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Physics Condensed Matter Materials Science

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Thursday 6 November

Materials Science

Photo-induced switching of magnetisation in the epsilon-near-zero regime

Héloïse Damas, Carl S. Davies, Petr M. Vetoshko et al. (+3 more)

The possibility of controlling spins using ultrashort light and strain pulses has triggered intense discussions about the mechanisms responsible for magnetic re-ordering. All-optical magnetisation switching can be achieved through ultrafast heat-driven demagnetisation or transient modifications of magnetic anisotropy. During the phononic switching of magnetic dielectrics, however, mid-infrared optical excitations can modify the crystal environment via both the thermal quenching of anisotropy and the generation of strain respectively, with the relative distinction between these thermal and non-thermal processes remaining an open question. Here, we examine the effect of mid-infrared pulses tuned to the frequency of optical phonon resonances on the labyrinthine domain structure of a cobalt-doped yttrium iron garnet film. We find that the labyrinthine domains are transformed into stable parallel stripes, and quantitative micromagnetic calculations demonstrate this stems predominantly from a partial quenching of the anisotropy. Contrary to conventional wisdom, however, we find that this heat-facilitated process of magnetisation switching is spectrally strongest not at the maximum of absorbed optical energy but rather at the epsilon-near-zero points. Our results reveal that the epsilon-near-zero condition provides an alternative pathway for laser-driven control of magnetisation, even when the underlying mechanism is primarily thermal.
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All authors Héloïse Damas, Carl S. Davies, Petr M. Vetoshko, Vladimir I. Belotelov, Andrzej Stupakiewicz, Andrei Kirilyuk

Materials Science · Cross-listed from physics.ins-det

Impact of the lead factor of neutron irradiation on the magnetic properties of RPV steels

Sebastián Passanante, Dafne Goijman, M. R. Neyra Astudillo et al. (+5 more)

Materials used in nuclear reactors are constantly exposed to the effects of neutron irradiation, which leads to changes in their mechanical properties. In particular, the steels employed in reactor pressure vessels experience a reduction in the ductile-to brittle transition temperature. Given that the pressure vessel is a non-redundant component, understanding this phenomenon is of significant interest. In this work, we focus on studying the effects of accelerated irradiation by maintaining constant neutron fluence while varying neutron flux, which results in different lead factors. This approach enables the extrapolation of accelerated test results to real operational conditions of the reactor pressure vessels. In our study, we analyzed irradiated steels using three magnetic techniques. Each technique responds differently to the microstructural changes induced by irradiation, allowing for a better characterization of its effects on the material. Through DC magnetometry, the analysis of minor loops shows that the remanence, coercivity, and saturation of the steel depend not only on the fluence with which the material was irradiated but also on the irradiation rate, which means, more specifically, on the lead factor. The AC susceptibility technique shows that the response of the irradiated steel to the applied magnetic field increases with fluence but also with the lead factor. For the real part of XAC, there is an increase with the lead factor, while the imaginary component of XAC grows with the size of the nanoprecipitates. Finally, Barkhausen noise measurements show a clear increase in the RMS of the signal with the lead factor.
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All authors Sebastián Passanante, Dafne Goijman, M. R. Neyra Astudillo, Carlos D. Anello, Rodolfo Kempf, Julián Milano, Martín Gómez, Joaquín Sacanell

Materials Science · Cross-listed from physics.flu-dyn

Stresses and fluid flow in lamina cribrosa through anisotropic poroelasticty

Riccardo Cavuoto, Sofia Damian, Luca Deseri et al. (+5 more)

To investigate the mechanical correlations between intraocular pressure (IOP) variations and glaucoma, this study presents a linear transversely isotropic poroelastic model of the lamina cribrosa (LC) based on Reissner-Mindlin plate theory. A key feature of the proposed framework is its analytical tractability, which allows the governing poroelastic equations to be solved in closed form under appropriate mechanical and hydraulic boundary conditions. Within this setting, linearity is used to capture the reversible component of the tissue response, providing a baseline description of the coupled solid-fluid feedback on which more complex time-dependent phenomena, such as viscoelastic effects and remodelling, may build.The results indicate that both strain and stress measures (in the form of shear strain and deviatoric stress measures) peak in the peripheral region of the LC, which is currently suspected to be the initial site of glaucomatous damage. These quantities increase with IOP, suggesting a pressure-dependent mechanical insult to the retinal ganglion cell (RGC) axons. In parallel, the model predicts a monotonic reduction in fluid content as IOP rises, which may contribute to ischemic phenomena and disc haemorrhages. The influence of material anisotropy was also examined, revealing that isotropic assumptions tend to overestimate the fluid content while underestimating shear strain. Given the current experimental challenges in measuring blood flow within the LC, the proposed model provides a valuable framework for exploring the coupled mechanical-hemodynamic behavior of the tissue and for inverse estimation of its mechanical parameters, such as the stiffness of the opening for the central retinal vessels.
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All authors Riccardo Cavuoto, Sofia Damian, Luca Deseri, Massimiliano Fraldi, Alon Harris, Brent Siesky, Alice Verticchio, Giovanna Guidoboni

Materials Science

Phase controlled multi-terminal Josephson junction in ternary hybrid nanowire

Sabbir A. Kahn, Lukas Stampfer, Sara Marti-Sanchez et al. (+7 more)

This work presents multiterminal Josephson junctions in hybrid semiconductor-superconductor InAsSb-Al nanocrosses. Hybrid nanocrosses are grown using molecular beam epitaxy and are formed through As-assisted merging of oppositely directed InAsSb nanowires. We explain this complex ternary merging mechanism using a temperature-dependent phase diagram and investigate the detailed crystal structure with atomic-resolution imaging. The hybrid nanoscrosses enabled the fabrication of multiterminal Josephson junction devices, which were characterized at low temperatures. The supercurrent through each terminal combination was measured as a function of the density in the junction and the relative phase of the terminals, which was controlled by an external magnetic field.
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All authors Sabbir A. Kahn, Lukas Stampfer, Sara Marti-Sanchez, Dags Olsteins, Damon James Carrad, Thies Jansen, Jonas Johansson, Jordi Arbiol, Peter Krogstrup, Thomas Sand Jespersen

Materials Science

The phase-field model of fracture incorporating Mohr-Coulomb, Mogi-Coulomb, and Hoek-Brown strength surfaces

S Chockalingam, Adrian Buganza Tepole and Aditya Kumar

Classical phase-field theories of brittle fracture capture toughness-controlled crack growth but do not account for the material's strength surface, which governs fracture nucleation in the absence of cracks. The phase-field formulation of Kumar et al. (2020) proposed a blueprint for incorporating the strength surface while preserving toughness-controlled propagation by introducing a nucleation driving force and presented results for the Drucker-Prager surface. Following this blueprint, Chockalingam (2025) recently derived a general driving-force expression that incorporates arbitrary strength surfaces. The present work implements this driving force within a finite-element framework and incorporates representative strength surfaces that span diverse mathematical and physical characteristics-the Mohr-Coulomb, 3D Hoek-Brown, and Mogi-Coulomb surfaces. Through simulations of canonical fracture problems, the formulation is comprehensively validated across fracture regimes, capturing (i) nucleation under uniform stress, (ii) crack growth from large pre-existing flaws, and (iii) fracture governed jointly by strength and toughness. While the strength surfaces examined here already encompass a broad range of brittle materials, the results demonstrate the generality and robustness of the proposed driving-force construction for materials governed by arbitrary strength surfaces.
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Materials Science

Band Alignment Tuning from Charge Transfer in Epitaxial SrIrO$_3$/SrCoO$_3$ Superlattices

Jibril Ahammad, Brian B. Opatosky, Tanzila Tasnim et al. (+6 more)

Understanding charge transfer at oxide interfaces is crucial for designing materials with emergent electronic and magnetic properties, especially in systems where strong electron correlations and spin-orbit coupling coexist. SrIrO$_3$/SrCoO$_3$ (SIO/SCO) superlattices offer a unique platform to explore these effects due to their contrasting electronic structures and magnetic behaviors. Building on past theory based on continuity of O 2p band alignment, we employ density functional theory (DFT) to model electron transfer from Ir to Co across the SIO/SCO interface. To characterize these effects, we synthesized epitaxial SIO/SCO superlattices via molecular beam epitaxy. Structural and transport measurements confirmed high crystallinity, metallic behavior, and suppression of Kondo scattering that has been reported in uniform SIO films. Further characterization via X-ray absorption spectroscopy (XAS) revealed orbital anisotropy and valence changes consistent with interfacial charge transfer. Co K- and L$_{2,3}$-edge and Ir L$_2$-edge spectra verified electron donation from Ir to Co, stabilizing the perovskite SCO phase and tuning the electronic structure of SIO via hole-doping. O K-edge XAS showed band alignment shifts in the SIO layer consistent with DFT predictions. Our work here provides a pathway for engineering oxide heterostructures with tailored magnetic and electronic properties.
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All authors Jibril Ahammad, Brian B. Opatosky, Tanzila Tasnim, John W. Freeland, Gabriel Calderon Ortiz, Jinwoo Hwang, Gaurab Rimal, Boris Kiefer, Ryan B. Comes

Materials Science

A copper sulfide-hydroxypropyl $\beta$-Cyclodextrin-reduced graphene oxide composite for highly sensitive electrochemical detection of 5-hydroxytryptamine in biological samples

Aravindan Santhan, Kuo Yuan Hwa, Slava V. Rotkin et al. (+2 more)

The precise identification of neurotransmitters is essential for comprehending cerebral function, detecting neurological conditions, and formulating successful therapeutic approaches. The present work investigates the electrochemical detection of serotonin with the excellent hybrid electrocatalyst $Cu_2S/H{\beta}cd-rGO$. $Cu_2S$, with its significant features as improved catalytic activity and enhanced charge transfer when combined with $H{\beta}cd-rGO$, will enhance the performance. The integration of $Cu_2S$ with $H{\beta}cd-rGO$, regulated by the van der Waals force and the electrostatic interaction, makes it a stable catalyst without disrupting the composite structure. Also, the aggregation of the $Cu_2S/H{\beta}cd$ with the layered sheets of rGO can be highly reduced and resulting in the improvement of the conductivity. Thus, the above features resulted in the improved oxidation response current when fabricated over the glassy carbon electrode (GCE). The SR showed sensitive response at a broad linear range of 0.019 to 0.299 $\mu$M and 4.28 to 403.14 $\mu$M, resulting in a lower limit of detection (LOD) of 1.2 nM or 0.0012 $\mu$M and a sensitivity of about 15.9 $\mu$A ${\mu}M^{-1}$ $cm^{-2}$. The sensor demonstrated excellent selectivity against common interferents, including aminophenol, dopamine, epinephrine, hydroquinone, melatonin, and chlorine. The real sample studies in the biological samples show good recovery values, showing the effectiveness of the as-fabricated sensor. Thus, the cost-efficient and straightforward integration of $Cu_2S/H{\beta}cd-rGO$ will be an outstanding electrocatalyst for detecting SR.
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All authors Aravindan Santhan, Kuo Yuan Hwa, Slava V. Rotkin, Cheng-Han Wang, Chun-Wei Ou

Materials Science

Machine learning-driven elasticity prediction in advanced inorganic materials via convolutional neural networks

Yujie Liu, Zhenyu Wang, Hang Lei et al. (+6 more)

Inorganic crystal materials have broad application potential due to excellent physical and chemical properties, with elastic properties (shear modulus, bulk modulus) crucial for predicting materials' electrical conductivity, thermal conductivity and mechanical properties. Traditional experimental measurement suffers from high cost and low efficiency, while theoretical simulation and graph neural network-based machine learning methods–especially crystal graph convolutional neural networks (CGCNNs)–have become effective alternatives, achieving remarkable results in predicting material elastic properties. This study trained two CGCNN models using shear modulus and bulk modulus data of 10987 materials from the Matbench v0.1 dataset, which exhibit high accuracy (mean absolute error <13, coefficient of determination R-squared close to 1) and good generalization ability. Materials were screened to retain those with band gaps between 0.1-3.0 eV and exclude radioactive element-containing compounds. The final predicted dataset comprises two parts: 54359 crystal structures from the Materials Project database and 26305 crystal structures discovered by Merchant et al. (2023 Nature 624 80). Ultimately, this study completed the prediction of shear modulus and bulk modulus for 80664 inorganic crystals. This work enriches existing material elastic data resources and provides robust support for material design, with all data openly available at https://doi.org/10.57760/sciencedb.j00213.00104.
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All authors Yujie Liu, Zhenyu Wang, Hang Lei, Guoyu Zhang, Jiawei Xian, Zhibin Gao, Jun Sun, Haifeng Song, Xiangdong Ding

Materials Science

The Moving Beam Diffraction Geometry: the DIAD Application of a Diffraction Scanning-Probe

Alberto Leonardi, Andrew James, Christina Reinhard et al. (+6 more)

Understanding the interactions between microstructure, strain, phase, and material behavior is crucial in many scientific fields. However, quantifying these correlations is challenging, as it requires the use of multiple instruments and techniques, often separated by space and time. The Dual Imaging And Diffraction (DIAD) beamline at Diamond is designed to address this challenge. DIAD allows its users to visualize internal structures, identify compositional/phase changes, and measure strain. DIAD provides two independent beams combined at one sample position, allowing quasi-simultaneous X-ray Computed Tomography and X-ray Powder Diffraction. A unique functionality of the DIAD configuration is the ability to perform image-guided diffraction, where the micron-sized diffraction beam is scanned over the complete area of the imaging field of view without moving the specimen. This moving beam diffraction geometry enables the study of fast-evolving and motion-susceptible processes and samples. Here, we discuss the novel moving beam diffraction geometry presenting the latest findings on the reliability of both geometry calibration and data reduction routines used. Our measures confirm diffraction is most sensitive to the moving geometry for the detector position downstream normal to the incident beam. The observed data confirm that the motion of the KB mirror coupled with a fixed aperture slit results in a rigid translation of the beam probe, without affecting the angle of the incident beam path to the sample. Our measures demonstrate a nearest-neighbour calibration can achieve the same accuracy as a self-calibrated geometry when the distance between calibrated and probed sample region is smaller or equal to the beam spot size. We show the absolute error of the moving beam diffraction geometry remains below 0.0001, which is the accuracy we observe for the beamline with stable beam operation.
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All authors Alberto Leonardi, Andrew James, Christina Reinhard, Michael Drakopoulos, Ben Williams, Hans Dehyle, Jacob Filik, Liam Perera, Sharif Ahmed

Materials Science · Cross-listed from physics.optics

Ion-Implanted Erbium in X-cut Thin-film Lithium Niobate: Luminescence and Low-Temperature Response

Daniel Blight, Mason Adshead, Alessandro Prencipe et al. (+3 more)

This study presents a method for deterministic Er3+ doping of x-cut TFLN using focused ion beam (FIB) implantation with sub-100 nm spatial precision, enabling seamless integration of active rare-earth ions into this technologically relevant platform for lithium niobate integrated nanophotonics. Photoluminescence (PL) measurements from implanted regions reveal Stark-split 4f-4f transitions consistent with bulk Er-doped lithium niobate, indicating similar lattice occupation. Temperature-dependent PL measurements from 300 K to 5 K exhibit conventional behaviour down to approximately 50 K, followed by a marked decrease in the emission intensity and lifetime. This anomaly is attributed to a suppression of the pyroelectric response in LiNbO3 at low temperatures, which affects local electric fields and, consequently, Er3+ emission. The sensitivity of the PL response to the modulation frequency and polarization of the 980 nm excitation light is also consistent with possible mechanisms linking thermal effects and internal fields arising in the thin film. The results demonstrate a method for the targeted doping with Er3+ ions into the most widely used cut of TFLN for integrated photonic devices and provide further important considerations for their exploitation in cryogenic quantum devices.
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All authors Daniel Blight, Mason Adshead, Alessandro Prencipe, Mayam Sanaee, Katia Gallo, Richard J Curry

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

High luminescence efficiency of multi-valley excitonic complexes in heavily doped WSe2 monolayer

Sébastien Roux, Tilly Guyot, Abraao Cefas Torres-Dias et al. (+9 more)

Monolayers of group-VI transition-metal dichalcogenides (TMDs) are two-dimensional semiconductors that exhibit exceptionally strong light-matter coupling yet typically suffer from low emission quantum yields. In this letter, we investigate the heavily n-doped regime of a WSe$_2$ monolayer and show that multi-particle excitonic complexes produce photoluminescence signals up to two orders of magnitude stronger than in the neutral state. Time-resolved photoluminescence and differential reflectivity measurements reveal that the quantum yield rises with carrier density and exceeds 50% for electron concentrations above 10$^{13}$ cm$^{-2}$. These findings establish TMD monolayers as a platform for exploring excitonic complexes in high-density electron gases and point toward new opportunities for efficient, atomically thin light emitters.
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All authors Sébastien Roux, Tilly Guyot, Abraao Cefas Torres-Dias, Delphine Lagarde, Laurent Lombez, Dinh Van Tuan, Junghwan Kim, Kenji Watanabe, Xavier Marie, Takashi Taniguchi, Hanan Dery, Cedric Robert

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

T-square electric resistivity and its thermal counterpart in RuO$_2$

Yu Ling, Florent Pawula, Ramzy Daou et al. (+2 more)

We present a study of low-temperature electric and thermal transport in RuO$_2$, a metallic oxide which has attracted much recent attention. Careful scrutiny of electric resistivity reveals a quadratic temperature dependence below $\sim$ 20 K undetected in previous studies of electronic transport in this material. The prefactor of this T$^2$ resistivity, given the electronic specific heat, corresponds to what is expected by the Kadowaki-Woods scaling. The variation of its amplitude across 4 different samples is negligible despite an eightfold variation of residual resistivity. There is also a T$^5$ resistivity due to scattering by phonons. By measuring thermal conductivity, $\kappa$, at zero field and at 12 T, we separated its electronic and the phononic components and found that the electronic component respects the Wiedemann-Franz law at zero temperature and deviates downward at finite temperature. The latter corresponds to a threefold discrepancy between the prefactors of the two (thermal and electric) T-square resistivities. Our results, establishing RuO$_2$ as a weakly correlated Fermi liquid, provide new input for the ongoing theoretical attempt to give a quantitative account of electron-electron scattering in metallic oxides starting from first principles.
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All authors Yu Ling, Florent Pawula, Ramzy Daou, Benoît Fauqué, Kamran Behnia

Materials Science

Revealing the innate sub-nanometer porous structure of carbon nanomembranes with molecular dynamics simulations and highly charged ion spectroscopy

Filip Vuković, Anna Niggas, Levin Mihlan et al. (+8 more)

Carbon nanomembranes (CNMs) are nanometer-thin disordered carbon materials that are suitable for a range of applications, from energy generation and storage, through to water filtration. The structure-property relationships of these nanomembranes are challenging to study using traditional experimental characterization techniques, primarily due to the radiation-sensitivity of the free-standing membrane. Highly charged ion spectroscopy is a novel characterization method that is able to infer structural details of the carbon nanomembrane without concern of induced damage affecting the measurements. Here we employ molecular dynamics simulations to produce candidate structural models of terphenylthiol-based CNMs with varying degrees of nanoscale porosity, and compare predicted ion charge exchange data and tensile moduli to experiment. The results suggest that the in-vacuum CNM composition likely comprises a significant fraction of under-coordinated carbon, with an open sub-nanometer porous structure. Such a carbon network would be reactive in atmosphere and would be presumably stabilized by hydrogen and oxygen groups under atmospheric conditions.
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All authors Filip Vuković, Anna Niggas, Levin Mihlan, Zhen Yao, Armin Gölzhäuser, Louise Fréville, Vladislav Stroganov, Andrey Turchanin, Jürgen Schnack, Nigel A. Marks, Richard A. Wilhelm

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

High-Tc superconductivity above 130 K in cubic MH4 compounds at ambient pressure

Xinxin Li, Weishuo Xu, Zengguang Zhou et al. (+6 more)

Hydrides have long been considered promising candidates for achieving room-temperature superconductivity; however, the extremely high pressures typically required for high critical temperatures remain a major challenge in experiment. Here, we propose a class of high-Tc ambient-pressure superconductors with MH4 stoichiometry. These hydrogen-based compounds adopt the bcc PtHg4 structure type, in which hydrogen atoms occupy the one-quarter body-diagonal sites of metal lattices, with the metal atoms acting as chemical templates for hydrogen assembly. Through comprehensive first-principles calculations, we identify three promising superconductors, PtH4, AuH4 and PdH4, with superconducting critical temperatures of 84 K, 89 K, and 133 K, respectively, all surpassing the liquid-nitrogen temperature threshold of 77 K. The remarkable superconducting properties originate from strong electron-phonon coupling associated with hydrogen vibrations, which in turn arise from phonon softening in the mid-frequency range. Our results provide crucial insights into the design of high-Tc superconductors suitable for future experiments and applications at ambient pressure.
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All authors Xinxin Li, Weishuo Xu, Zengguang Zhou, Jingming Shi, Hanyu Liu, Yue-Wen Fang, Wenwen Cui, Yinwei Li, Miguel A. L. Marques

Materials Science

Unconventional Thermal Expansion in quasi-one-dimensional monoclinic BaIrO$_3$

Jeong Jinwon, Chang Bin, Noh Han-Jin et al. (+1 more)

We have investigated the temperature dependence of the crystal structure of quasi-one-dimensional monoclinic BaIrO$_3$ using X-ray diffraction. Diffraction patterns were measured across a temperature range from 13 K to 300 K, with 5-degree steps, and Rietveld refinements were performed to extract the relevant lattice parameters. The resulting cell volumes exhibit a significant deviation from the Debye model predictions for lattice-specific heat within a reasonable range of the Debye temperature, Grüneisen parameter, and bulk modulus. This suggests an invar-like, unconventional thermal expansion behavior. The deviation begins near the weak ferromagnetic transition temperature, indicating a strong correlation with changes in the electronic and magnetic structure of monoclinic BaIrO$_3$.
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All authors Jeong Jinwon, Chang Bin, Noh Han-Jin, Lee Seongsu

Materials Science

TXL Fusion: A Hybrid Machine Learning Framework Integrating Chemical Heuristics and Large Language Models for Topological Materials Discovery

Arif Ullah, Rajibul Islam, Yangming Huang et al. (+4 more)

Topological materials, including topological insulators (TIs) and topological semimetals (TSMs), offer promising platforms for quantum, spintronic, and low-dissipation electronic technologies. Their discovery, however, remains constrained by the high cost of first-principles calculations and the slow, resource-intensive nature of experimental validation. Here, we introduce TXL Fusion, a hybrid machine-learning framework that integrates chemically inspired heuristics, physically interpretable numerical descriptors, and large language model (LLM)-derived semantic embeddings for topological-materials classification and discovery. By combining space-group symmetry, electron-count and orbital descriptors, composition-derived topological heuristics, and physics-aware semantic representations, TXL Fusion classifies materials into trivial, TSM, and TI categories with improved overall performance and enhanced minority-class TI recognition relative to conventional descriptor-based baselines. The model further serves as a high-throughput pre-screening tool for external discovery spaces, rapidly prioritizing candidate TSMs before expensive first-principles or experimental validation. Representative TXL-prioritized candidates were subsequently supported by density functional theory (DFT) calculations, demonstrating the practical value of the framework for reducing discovery cost. By uniting symbolic chemical rules, statistical learning, and language-based representations, TXL Fusion provides a scalable and interpretable strategy for accelerating the discovery of next-generation topological and quantum materials.
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All authors Arif Ullah, Rajibul Islam, Yangming Huang, Ghulam Hussain, Zahir Muhammad, Xiaoguang Li, Ming Yang

Materials Science

KAN-Enhanced Contrastive Learning Accelerating Crystal Structure Identification from XRD Patterns

Chenlei Xu, Tianhao Su, Jie Xiong et al. (+6 more)

Accurate determination of crystal structures is central to materials science, underpinning the understanding of composition-structure-property relationships and the discovery of new materials. Powder X-ray diffraction is a key technique in this pursuit due to its versatility and reliability. However, current analysis pipelines still rely heavily on expert knowledge and slow iterative fitting, limiting their scalability in high-throughput and autonomous settings. Here, we introduce a physics-guided contrastive learning framework termed as XCCP. It aligns powder diffraction patterns with candidate crystal structures in a shared embedding space to enable efficient structure retrieval and symmetry recognition. The XRD encoder employs a dual-expert design with a Kolmogorov-Arnold Network projection head, one branch emphasizes low angle reflections reflecting long-range order, while the other captures dense high angle peaks shaped by symmetry. Coupled with a crystal graph encoder, contrastive pretraining yields physically grounded representations. XCCP demonstrates strong performance across tasks, with structure retrieval reaching 0.89 and space group identification attains 0.93 accuracy. The framework further generalizes to compositionally similar multi principal element alloys and demonstrates zero-shot transfer to experimental patterns. These results establish XCCP as a robust, interpretable, and scalable approach that offers a new paradigm for X-ray diffraction analysis. XCCP facilitates high-throughput screening, rapid structural validation and integration into autonomous laboratories.
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All authors Chenlei Xu, Tianhao Su, Jie Xiong, Yue Wu, Shuya Dong, Tian Jiang, Mengwei He, Shuai Chen, Tong-Yi Zhang

Materials Science · Cross-listed from cond-mat.dis-nn

Enhanced stochasticity in irradiated vanadium oxide oscillators

Nareg Ghazikhanian, David J. Alspaugh, Pavel Salev et al. (+3 more)

Insulator-to-metal transition materials are highly sensitive to even minute deviations of stoichiometry, lattice defects, and disorder, which provides opportunities to engineer their electrical switching characteristics. Using V2O3 as a prototypical metal-insulator transition resistive switching material, we demonstrate that localized focused ion beam irradiation can induce stochastic oscillatory dynamics in simple two-terminal switching devices. After irradiating the material, we observed an unusual dynamic regime where the voltage induced metallic state momentarily collapses into an insulating state, which results in a rapid current flickering that is qualitatively different from the conventional current spiking in a Pearson-Anson type oscillatory circuit implemented using the pristine material. Furthermore, the current flickering timing in the irradiated devices becomes progressively more random and more sparse with increasing input voltage, resulting in nonlinear and nondeterministic oscillatory behavior. The irradiation also leads to a dramatic reduction in switching power required to induce the current oscillations. These results are elucidated through random resistor network simulations which indicate that a small number of local sites can control the electrical metal-insulator transition switching properties in large devices with high defect concentration. Our results show that selective focused ion beam irradiation provides exciting prospects for engineering and tuning novel stochastic behaviors in emergent technologies that rely on the intrinsic randomness of physical processes.
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All authors Nareg Ghazikhanian, David J. Alspaugh, Pavel Salev, Lorenzo Fratino, Marcelo J. Rozenberg, Ivan K. Schuller

Materials Science

All-optical magnetization reversal via x-ray magnetic circular dichroism

Kihiro T. Yamada, Akira Izumi, Tetsuya Ikebuchi et al. (+15 more)

Light polarization is one of the most fundamental features, equivalent to energy and coherence. Magnetism changes light polarization, and vice versa. The irradiation of intense circularly polarized femtosecond pules to magnetic materials can alter the magnetic orders and elementary excitations, particularly in the visible to infrared spectral regions. Furthermore, the recent development of x-ray free-electron laser enables the element-specific trace of the ultrafast dynamics with high time and spatial resolution. However, the light helicity of x-ray photons has not yet been used to control order parameters in condensed matter materials, not limited to such magnetic phenomenon. Here, we demonstrate the deterministic magnetization reversal of a ferromagnetic Pt/Co/Pt multilayer solely by irradiating femtosecond pulses of circularly polarized hard x-rays. The observed all-optical magnetization switching depends on the helicity of incident x-ray pulses and is strongly resonant with the photon energy at the Pt $L_3$ edge. These results originate in the x-ray magnetic circular dichroism of Pt, involving helicity-dependent excitation from the 2$p_{3/2}$ core level to the exchange-split 5$d$ valence states owing to the magnetic proximity effect with Co. These findings mark a new frontier for examining interactions between light and matter in the x-ray region.
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All authors Kihiro T. Yamada, Akira Izumi, Tetsuya Ikebuchi, Sumiyuki Okabe, Masaki Kubo, Ryusei Obata, Rei Kobayashi, Yuya Kubota, Takuo Ohkochi, Naomi Kawamura, Kotaro Higashi, Yoichi Shiota, Takahiro Moriyama, Teruo Ono, Iwao Matsuda, Tadashi Togashi, Yoshihito Tanaka, Motohiro Suzuki

Materials Science · Cross-listed from physics.ins-det

Robust electron counting for direct electron detectors with the Back-Propagation Counting method

Joshua Renner, Matthew A. Wright, Kristofer Bouchard et al. (+6 more)

Electron microscopy (EM) is a foundational tool for directly assessing the structure of materials. Recent advances in direct electron detectors have improved signal-to noise ratios via single-electron counting. However, accurately counting electrons at high fluence remains challenging. We developed a new method of electron counting for direct electron detectors, Back-Propagation Counting (BPC). BPC uses machine learning techniques designed for mathematical operations on large tensors but does not require large training datasets. In synthetic data, we show BPC is able to count multiple electron strikes per pixel and is robust to increasing occupancy. In experimental data, frames counted with BPC are shown to reconstruct diffraction peaks corresponding to individual nanoparticles with relatively higher intensity and produce images with improved contrast when compared to a standard counting method. Together, these results show that BPC excels in experiments where pixels see a high flux of electron irradiation such as in situ TEM movies and diffraction.
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All authors Joshua Renner, Matthew A. Wright, Kristofer Bouchard, Bruce E. Cohen, Peter Ercius, Azriel Goldschmidt, Cassio C.S. Pedroso, Ambarneil Saha, Peter Denes

Wednesday 5 November

Materials Science · Cross-listed from quant-ph

Controlled growth of rare-earth-doped TiO$_{2}$ thin films on III-V semiconductors for hybrid quantum photonic interfaces

Henry C. Hammer, Caleb Whittier, Nathan A. Helvy et al. (+3 more)

Quantum photonic networks require two distinct functionalities: bright single-photon sources and long-lived quantum memories. III-V semiconductor quantum dots excel as deterministic and coherent photon emitters, while rare-earth ions such as erbium (Er$^{3+}$) in crystalline oxides offer exceptional spin and optical coherence at telecom wavelengths. Combining these systems and their functionalities via direct epitaxy is challenging due to lattice mismatch and incompatible growth conditions. Here we demonstrate low-temperature pulsed laser deposition of Er$^{3+}$-doped TiO$_{2}$ thin films directly on GaAs and GaSb substrates. Controlled surface preparation with an arsenic cap and an oxygen-deficient buffer layer enables the growth of epitaxial anatase TiO$_{2}$ (001) at 390$^{o}$C with sub-300 pm surface roughness, while avoiding interface degradation. In contrast, high-temperature oxide desorption or growth temperatures drive the transition to rough, polycrystalline rutile film, as confirmed by transmission electron microscopy. Minimal coincident interface area (MCIA) modeling explains the orientation-selective growth on GaAs and GaSb. Raman and cryogenic photoluminescence excitation spectroscopy verify the crystal phase and optical activation of Er$^{3+}$ ions. This multi-parameter growth strategy helps preserve III-V quantum dot functionality and yields smooth surfaces suitable for low-loss nanophotonic structures. Our results establish a materials platform for monolithically integrating rare-earth quantum memories with semiconductor photon sources, paving the way toward scalable hybrid quantum photonic chips.
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All authors Henry C. Hammer, Caleb Whittier, Nathan A. Helvy, Christopher Rouleau, Nabil D. Bassim, Ravitej Uppu

Materials Science

Unconventional cross sections in zinc phosphide nanowires grown using exclusively earth-abundant components

Simon Escobar Steinvall, Hampus Thulin, Nico Kawashima et al. (+8 more)

To enable lightweight and flexible solar cell applications it is imperative to develop direct bandgap absorber materials. Moreover, to enhance the potential sustainability impact of the technologies there is a drive to base the devices on earth-abundant and readily available elements. Herein, we report on the epitaxial growth of Zn3P2 nanowires using exclusively earth-abundant components, using Sn as the nanowire catalyst and Si (111) as the substrate. We observe that the nanowires exhibit a triangular cross section at lower temperatures, a pseudo-pentagonal cross section at intermediate temperatures, and a hexagonal cross section in a twin plane superlattice configuration at high temperatures and high V/II ratios. At low temperatures, the surface facets are constricted into a metastable configuration, yielding the triangular morphology due to the symmetry of the substrate, while intermediate temperatures facilitate the formation of a pseudo-pentagonal morphology with lower surface to volume ratio. The twin plane superlattice structure can only be observed at conditions that facilitate the incorporation of Sn into Zn3P2, which is needed to form heterotwins in the tetragonal structure, namely at high temperatures and high phosphine partial pressures. These findings show a clear pathway to use Zn3P2 nanowires in sustainable solar energy harvesting using exclusively earth-abundant components, as well as opening up a novel route of fabricating quantum wells inside nanowires using heterotwins.
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All authors Simon Escobar Steinvall, Hampus Thulin, Nico Kawashima, Francesco Salutari, Jonas Johansson, Aidas Urbonavicius, Sebastian Lehmann, Maria Chiara Spadaro, Jordi Arbiol, Silvana Botti, Kimberly A. Dick

Materials Science

Learning to shine: Neuroevolution enables optical control of phase transitions

Sraddha Agrawal, Stephen Whitelam and Pierre Darancet

We address active optical steering of structural phase transitions in solids. We demonstrate that existing evolutionary reinforcement learning approaches can derive optimal time-dependent electric fields in driven dissipative classical systems far beyond the harmonic regime, enabling the stabilization of non-thermal structural phases. Our approach relies on experimentally-extractable metrics of the phase-space evolution and interpretable Fourier Neural Network surrogates of the electric field. Using this method on first-principles models, we obtain protocols stabilizing a symmetric phase in bismuth through impulsive Raman and displacive excitations with continuous and pulsed light sources in the presence of dissipation and thermal disorder. The method is gradient-free, enabling optimization loops based solely on experimental data and providing a practical route for controlling light-induced structural dynamics independently of the microscopic model of light-matter interactions.
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Materials Science

Scalable Autoregressive Deep Surrogates for Dendritic Microstructure Dynamics

Kaihua Ji, Luning Sun, Shusen Liu et al. (+2 more)

Microstructural pattern formation, such as dendrite growth, occurs widely in materials and energy systems, significantly influencing material properties and functional performance. While the phase-field method has emerged as a powerful computational tool for modeling microstructure dynamics, its high computational cost limits its integration into practical materials design workflows. Here, we introduce a machine-learning framework using autoregressive deep surrogates trained on short trajectories from quantitative phase-field simulations of alloy solidification in limited spatial domains. Once trained, these surrogates accurately predict dendritic evolution at scalable length and time scales, achieving a speed-up of more than two orders of magnitude. Demonstrations in isothermal growth and in directional solidification of a dilute Al-Cu alloy validate their ability to predict microstructure evolution. Quantitative comparisons with phase-field benchmarks further show excellent agreement in the tip-selection constant, morphological symmetry, and primary spacing evolution.
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All authors Kaihua Ji, Luning Sun, Shusen Liu, Fei Zhou, Tae Wook Heo

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

Vortex-Controlled Quasiparticle Multiplication and Self-Growth Dynamics in Superconducting Resonators

Joong M. Park, Martin Mootz, Richard H. J. Kim et al. (+11 more)

Even in the quantum limit, non-equilibrium quasiparticle (QP) populations induce QP poisoning that irreversibly relaxes the quantum state and significantly degrades the coherence of transmon qubits. A particularly detrimental yet previously unexplored mechanism arises from QP multiplication facilitated by vortex trapping in superconducting quantum circuits, where a high-energy QP relaxes by breaking additional Cooper pairs and amplifying the QP population due to the locally reduced excitation gap and enhanced quantum confinement within the vortex core. Here we directly resolve this elusive QP multiplication process by revealing vortex-controlled QP self-generation in a highly nonequilibrium regime preceding the phonon bottleneck of QP relaxation. At sufficiently low fluence, femtosecond-resolved magneto-reflection spectroscopy directly reveals a continuously increasing QP population that is strongly dependent on magnetic-field-tuned vortex density and absent at higher excitation fluences. Quantitative analysis of the emergent QP pre-bottleneck dynamics further reveals that, although the phonon population saturates within $\simeq$10~ps, both free and trapped QPs continue to grow in a self-sustained manner–hallmarks of the long-anticipated QP-vortex interactions in nonequilibrium superconductivity. We estimate a substantial increase of $\sim$34% in QP density at vortex densities of $\sim$ 100 magnetic flux quanta per $\mathrm{\mu m^{2}}$. Our findings establish a powerful spectroscopic tool for uncovering QP multiplication and reveal vortex-assisted QP relaxation as a critical materials bottleneck whose mitigation will be essential for resolving QP poisoning and enhancing coherence in superconducting qubits.
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All authors Joong M. Park, Martin Mootz, Richard H. J. Kim, Zhixiang Chong, Samuel Haeuser, Randall K. Chan, Liang Luo, Dominic P. Goronzy, Mark C. Hersam, Ilias E. Perakis, Akshay A Murthy, Alexander Romanenko, Anna Grassellino, Jigang Wang

Materials Science

Crystallization Behavior of ZBLAN Glass Under Combined Thermal and Vibrational Effects: Part II - COMSOL Simulation and Apparatus Redesign

Ayush Subedi, Anthony Torres and Jeff Ganley

In Part I of this study, vibration assisted heat treatments of ZBLAN glass revealed irregular crystallization at higher vibration levels, attributed to intermittent loss of thermal contact between the sample and the inner silica ampoule wall. The present work (Part II) investigates this mechanism through finite element modeling (FEM) and experimental validation.COMSOL Multiphysics simulations incorporating conduction, radiation, and contact resistance confirm that intermittent contact markedly reduces heat transfer efficiency, lowering the sampletemperature. To mitigate this effect, the experimental setup was redesigned with a four-degree inclination to maintain stable contact during vibration. Subsequent experiments at vibration levels H3-H5 demonstrated uniform heating and consistent crystallization behavior.Comprehensive microscopic, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and Atomic Force Microscopy (AFM) analyses revealed that even at subtle vibration levels (~50 Hz), partially crystallized ZBLAN transformed into well-developed crystalline structures near 360C. With increasing vibration amplitude, amorphous ZBLAN began forming incipient crystalline phases around 330C, and at higher frequencies (~100 Hz), partial crystallization initiated at approximately 350C. These results indicate that higher vibration frequencies accelerate nucleation, enhance heat transfer, and reduce the effective fiber-drawing temperature window by about 30C. Prolonged exposure above 330C under vibration promotes unwanted phase transitions, emphasizing the need for precise thermal and vibrational control. This study establishes a predictive framework for vibration-resistant ZBLAN processing applicable to both terrestrial and microgravity environments.
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Materials Science

A data-driven quest for room-temperature bulk plastically deformable ceramics

Iwo Słodczyk, Alexander Frisch, Xufei Fang et al. (+2 more)

The growing number of ceramics exhibiting bulk plasticity at room temperature has renewed interest in revisiting plastic deformation and dislocation-mediated mechanical and functional properties in these materials. In this work, a data-driven approach is employed to identify the key parameters governing room-temperature bulk plasticity in ceramics. The model integrates an existing dataset of 55 ceramic materials, 38 plastically deformable and 17 brittle, and achieves accurate classification of bulk plasticity. The analysis reveals several key parameters essential for predicting bulk plasticity: i) Poisson's ratio and Pugh's ratio as macroscopic indicators reflecting the balance between shear and volumetric deformation resistance, and ii) Burgers vector, crystal structure and melting temperature as crystallographic descriptors associated with lattice geometry, slip resistance and thermal stability, and iii) Bader charge as a microscopic measure of bonding character. Together, these parameters define a multiscale descriptor space linking intrinsic materials properties to bulk room-temperature plasticity in ceramics, bridging the gap between empirical ductility criteria and atomistic mechanisms of dislocation-mediated plasticity. While preliminary, this study provides the first systematic, data-driven mapping of the governing factors of ceramic plasticity. The resulting framework establishes a foundation for unifying experimental and computational studies through shared datasets and descriptors, fostering collective progress toward understanding and designing intrinsically ductile ceramics.
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All authors Iwo Słodczyk, Alexander Frisch, Xufei Fang, Inna Gitman, Fengxian Liu

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

Ultrasmall (3,0) carbon nanotube: a superconducting unit with strong electron-phonon coupling

Zhenfeng Ouyang, Jing Jiang, Jian-Feng Zhang et al. (+3 more)

Based on density-functional first-principles calculations, we study the electronic structures, lattice dynamics, and electron-phonon coupling (EPC) properties of the ultrasmall one-dimensional (3,0) carbon nanotube (CNT). Our studies reveal that the (3,0) CNT hosts characteristic collective phonon modes, in which the corresponding atomic vibrations can significantly modulate the electronic self-consistent potential and induce strong EPC. Our results further show that the (3,0) CNT exhibits robust phonon-mediated superconductivity under ambient pressure, with a superconducting transition temperature reaching $\sim$ 33 K ($\mu^*$ = 0.10). We also find that although hole doping enhances the density of states (DOS) near the Fermi level, it simultaneously hardens the strongly coupled phonon modes and suppresses the total EPC. This result indicates that phonons play a more crucial role in the superconductivity of ultrasmall CNTs rather than the DOS alone. Therefore, we suggest that the ultrasmall (3,0) CNT can serve as a superconducting unit hosting phonon modes with strong EPC, and propose a strategy for discovering new phonon-mediated superconductors by identifying superconducting units.
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All authors Zhenfeng Ouyang, Jing Jiang, Jian-Feng Zhang, Miao Gao, Kai Liu, Zhong-Yi Lu

Materials Science

Peierls Transition and Magnetism in a Dirac Semimetal: CaMnBi$_2$

Aashish Sapkota, Niraj Aryal, Xiao Hu et al. (+9 more)

Dirac semimetals of the form $A$Mn$X_2$ ($A =$ alkaline-earth or divalent rare earth; $X =$ Bi, Sb) host conducting square-net Dirac-electron layers of $X$ atoms interleaved with antiferromagnetic Mn$X$ layers. Hypervalent pnictogen square nets have long been predicted to host an electronically driven Peierls instability, whereas low-temperature anomalies in CaMnBi$_2$ near $T^{*}\sim 50$~K have previously been discussed in terms of possible magnetic canting, TRS breaking, and a resulting Weyl-semimetal (WSM) state. Here we use polarized and unpolarized neutron diffraction, x-ray diffraction, and density functional theory (DFT) to investigate this transition in single-crystal CaMnBi$_2$. We observe a coupled structural/magnetic symmetry-lowering transition at $T^{*}=46(2)$ K from a tetragonal lattice with C-type antiferromagnetism to an orthorhombic phase with unit-cell doubling along the $c$ axis, minimal impact on magnetism, and no measurable uniform spin canting ($\lesssim 2^\circ$). Superlattice peak intensities and the lattice distortion reveal a continuous second-order transition governed by a single primary order parameter. The refined displacement pattern corresponds to a zigzag bond-order-wave (BOW) modulation of in-plane Bi–Bi bonds, providing direct diffraction evidence for a Peierls-type instability of the Dirac-electron Bi layer anticipated by Hoffmann and co-workers [W. Tremel and R. Hoffmann, J. Am. Chem. Soc. 109, 124 (1987); G. A. Papoian and R. Hoffmann, Angew. Chem. Int. Ed. 39, 2408 (2000)]. These results identify the $T^{*}$ anomaly as an intrinsic Dirac-electron-driven Peierls/BOW transition of the Bi square net.
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All authors Aashish Sapkota, Niraj Aryal, Xiao Hu, Masaaki Matsuda, Yan Wu, Guangyong Xu, John M. Wilde, Andreas Kreyssig, Paul C. Canfield, Cedomir Petrovic, John M. Tranquada, Igor A. Zaliznyak

Materials Science

Intercalation induced quasi-freestanding layer in TiSe$_2$

Turgut Yilmaz, Yi Sheng Ng, Anil Rajapitamahuni et al. (+4 more)

Angle-resolved photoemission spectroscopy is employed to study the electronic structure of bulk TiSe2 before and after doping with potassium impurities. A splitting in the conduction band into two branches is observed after room-temperature deposition. The splitting energy increases to approximately 130 meV when the sample is cooled to 40 K. One branch exhibits a non-dispersive two-dimensional feature, while other one shows the characteristics of three dimensional bulk band dispersion. Core level spectroscopy suggests that the K impurities predominantly occupy the intercalated sites within the van derWaals gap. The results indicate the formation of a quasi-freestandingTiSe2 layer. Additionally, doping completely suppresses the periodic lattice distortion in the surface region. These findings are further supported by density functional theory calculations, which compare the band structure of monolayer and bulk TiSe2 with experimental data. Thus, the dimensional and intrinsic electronic properties of 1T-TiSe2 can be controlled through the intercalation procedure used in this work.
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All authors Turgut Yilmaz, Yi Sheng Ng, Anil Rajapitamahuni, Asish Kundu, Hui-Qiong Wang, Jin-Cheng Zheng, Elio Vescovo