway interference and expands accessible excitation channels while preserving better energy-conservation excitation than classical light when generating biexcitons. Furthermore, tuning the time correlation properties enables selective excitation of closely spaced biexciton states. These results establish entangled photons as a tool for selective excitation and control of higher-order excited states in quantum-confined systems.
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All authors Kaiyue Peng, Chieh Tsao, Hendrik Utzat, Eran Rabani

Materials Science

Structural Alter-Phononics: Sublattice-Momentum Locking in Spinless Lattice Dynamics

Jing-Yang You, Zhen Zhang, Xianlei Sheng et al. (+1 more)

The discovery of altermagnetism has shown that crystal symmetry can generate momentum-dependent internal polarization without net magnetization. Whether an analogous form of symmetry-organized momentum-space order can exist for spinless lattice vibrations remains unresolved. Here we identify a structural mechanism for $alter$-$phononics$, in which phonon eigenmodes formed from structurally equivalent sublattices acquire momentum-dependent sublattice polarization and frequency splitting in nonmagnetic crystals. The central quantity is the sublattice-resolved dynamical asymmetry $\Delta(\mathbf q)=D_{AA}(\mathbf q)-D_{BB}(\mathbf q)$, which controls the associated eigenvector polarization. We show that this effect requires an alter-generator that maps equivalent sublattices onto one another while rotating the wave vector, together with the absence of inversion exchange and little-group sublattice-exchange constraints that would otherwise enforce sublattice equipartition. These symmetry rules generate nematic $d$-wave, tetragonal $d/g$-wave, and tripartite six-lobe phonon textures. First-principles calculations demonstrate the mechanism in representative nonmagnetic crystals and show how a symmetry-preserving structural distortion can unlock a hidden $d_{x^2-y^2}$-type texture by removing glide-induced equipartition traps while retaining the screw-axis alter-generator. We further show that the eigenvector texture is inherited by sublattice-projected electron-phonon coupling and anharmonic response functions. Our results establish structural alter-phononics as a spinless counterpart to altermagnetic momentum-space order and provide experimentally testable signatures in finite-$\mathbf q$ phonon spectra and displacement patterns.
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All authors Jing-Yang You, Zhen Zhang, Xianlei Sheng, Gang Su

Materials Science

Reduced-order topology optimization of defect spectra in phononic crystals

Xinlin Xu and Junji Kato

Defect modes localize vibrations within phononic-crystal bandgaps. Prescribing their frequencies alone does not ensure separation from competing modes. We use frequency-dependent selection weights to combine attraction of target-adjacent modes with repulsion of competing in-gap modes. Only the central defect cell is optimized within a previously designed, fixed host bandgap. Cell-level Craig–Bampton reduction retains physical interface coordinates, allowing the host contribution to be assembled once while the defect basis and matrices are updated. Across three numerical cases, the reduced-order method accelerates defect optimization by approximately 13–20 times. A comparison with attraction-only optimization shows that the combined objective moves competing modes away from the target and increases the minimum target-to-non-target frequency separation. Full-order reanalysis shows that the optimized modes remain close to the prescribed frequencies and localized around the defect. A finite-array calculation shows enhanced response near the target relative to the defect-free host under the prescribed loading.
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Monday 25 May

Materials Science

Atomic Structure of Amorphous Optical Coatings of TiO$_2$-doped GeO$_2$ by Grazing-Incidence Total X-ray Scattering Measurements

K. Prasai, J. Jiang, K. Lee et al. (+13 more)

Reducing coating thermal noise in future gravitational-wave detectors requires identifying the atomic motifs that control mechanical loss in amorphous optical coatings. We combine grazing-incidence X-ray pair distribution function measurements with atomic-structure modeling to study amorphous TiO$_2$-doped GeO$_2$ films over Ti cation concentrations from $\sim$11 % to $\sim$48 %, before and after annealing. The structural analysis reveals systematic composition- and annealing-dependent changes in short- and intermediate-range order. Increasing Ti content raises the average Ti coordination and promotes edge- and face-sharing polyhedral connections, while Ge remains predominantly fourfold coordinated. Annealing reduces these compact shared-polyhedron motifs and sharpens the first sharp diffraction peak, indicating a more relaxed intermediate-range network. Among the structural descriptors examined, the clearest correlation with the annealing-induced reduction in mechanical loss is the decrease in edge- and face-sharing polyhedra. These results connect composition, annealing, atomic structure, and mechanical dissipation in TiO$_2$-doped GeO$_2$, providing microscopic guidance for optimizing low-noise mirror coatings.
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All authors K. Prasai, J. Jiang, K. Lee, L. Yang, M. Chicoine, S. Khadka, A. Markosyan, A. Mehta, C. S. Menoni, S. Patel, F. Schiettekatte, B. Shyam, G. Vajente, H-P Cheng, M. M. Fejer, R. Bassiri

Materials Science

High-temperature instability of artificial cuprorivaite: a study using thermal analysis, X-ray powder diffractometry and polarized light microscopy

Vladimir A. Yuryev, Sergey V. Kuznetsov, Alexander A. Alexandrov et al. (+1 more)

CaCuSi$_4$O$_{10}$ powder was studied by differential scanning calorimetry and thermogravimetry methods in the range from room temperature to 1450$\,^{\circ}$C at heating and cooling rates of 20$\,^{\circ}$C/min. The process of decomposition of cuprorivaite, the composition and transformations of its decomposition products during successive heat treatments were also studied by powder X-ray diffraction and polarization optical microscopy techniques. It was found that CaCuSi$_4$O$_{10}$ starts to decompose by incongruent melting at a temperature of about 1020$\,^{\circ}$C, with the minimum of the endothermic DSC peak associated with this process being at 1064.4$\,^{\circ}$C. CaCuSi$_4$O$_{10}$ decomposes irreversibly and subsequent cyclic annealings up to a temperature of 1450$\,^{\circ}$C at heating and cooling rates of 20$\,^{\circ}$C/min do not cause its re-synthesis. CaCuSi$_4$O$_{10}$ transforms into a two-phase system consisting of acicular crystals of monoclinic tridymite fused with green glass with the composition CuO$\,-\,$Cu$_2$O$\,-\,$CaO$\,-\,$SiO$_2$, with the weight ratio of tridymite to glass being about $12:13$, as a result of two successive annealings up to the temperature of 1450$\,^{\circ}$C.
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All authors Vladimir A. Yuryev, Sergey V. Kuznetsov, Alexander A. Alexandrov, Tatyana V. Yuryeva

Materials Science

Finite Temperature Stacking Fault Stability in Random and Locally Ordered CoCrNi beyond the Harmonic Approximation

Reza Namakian, Fei Shuang, Thomas D Swinburne et al. (+3 more)

Previous density functional theory (DFT) calculations for random solid solution (RSS) CoCrNi predict negative intrinsic stacking-fault energy (ISFE) at 0 K, contrary to experimental observations of finite stacking-fault widths. Two explanations have been proposed: finite-temperature stabilization of the RSS state, suggested by harmonic approximations showing increasing ISFE with temperature, and local chemical order (LCO), which shifts the ISFE to positive values at 0 K. Here, we compute temperature-dependent generalized stacking-fault free energies for RSS and LCO CoCrNi using a near-quantum-accuracy machine learning interatomic potential and the fully anharmonic projected average force integrator. Unlike harmonic approximations, our anharmonic calculations show that the RSS ISFE decreases with temperature and remains negative, indicating that RSS stacking faults are not thermally stabilized at elevated temperatures. By contrast, LCO maintains positive ISFE over 0-1000 K. Molecular dynamics simulations further confirm unbounded dislocation dissociation in RSS CoCrNi but finite stacking-fault widths in the LCO state.
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All authors Reza Namakian, Fei Shuang, Thomas D Swinburne, Poulumi Dey, Ali Erdemir, Wei Gao

Materials Science

Resilience of the physicochemical properties of graphene-based materials for applications in harsh radiation environments

Marcilei A. Guazzelli, Saulo G. Alberton, Nemitala Added et al. (+16 more)

The development of radiation-tolerant materials capable of maintaining structural, electrical, and thermal stability in extreme, radiation-rich environments remains a critical challenge in materials science. In this work, the effects of 60 MeV 35Cl ion irradiation on highly oriented pyrolytic graphite (HOPG) and multilayer reduced graphene oxide (ML-rGO) were investigated. The samples were exposed to fluences of 5.11 x 10^9 and 1.3 x 10^10 ions/cm^2 and characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and electrical transport measurements. The results show that the irradiation response is strongly influenced by the initial structural organization of the material. In HOPG, ion exposure leads to a progressive loss of crystalline order, evidenced by XRD peak broadening and an increase in the Raman ID/IG ratio, accompanied by a reduction in electrical transport performance. In contrast, ML-rGO exhibits distinct behavior at higher fluences, suggesting partial structural reorganization. The appearance of more defined graphitic features in XRD and Raman analyses, along with changes in surface morphology and electrical response, suggests the formation of more ordered sp2 domains. These findings indicate that irradiation effects vary with the initial degree of order, providing useful insights for selecting carbon-based materials for devices operating under severe radiation conditions.
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All authors Marcilei A. Guazzelli, Saulo G. Alberton, Nemitala Added, Vitor A. P. Aguiar, Koiti Araki, Luis H. Avanzi, Francesco Cappuzzello, Manuela Cavallaro, Eliane F. Chinaglia, Marcia T. Escote, Fabio F. Ferreira, Mauro Giovannini, Renato F. Jardim, Sueli H. Masunaga, Nilberto H. Medina, Marcelo Nakamura, José R. B. Oliveira, Roberto B. B. Santos, Alexis C. Villas-Bôas

Materials Science

Diamond compound refractive lenses for high energy Dark Field X-ray Microscopy

Steffen Staeck, Can Yildirim, Frank Seiboth et al. (+4 more)

Compound-refractive lenses (CRL) are a type of x-ray optics that find widespread applications as focusing and imaging lenses. The choice of material is one of the most defining properties of these lenses. In this work, we present a CRL made out of diamond. It provides an advantageous balance between refractivity and absorption, along with good manufacturability. Compared to Be CRLs, it features a higher optical density and thus enables application at higher photon energies without relying on large lens stacks or very small radii of curvature, which are challenging to manufacture. A diamond CRL is characterized for use as an objective for Dark-field X-ray Microscopy (DFXM) at the ID03 beamline of the European Synchrotron Radiation Facility (ESRF) and compared to Al and Be CRLs at 17 keV, 33 keV and 37 keV. Increasing the photon energy in DFXM from 17 keV to 37 keV opens up the possibility to investigate new sample systems, that were previously opaque to low energy x-ray radiation. The capability of the diamond CRL at 33 keV is illustrated through DFXM measurements on two 0.5 mm-thick iron-based samples, which cannot be probed at 17 keV.
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All authors Steffen Staeck, Can Yildirim, Frank Seiboth, Terence Manning, Thomas Roth, Jean-Charles Stinville, Carsten Detlefs

Materials Science

AutoDFT: A Closed-Loop Multi-Agent Framework for Autonomous DFT Calculations

Penghui Yang, Zhonghan Zhang, Yue Li et al. (+6 more)

Density functional theory (DFT) serves as the basis for computational discovery in materials science and chemistry, yet each calculation demands extensive human effort: adjusting algorithms when convergence stalls, revising plans when unexpected physics emerges, and inserting steps as intermediate results reshape the problem. Existing LLM-based agents automate only the initial planning stage, producing a full execution plan upfront and leaving all subsequent adaptation to hand-crafted rules. As a result, these workflows remain fragile, do not generalize well beyond pre-planned scenarios, and often require expert intervention when failures or unexpected intermediate results require changes to the calculation path. Here, we introduce AutoDFT, a closed-loop multi-agent framework that embeds LLM reasoning into every stage of the DFT lifecycle, where a strategic planner produces a skeletal plan of step objectives; a step planner generates numerical parameters just in time from preceding results; and a monitor-recover-reflect cycle diagnoses failures, repairs them, and revises the plan when the evidence justifies it. We demonstrate both breadth and depth: breadth on VASPBench, a purpose-built benchmark spanning 34 tasks and 9 DFT calculation types, where AutoDFT achieves 94.1% task-level success with GPT-5.2; and depth on established materials databases, where AutoDFT produces quantitatively reliable property predictions across electronic, magnetic, and energetic properties. By closing the loop between planning and execution, AutoDFT enables experimentalists without deep computational expertise to obtain reliable first-principles results.
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All authors Penghui Yang, Zhonghan Zhang, Yue Li, Xinrun Wang, Yanchen Deng, Yuhao Lu, Bijun Tang, Zheng Liu, Bo An

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

Characterizing emergent multiscale dynamics in colloidal nanoparticle gels

William D. Brackett, Zachary M. Sherman, Felix Lehmkühler et al. (+2 more)

Colloidal gels assembled from nanoparticles (NPs) are a versatile class of soft network-based materials capable of rich dynamic, mechanical, and even optical or magnetic responses to stimuli. Understanding how their hierarchically organized processes relate to macroscopic network properties remains a broad and unresolved problem in soft matter physics. The mechanisms of gel formation can depend sensitively on the pathway and the nature of NP interactions, thus far preventing a unified theoretical bridge between nanoscopic interactions and structural evolution and network dynamics. Indirect measurement of dynamics using light-scattering techniques provides an experimental means to quantify underlying particle and network motion. X-ray photon correlation spectroscopy (XPCS) has emerged as a powerful tool for probing nanoscopic motion in nanoparticle gels, but alone cannot resolve the full spatiotemporal spectrum of dynamics that drive gelation, aging, and network mechanical properties. While in situ rheo-XPCS enables simultaneous probing of nanoscale and bulk mechanical responses, complementary light scattering, microscopy, or simulations can extend spatiotemporal characterization and, consequently, understanding of NP gel network physics. Implementing a modular model platform with tunable primary nanoparticle features allows systematic variation of nanoscopic characteristics that drive emergent gel responses and inform the development of theoretical models for a wide range of soft, dynamic, nanostructured materials. The rapid expansion of XPCS capabilities at fourth-generation light sources, combined with complementary tools and robust model systems, positions the field to move beyond descriptive fundamental studies toward the design of nanoparticle gels with adaptive and programmable behaviors.
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All authors William D. Brackett, Zachary M. Sherman, Felix Lehmkühler, Thomas M. Truskett, Delia J. Milliron

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

Observation of the Optical Phonons in {\alpha}-MnTe films

Himanshu Sheokand, Arun K Kumay, Mazharul Islam Mondal et al. (+6 more)

The altermagnetic materials have emerged as model systems for studying spin split electronic structures, yet controlled epitaxial growth on technologically relevant substrates remains challenging. Among the known candidates, MnTe stands out as a prominent altermagnetic material owing to its layered structure and high Neel temperature. Here, we report the molecular beam epitaxy (MBE) growth of high quality alpha MnTe thin films on GaAs(111)B substrates and provide a comprehensive analysis of the growth evolution and structural properties. Raman spectroscopy reveals multiple vibrational features of alpha MnTe including modes near 121, and 140 1/cm. Combined with first principles phonon calculations, these features are identified as the Raman-active phonons of the hexagonal NiAs type lattice. Our results show that the high crystalline quality of MBE grown alpha MnTe enables the complete experimental resolution of all symmetry allowed Raman active phonon modes, highlighting epitaxial alpha MnTe as a robust thin film platform for investigating altermagnetism and its lattice coupled excitations.
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All authors Himanshu Sheokand, Arun K Kumay, Mazharul Islam Mondal, Milo Sprague, Ravinder Sharma, Jayan Thomas, Dariusz Kaczorowski, Andrzej Ptok, Madhab Neupane

Materials Science

Magneto-optic phonon resonances in magnetic topological EuCd2As2 via helical Raman spectroscopy

Jin Ho Kang, Liangbo Liang, Ioannis Petrides et al. (+6 more)

EuCd2As2 materials have two magnetic ordering states: antiferromagnetic (AFM) and ferromagnetic (FM) when their chemical tunability is utilized. While AFM-EuCd2As2 has a nonzero magnetoelectric response due to its symmetry breaking with spin configuration, FM-EuCd2As2 is an ideal candidate for studies of Weyl physics because of its minimum number of Weyl points with opposite chirality. In this article, we examine cryogenic low-frequency Raman spectroscopy of phonon modes in FM-EuCd2As2 crystals using circular polarization configurations, with support from density functional theory calculations, and investigate in-plane magneto-anisotropy by linear polarization configuration below the Curie temperature (Tc = 26 K). We attribute the anomalous enhancements in Raman intensities below the Curie temperature are due to spin-phonon coupling. Furthermore, we see that A-mode peaks can be distinguished by magneto-helical Raman spectroscopy through the magneto-optic effect and that the degree of circular polarization (DCP) of 12.5 meV peak reaches 60% at 4.2 K and becomes saturated. We also examine AFM-EuCd2As2 below Néel temperature (TN = 9 K) to compare with FM-EuCd2As2, but we hardly observe spin-phonon coupling and find negligible DCP values due to almost zero net magnetization. Our results contribute to the understanding of the phonon dynamics and the interplay between topology and magnetism in FM-EuCd2As2, through helical light and external magnetic fields. This lays the foundation for utilizing state-of-the-art Weyl systems for applications in thermoelectrics, phononic devices, and topological quantum computing.
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All authors Jin Ho Kang, Liangbo Liang, Ioannis Petrides, Subhajit Roychowdhury, Kai-Chi Chang, Chandra Shekhar, Claudia Felser, Prineha Narang, Chee Wei Wong

Materials Science

Theory of Electrically Detected Magnetic Resonance of Silicon Vacancy-Related Spin Pairs in Silicon Carbide

David A. Fehr, Corey J. Cochrane, Stephen R. McMillan et al. (+3 more)

We present a quantitative theory for simulating the electrically detected magnetic resonance (EDMR) of silicon vacancy-related spin pairs in silicon carbide using steady-state Lindblad master equations. In our theory, we consider V1a and V2a deep level silicon vacancies near the (0/-) charge state transition level in proximity to a previously identified nitrogen-related complex, the incomplete K-center, due to the hyperfine, spin structure, and Landé g factor of the shallow state. Our theory describes recent room temperature measurements attributed to V1a silicon vacancies, with reasonable extracted parameters for defect spin coherence times and electrical transport rates. At lower temperatures we predict that the shallow level hyperfine structure may be spectrally resolvable. Finally, we predict the EDMR spectrum of V2a silicon vacancy-related spin pairs and predict that two-photon, double quantum transitions of the silicon vacancy's negative charge state can be electrically read-out for enhanced magnetic field sensing.
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All authors David A. Fehr, Corey J. Cochrane, Stephen R. McMillan, Nicholas J. Harmon, Patrick M. Lenahan, Michael E. Flatté

Materials Science

Nuclear-Electron Hyperfine Coupling of the Shallow States Associated with Vacancies in Gallium Nitride

Joseph Sink and Michael E. Flatté

We use multiband real space Green's functions computed using open-boundary conditions for clean GaN to exactly solve the potential-scattering Dyson equation to obtain the electronic structure of single nitrogen and gallium vacancies. From these vacancy solutions, we compute the local density of states as well as the Fermi contact and anisotropic contributions to the hyperfine field in the vicinity of the defect. These quantities directly affect electrically-detected magnetic resonance signals, which can be used to identify these defects when present in GaN devices.
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Materials Science · Cross-listed from cond-mat.str-el

Magnetic ground state of a prototype quasicrystal approximant: a candidate for octahedral spin ice physics

Leonie Woodland, Farid Labib, Dmitry Khalyavin et al. (+4 more)

Magnetic ordering in quasicrystals has recently emerged as a fertile ground for discovering unconventional magnetic states beyond the framework of periodic crystals. However, elucidating the microscopic origin of such states remains challenging due to the intrinsic aperiodicity of quasicrystals. Here, we address this issue by investigating the prototypical Tsai-type quasicrystal approximant Cd6Tb, which preserves the essential local geometry and connectivity of icosahedral quasicrystals while allowing detailed structural and magnetic characterization due to its translational periodicity. Using neutron diffraction measurements, we find a noncoplanar multi-k magnetic ground state composed of Ising-like Tb moments arranged on a network of corner-sharing octahedra, the ingredients required to host octahedral spin-ice physics. Remarkably, only one third of the Tb moments develop long-range magnetic order, whereas the remaining moments display strongly reduced static order accompanied by persistent spin dynamics on microsecond timescales, as evidenced by muon spin rotation. This coexistence of ordered and fluctuating moments constitutes a potential realization of magnetic fragmentation - a key prediction of octahedral spin-ice physics - in a quasicrystal-related material.
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All authors Leonie Woodland, Farid Labib, Dmitry Khalyavin, Pascal Manuel, Fabio Orlandi, Hubertus Luetkens, Ryuji Tamura

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

Uncovering multi-channel magnetic hopfion annihilation via a single-node, billion-spin-scale atomistic framework

Qichen Xu and Anna Delin

Modern atomistic spin simulations combine long stochastic trajectories, thermodynamic sampling, static optimization and multi-image transition-path workflows, all of which rely on repeated evaluation of spin Hamiltonians and become computationally prohibitive on the large lattices required for three-dimensional magnetic textures. We introduce SpinX, a GPU-native atomistic spin simulation framework built around a unified Hamiltonian interface and multiple user-selectable computational backends. Its core is a crystallographic sublattice decomposition that reformulates translationally invariant spin interactions as multi-channel tensor convolutions, enabling dense, sparse and FFT-based convolution backends, while irregular systems are handled by pair-list evaluation and long-range dipolar fields by reciprocal-space FFT. Implemented in JAX, SpinX supports deterministic and stochastic Landau-Lifshitz-Gilbert dynamics, Monte Carlo sampling, static optimization, dynamical spectroscopy and string and geodesic nudged elastic band transition-path calculations on heterogeneous accelerator platforms. A validated mixed-precision mode combines fp32 field evaluation with fp64 spin-state propagation. We validate SpinX against analytical single-spin dynamics, finite-size thermodynamics of bcc Fe and transverse dynamic structure factors. Performance benchmarks show peak throughput exceeding 10 billion spin-site operations per second on a single accelerator and aggregate single-node workloads of over 1 billion atomic spins. Applying this framework to an exchange-stabilized magnetic hopfion, we uncover two competing annihilation channels on a million-spin atomistic lattice: a previously reported axial-collapse pathway and a distinct lateral-rupture pathway with a different transition morphology and activation barrier.(Due to arXiv's limit, the abstract shown here is a shortened version)
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Materials Science

Light-Induced Transient Polarization Reversal in Rhombohedrally Stacked Bilayer Transition Metal Dichalcogenides via an Electronic Mechanism

Xiangzhou Zhu, Stefano Mocatti and Matteo Calandra

Light-induced sliding ferroelectricity in two-dimensional van der Waals materials enables polarization control via relative layer motion. However, polarization switching occurs on the time scale of shear modes (tens of ps) and requires very large fluences, potentially damaging the samples. Here, using constrained density functional theory and many-body real-time simulations, we demonstrate an ultrafast electronic reversal of the total out-of-plane polarization sign in the photoexcited state, without requiring interlayer sliding, in rhombohedrally stacked transition-metal dichalcogenide bilayers. The polarization changes sign relative to its initial ground-state value at moderate fluences and within $\sim$ 200 fs, about 50 times faster than the typical shear-mode period. The ultrafast switching is driven by a rearrangement of localized dipoles around the tungsten sites. We establish a novel general mechanism for electronic control of low-dimensional ferroelectrics common to all polar multilayers having type II band alignment. Our work has direct implications for ultrahigh-speed volatile optical memory operating on sub-ps time scales.
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Materials Science

Berry Curvature Driven Transport in Silicon-Compatible Altermagnetic $\alpha$-MnTe Thin Films

Rajib Sarkar, Subhransu Kumar Negi, Arindom Das et al. (+10 more)

Integrating spin-dependent functionality with mainstream semiconductor technology is a central goal of modern spintronics, yet most candidate materials remain incompatible with silicon-based platforms. Here, we report the direct epitaxial integration of $\alpha$-MnTe thin films on Si(111) via molecular beam epitaxy and demonstrate a robust anomalous Hall effect (AHE) in this silicon-compatible altermagnetic system. Despite the absence of net bulk magnetization, the films exhibit a pronounced hysteretic Hall response, providing transport evidence consistent with finite Berry curvature generated by symmetry breaking in the thin-film geometry. High-resolution structural and spectroscopic characterization confirms phase-pure, epitaxial growth with hexagonal NiAs-type symmetry, while magnetotransport measurements reveal correlated hysteresis in both transverse and longitudinal channels with systematic temperature evolution. First-principles calculations reveal substantial uncompensated Berry curvature arising from the spin-split band structure, consistent with altermagnetic symmetry and the origin of the observed Hall response. These results establish MnTe/Si(111) as a silicon-compatible altermagnetic platform and chart a concrete pathway for embedding Berry-phase-driven functionalities into scalable semiconductor device architectures.
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All authors Rajib Sarkar, Subhransu Kumar Negi, Arindom Das, Arijit Mandal, Pankaj Bhardwaj, Sohini Guin, Aryaman Das, Naresh Shyaga, Kartick Biswas, Pavan Nukala, Laxmipriya Nanda, B. R. K. Nanda, Dhavala Suri

Materials Science · Cross-listed from cond-mat.supr-con

Substitution modulated transition from semimetal to superconductor in ZrTe$_{2-x}$Se$_x$ with coexistence of nontrivial electronic topology

V. M. Fim, C. F. Schuch, L. R. de Faria et al. (+5 more)

This study explores the emergence of superconductivity in high-quality ZrTe$_{2-x}$Se$_x$ crystals, grown via the isothermal chemical vapor transport (ICVT) technique. Resistive, structural, and thermal measurements reveal that substituting Te with Se in the ZrTe$_2$ matrix induces a superconducting state at low temperatures. The critical temperature ($T_c$) exhibits a clear dependence on the selenium concentration, peaking at $x=0.15$ with a $T_c$ of $4.8$ K. Calorimetric data indicates that even a low Se substitution range is capable of modifying both the electronic contribution and the vibrational modes of the crystal lattice. Combined with ab initio calculations and Wannier Hamiltonian interpolation between ZrTe$_2$/ZrSe$_2$, we established an extensive phase diagram mapping the transition from charge density wave (CDW) to the state with coexistence between the Dirac semimetal and superconductivity (SC), up to the semiconductor phase. This coexistence suggests that ZrTe$_{1.85}$Se$_{0.15}$ could be a candidate platform for topological superconductivity, as it hosts a nontrivial $\mathbb Z_2$ invariant, with nonvanishing surface states in its $(001)$ planes.
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All authors V. M. Fim, C. F. Schuch, L. R. de Faria, F. A. Santos, M. S. da Luz, S. S. Tsirkin, L. T. F. Eleno, A. J. S. Machado

Materials Science

Benchmarking Transparent Conductors

Amit Cohen and Lior Kornblum

Transparent conducting oxides (TCOs) are central to optoelectronic technologies, yet their design is often guided by popular figures of merit that are disconnected from the electrical requirement of actual devices. As a result, widely used metrics guide material design under conditions that can be impractical for devices. Here, we introduce a benchmarking framework to guide TCO development, in which transparent conductors are evaluated at fixed, application-relevant sheet resistance $(R_S)$. The resulting metric, $T_{app}(R_S)$, anchors comparison to device requirements, asking instead: What optical transparency can be obtained at the sheet resistance required by a given application? This approach provides a directly interpretable measure of performance, enabling materials to be benchmarked in terms of absolute transparency gains at a specified $R_S$. Applied to representative conventional and emerging TCOs, the framework defines the sheet-resistance landscape relevant to each application and maps how different materials perform within it. In doing so, it provides an application-rooted guide to material development and selection. More broadly, this approach establishes a general strategy for evaluating materials under fixed operational constraints, bridging the gap between materials design and device integration.
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Materials Science · Cross-listed from cond-mat.supr-con

Superconductivity and electronic structure evolution in the enforced semimetal Fe-doped ZrTe$_2$

L. M. Ishikura, C. F. Schuch, A. Faé Rabello et al. (+6 more)

ZrTe$_2$ is an outstanding layered semimetal due to the topologically nontrivial electronic structure. In this work, we present an investigation of the electronic evolution of ZrTe$_2$ in the presence of Fe intercalation, namely Fe$_{x}$ZrTe$_2$ ($x= 0 - 0.25$), scrutinized by both experimental measurements and ab initio calculations. While the first reveals a superconducting state with a maximum critical temperature $T_c = 2.74$ K ($x=$ 0.03), the latter indicates that the topological features of the pristine ZrTe$_2$ is sensitive to the distance between Te atoms and Zr layers. Also, the intercalation of Fe does not modify the non-trivial electronic band structure unlike the band crossings are now shifted slightly below $E_{F}$. In particular, a van Hove singularity near the Fermi level for a Fe content of $x=0.125$ is observed in the density of states, indicating that the superconducting order may be associated with features of the unfolded band structure and the concomitant enhancement of the density of states at $E_F$. Finally, our results reveal that the new compound with inclusion of Fe intercalation preserves the enforced semimetal classification.
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All authors L. M. Ishikura, C. F. Schuch, A. Faé Rabello, F. F. Nogueira, L. E. Corrêa, L. R. de Faria, J. Larrea Jiménez, L. T. F. Eleno, A. J. S. Machado

Materials Science · Cross-listed from cs.LG

UNATE: UNsupervised ATomic Embedding for crystal structures property prediction

Laura Solà-Garcia, Àlex Solé and Javier Ruiz-Hidalgo

Accurately predicting crystal properties is critical for accelerating materials discovery, but it is often limited by scarce labeled data and costly theoretical calculations. To alleviate this, we propose UNATE (Unsupervised Atomic Embedding), a framework that leverages structural information extracted from unlabeled crystal structures. UNATE integrates an unsupervised denoising autoencoder with self-supervised contrastive learning to learn robust atomic representations, which are then used as input features for downstream property prediction. Experimental results show that replacing raw atomic numbers with UNATE-pretrained node embeddings yields a 2.7% improvement over the full-data baseline. Notably, the benefits become more pronounced in scenarios with limited labeled data, reaching improvements of up to 10% when only 25% of the labeled data is used.
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