Materials Science
Orbital to charge current conversion in copper oxide heterostructures
S. Vojkovic, K. Cancino, G. Rodríguez et al. (+8 more)
We investigate the orbital-to-charge current conversion in CoFeB|CuO
bilayers as a function of CuO thickness, employing orbital pumping via
ferromagnetic resonance. The dynamic injection of orbital angular momentum into the CuO layer generates a transverse voltage through the Inverse Orbital
Hall Effect (IOHE). By systematically varying the CuO thickness from 2 nm to 30 nm, we observe a pronounced dependence of the IOHE-induced voltage on the CuO layer thickness, indicating efficient orbital-to-charge conversion. These results highlight the key role of the orbital degree of freedom in orbitronics and provide insights into the potential of transition-metal
oxides for next-generation orbitronic devices.
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All authors S. Vojkovic, K. Cancino, G. Rodríguez, E. Burgos, G. Herrera, C. Gonzalez-Fuentes, J. Palma, T. V. M. Sreekanth, J. Denardin, R. L. Rodríguez-Suárez, S. Oyarzún
Materials Science · Cross-listed from cond-mat.mes-hall
Jan Kunc, Bohdan Morzhuk, Veronika Stará et al. (+6 more)
The realization of high-fidelity organic-inorganic
quantum emulators is frequently hindered by the interfacial imperfections introduced during device fabrication. Here, we demonstrate a robust nanofabrication protocol that restores the atomic-scale purity of epitaxial
graphene on SiC to UHV-equivalent levels, as confirmed by Low-Energy Electron Diffraction, and Microscopy. This pristine interface enables the emergence of macroscopic excitonic coherence in epitaxial overlayers of 2,3,6,7,10,11-hexamethoxytriphenylene (HMTP), a model molecular system characterized by intense electron-
phonon coupling. Through a combination of high-sensitivity
Fourier Transform Photo-current Spectroscopy, photoluminescence, and dynamic Raman mapping, we resolve a complex vibronic
manifold governed by Davydov splitting. We show that the $P6_3/m$ crystalline
symmetry of the HMTP overlayer lifts the degeneracy of the HOMO-LUMO transition, creating discrete bright and dark excitonic branches. Using an analytical tight-binding model parameterized by ARPES-derived intermolecular coupling and Raman vibrational modes validated by molecular dynamics simulations, we quantify the polarization energy, the Huang-Rhys factor, and Herzberg-Teller corrections to the Franck-Condon model. Our results reveal that the dark-state branch dominates the radiative channel, following a polaron-mediated relaxation pathway consistent with Kasha's rule. By reconciling macroscopic device architecture with UHV-level surface science, this work establishes a scalable platform for the study of dark-
exciton dynamics and the development of solid-state molecular
quantum memories.
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All authors Jan Kunc, Bohdan Morzhuk, Veronika Stará, Devanshu Varshney, Mykhailo Shestopalov, Kryštof Matějka, Martin Rejhon, Jiří Novák, Jan Čechal
Materials Science
Unraveling Lithium Dynamics in Solid Electrolyte Interphase: From Graph Contrastive Learning to Transport Pathways
Qiye Guan and Yongqing Cai
Fast lithium transport across the solid-state electrolyte (SSE)/lithium metal anode interface is critical for high-performance all-solid-state batteries. Uncovering the complex lithium dynamics governed by diverse local environments in the solid electrolyte interphase (SEI) is fundamental for performance optimization. However, a general framework for characterizing these distinct local environments and the associated transport mechanisms remains lacking. Here, we develop GET-SEI, a general framework that discovers local atomic environments without predefined labels through Graph contrastive learning (GCL), models lithium transition kinetics via Extended dynamic mode decomposition (EDMD), and quantifies reactive lithium flux through Transition path theory (TPT). Applied to different SSE/Li systems, including sulfides (Li6PS5Cl/Li, Li10GeP2S12/Li) and
oxides (Li7La3Zr2O12/Li), the GET-SEI reveals dominant transport pathways and kinetic bottlenecks in each system, providing quantitative metrics for evaluating lithium transport efficiency. As novel high-performance SSEs continue to emerge, GET-SEI offers a widely applicable, interpretable tool for targeted SEI engineering.
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Materials Science
Hsin-Mei Ho, Michael Lorke and Peter Kratzer
Heterostructures composed of transition metal dichalcogenides (TMDCs) and organic molecules have been extensively explored for optoelectronic devices. To maximize their application potential, it is essential to investigate the electronic band structures, which govern the charge response of the interfaces to external perturbations. Based on $GW$ calculations, we present a study of organic-inorganic
heterostructures with anthracene molecules adsorbed on monolayer MoS2. Building on previous investigations of organic molecule self-assembly at surfaces, we systematically analyze anthracene configurations with various molecular orientations and surface coverages. Partially self-consistent $GW_0$ provides qualitatively different level
alignments from those in DFT. Whereas the systems with sparse, horizontally adsorbed anthracenes exhibit type-I
alignment, densely packed anthracenes in the head-on position lead to type-II
alignment, which indicates the strong dependence of quasiparticle corrections on the interfacial configuration. These findings highlight the importance of level-
alignment predictions for both interpreting experiments and guiding the design of organic-inorganic
heterostructures.
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Materials Science
Efficient first-principles modeling of complex molecular crystals at sub-chemical accuracy
Benjamin X. Shi, Kristina M. Herman, Flaviano Della Pia et al. (+5 more)
Molecules can form myriad crystalline polymorphs, each with distinct properties affecting their performance across diverse applications, from pharmaceuticals to functional materials and more. Predicting the thermodynamically most stable polymorph from first principles remains a formidable challenge. It requires methods that scale to large, technologically-relevant molecules while achieving very high accuracy (below 1 kJ/mol) on relative
lattice energies. Such accuracy, often termed sub-chemical accuracy, is generally beyond the reach of the workhorse density functional theory (DFT). In this work, we introduce a framework, combining advances in correlated wavefunction theory (cWFT) and the many-body expansion, to deliver accurate, cost-effective predictions of complex molecular
crystals. For 23 organic molecules and 13 ice polymorphs, we predict
crystal lattice energies to within experimental uncertainties at costs comparable to hybrid DFT, while being several orders of magnitude more efficient than previous cWFT approaches. We extend this approach to a set of large, drug-like molecules including axitinib and ROY, previously inaccessible to cWFT and where DFT is insufficient, achieving sub-chemical accuracy on the relative energies between challenging polymorphs. With the reference data generated throughout this work, we have been able to further parametrize a DFT functional with unprecedented accuracy aligning with our predictions. This cWFT framework as well as DFT functional are made openly available, providing new ranking tools to facilitate efficient high-throughput screening of molecular
crystal polymorphs.
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All authors Benjamin X. Shi, Kristina M. Herman, Flaviano Della Pia, Venkat Kapil, Andrea Zen, Peter R. Nagy, Sotiris Xantheas, Angelos Michaelides
Materials Science
Elucidating different $NO_{2}$ sensing mechanisms in oxidized PbS nanocrystals
Fernando M. Fernandes, Fouad El Haj Hassan, Sophie Hermans et al. (+1 more)
In this work we provide an in-depth analysis of the sensing mechanisms of $NO_{2}$ by lead-sulfide nanocrystals (PbS-NCs). A detailed model for the sorption mechanism is proposed, and the correlation is established between experimental sensing characteristics and the surface composition, based on both experimental characterization and ab initio (DFT) simulations. We demonstrated how the sensitivity and the sensing dynamic response can be tuned by a post-deposition multistep dry-thermal process at mild temperature, that alternates
vacuum-assisted annealing and heating in open-air. Sensors with different surface compositions were fabricated, and their dynamic response was characterized at low concentration of $NO_{2}$ (0.5 ppm) in air, at ambient temperature. DFT simulations indicate that both surface stoichiometry and oxidation critically govern $NO_{2}$ interaction on PbS, with sulfur-rich terminations favoring weaker binding and faster desorption, while intermediate oxidation enhances interaction and overoxidation leads to surface passivation, in agreement with the measured experimental sensing dynamics. By linking surface composition, adsorption chemistry, and resistance transduction within a single framework, this work provides clear indications to design room-temperature, low-ppm $NO_{2}$ microsensors fabricated through a simple and scalable processes.
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All authors Fernando M. Fernandes, Fouad El Haj Hassan, Sophie Hermans, Benoît Hackens
Materials Science
Enhancing Phase Clustering in Nanomechanical Property Maps of Multiphase Materials Using Kernel-Averaged Mechanical Mismatch
David Mercier and Yasmine El Gharoussi
This work presents a novel approach to improve phase identification in nanomechanical property maps of multiphase materials, such as those obtained by nanoindentation or atomic force microscopy (AFM). A major challenge in validating clustering strategies for these data is the lack of ground-truth phase labels in experimental measurements, along with the tendency of overly simplistic synthetic
datasets to artificially inflate
algorithm performance. To address this gap, we construct controlled yet non-trivial synthetic
benchmarks with tunable mechanical contrast, graded interfaces, curved boundaries, and diffuse morphologies, enabling rigorous and realistic evaluation of clustering robustness. Conventional clustering methods based only on elastic modulus (E) and hardness (H) often struggle to separate phases when mechanical contrast is low or when diffuse interphase regions are present. We introduce the Kernel-Averaged Mechanical Mismatch (KAMM), a neighborhood-informed feature that quantifies local mechanical heterogeneity by comparing each point to its neighbors in (E, H) space. When incorporated into a three-dimensional clustering space (E, H, KAMM), this framework improves phase separability, enhances interphase detection, and increases robustness to noise. By enabling more reliable
segmentation of mechanical domains under realistic contrast conditions, the proposed method facilitates the generation of representative volume elements (RVEs) and supports more accurate extraction of phase-specific properties in heterogeneous microstructures.
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Materials Science
High-quality, high-information datasets for universal atomistic machine learning
Cesare Malosso, Filippo Bigi, Paolo Pegolo et al. (+7 more)
The quality, consistency, and information content of training data is often what determines the practical value of machine-learning models for atomistic simulations. Yet, many widely used electronic-structure databases are assembled having materials screening as primary goal rather than robust force-field learning, are limited in their scope to a specific class of chemical compounds, and/or employ inconsistent DFT functionals and settings. Here we introduce MAD-1.6, a highly curated
dataset designed explicitly for training broadly applicable atomistic models across the periodic table at high levels of theory. MAD-1.6 extends the MAD
dataset with targeted enrichment strategies that improve the coverage of chemical space to 102 elements while keeping the total number of configurations compact. All structures are computed with a single, standardized all-electron DFT workflow using the r$^2$SCAN meta-GGA functional and consistent convergence settings, ensuring uniformity across chemically heterogeneous systems. The
dataset encompasses molecules, clusters, bulk
crystals, surfaces, and low-dimensional structures, and its quality and consistency are further enhanced by outlier removal using uncertainty quantification. We demonstrate the high accuracy that can be achieved with the proposed
dataset by training PET-MAD-1.6, a generally applicable r$^2$SCAN interatomic potential that covers 102 elements in the periodic table and achieves exceptional levels of
benchmark accuracy and stability in challenging simulation protocols.
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All authors Cesare Malosso, Filippo Bigi, Paolo Pegolo, Joseph W. Abbott, Philip Loche, Mariana Rossi, Tiago J. Goncalves, Sandip De, Michele Ceriotti, Arslan Mazitov
Materials Science · Cross-listed from cond-mat.mes-hall
Anisotropic two-dimensional magnetoexciton with exact center-of-mass separation
Dang-Khoa D. Le, Hoang-Viet Le, Dai-Nam Le et al. (+4 more)
Excitons in anisotropic two-dimensional (2D) materials, defined by direction-dependent effective masses, are of pronounced interest for their roles in excitonic and magneto-optical phenomena. A perpendicular
magnetic field complicates the separation of center-of-mass (c.m.) and relative motions, especially when electron and hole masses are comparable. Conventional theories often employ an approximate c.m. separation using factorized wave functions, modifying
magnetic Hamiltonian terms and possibly introducing inaccuracies in magnetoexciton energy predictions. This work develops an exact analytical framework for c.m. and relative motion separation in anisotropic 2D magnetoexcitons, without resorting to the stationary-c.m. approximation. Starting from the full electron-hole
Hamiltonian in a homogeneous
magnetic field, the formalism uses the conserved pseudomomentum to derive a relative-motion
Hamiltonian, revealing new anisotropy-dependent couplings and
magnetic coefficients absent in approximate models. The resulting Schrödinger equation is treated via the Feranchuk-Komarov operator method and Levi-Civita transformation, allowing non-perturbative, systematically convergent solutions. Application to monolayer black phosphorus and titanium trisulfide, both freestanding and encapsulated in hexagonal boron nitride, yields magnetoexciton energies, diamagnetic coefficients, and probability densities for the ten lowest states across considerable
magnetic-field ranges. The results demonstrate the significant influence of anisotropy-dependent coupling on
magnetic response in systems with strong mass anisotropy. This formalism is generalizable to other anisotropic 2D
semiconductors, establishing a foundation for advanced magneto-optical studies.
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All authors Dang-Khoa D. Le, Hoang-Viet Le, Dai-Nam Le, Duy-Anh P. Nguyen, Thanh-Son Nguyen, Ngoc-Tram D. Hoang, Van-Hoang Le
Materials Science · Cross-listed from cond-mat.str-el
Tensor-network methodology for real-space super-moiré excitons
Anouar Moustaj, Yitao Sun, Tiago V. C. Antão et al. (+2 more)
Computing excitonic spectra in quasicrystal and super-moiré systems constitutes a formidable challenge due to the exceptional size of the excitonic
Hilbert space. Here, we demonstrate a tensor-network method for the real-space Bethe-Salpeter
Hamiltonian, allowing us to access the spectra of an excitonic $10^{18}$-dimensional
Hamiltonian, and enabling the direct computation of bound-
exciton spectral functions for systems exceeding one billion
lattice sites, several orders of magnitude beyond the capabilities of conventional approaches. Our method combines a tensor-network encoding of the real-space Bethe-Salpeter
Hamiltonian with a Chebyshev tensor network
algorithm. This strategy bypasses explicit storage of the
Hamiltonian while preserving full real-space resolution across widely different length scales. We demonstrate our methodology for one- and two-dimensional super-moiré systems, achieving the simultaneous resolution of atomistic and mesoscopic structures in the excitonic spectra in billion-size systems, showing
exciton miniband formation and moiré-induced spatial confinement. Our results establish a real-space methodology enabling the simulation of excitonic physics in large-scale quasicrystal and super-moiré
quantum matter.
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All authors Anouar Moustaj, Yitao Sun, Tiago V. C. Antão, Lumen Eek, Jose L. Lado
Materials Science
Pathway to lowest-energy structures and stress relaxation for the surface triple junction verified by machine learning
Yuan Fang, Ipen Demirel, Xiaopu Zhang et al. (+3 more)
The behavior of surface triple junctions (STJ) at emergent grain boundaries on free surfaces is critical to the microstructure
evolution, and therefore to the stability of the next generation interconnect. Yet,despite this significant importance, its lowest-energy structure and local stress have remained persistently unknown. Here, we fill this critical gap through high-resolution experimental mapping of the local surface deformation at STJ, the analysis of the local structure and stress relaxation, and ergodic searching metastable structures. We establish the zipped Y-shaped notch as the universal lowest-energy structures. This energetic preference was well explained by the distinctive local stress mechanism and was excellently verified with machine learning methods for a wide range of boundaries. By revealing the elusive thermodynamics of STJs, our findings advance the research field by redefining the energetic framework for capillary driven structure
evolution and providing foundation for understanding kinetically diffusive deformation and for engineering thin-film interconnects and related materials.
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All authors Yuan Fang, Ipen Demirel, Xiaopu Zhang, Yuchuan Shao, Jianda Shao, John J. Boland
Materials Science · Cross-listed from physics.chem-ph
A Relationship between the Molecular Parity-Violation Energy and the Electronic Chirality Measure
Juan J. Aucar, Alessandro Stroppa and Gustavo A. Aucar
When the weak-forces producing parity-violating effects are taken into account, there is a tiny energy difference between the total electronic energies of two enantiomers ($\Delta E_{PV}$), which might be the key to understand the
evolution of the biological homochirality. We focus on the electronic chirality measure ($ECM$), a powerful descriptor based on the electronic charge density, for quantifying the chirality degree of a molecule, for a representative set of
chiral molecules, together with their E$_{PV}$ energies. Our results show a novel, strong and positive correlation between $\Delta E_{PV}$ and $ECM$, supporting a subtle interplay between the weak-forces acting within the
nuclei of a given molecule and its chirality. These findings suggest that experimental investigations for molecular parity violation detection should consider molecules with as large $ECM$ values as possible, and may support that a
chiral signature is imprinted on life by fundamental physics via the parity-violating weak interactions.
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Materials Science
Defect dependent dynamic nanoindentation hardness of copper up to 25 000 s-1
Hendrik Holz, Lalith Kumar Bhaskar, Tobias Brink et al. (+4 more)
Metals exhibit an upturn in strength at strain rates of approximately 1000 s-1 - 3000 s-1, governed by rapid dislocation multiplication, interactions and storage. This phenomenon is strongly influenced by the initial dislocation density before testing. However, the role of immobile dislocations arranged in low-angle grain boundaries (LAGBs) on deformation under such extreme conditions remains unexplored, despite their ubiquity in engineering materials. Here, we employ high strain rate nanoindentation targeted at an LAGB with tilt and twist components in copper
crystals with different dislocation densities. We demonstrate that Taylor hardening remains valid over a wide range of strain rates. It was found that the influence of LAGBs on mechanical properties is within the scatter of the measurements. However, slip traces of indents close to the LAGB suggest that the LAGB acts as a barrier to dislocations. Molecular dynamics simulations further confirm these findings. The measured activation volume and low strain rate re-indentation onto indents performed at different higher strain rates give insights into the deformation mechanism. This work provides new insight into the interplay between microstructure and high strain rate deformation.
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All authors Hendrik Holz, Lalith Kumar Bhaskar, Tobias Brink, Dipali Sonowane, Gerhard Dehm, James P. Best, Rajaprakash Ramachandramoorthy
Materials Science · Cross-listed from quant-ph
Mapping g-factors and complex intervalley coupling in Si/SiGe by conveyor-mode shuttling
Mats Volmer, Tom Struck, Arnau Sala et al. (+7 more)
As silicon
spin qubit chips are increasing in
qubit number and area, methods for the screening of
qubit related material parameters become vital. Here we demonstrate the two-dimensional mapping of small variations of the electron g-factor of
quantum dots formed in planar Si/SiGe
quantum wells with precision better than $10^{-3}$ and with nanometer lateral resolution. We scan the electron g-factor across a 40 nm $\times$ 400 nm area and observe two g-factors per QD site which obey a striking
symmetry and bimodal distribution across the area. These two g-factors relate to valley states of the electron in the
quantum dot in agreement with a recent theoretical model. Using conveyor-belt shuttling of entangled electron
spin pairs, complementary to the mapping of the local valley-splitting, we map the g-factor. We compare g-factor and valley splitting maps measured on the same device, and extract the complex intervalley coupling parameter along the shuttle trajectories applying a theoretical model of g-factor dependence on intervalley coupling. These maps will allow unprecedented insights into the
spin-valley dynamics during
qubit manipulation, readout and shuttling and serve as a
benchmark for the engineering of Si/SiGe
heterostructures for large-scale
quantum chips.
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All authors Mats Volmer, Tom Struck, Arnau Sala, Jhih-Sian Tu, Stefan Trellenkamp, Davide Degli Esposti, Giordano Scappucci, Hendrik Bluhm, Łukasz Cywiński, Lars R. Schreiber
Materials Science
Probing Materials Knowledge in LLMs: From Latent Embeddings to Reliable Predictions
Vineeth Venugopal, Soroush Mahjoubi and Elsa Olivetti
Large
language models are increasingly applied to materials science, yet fundamental questions remain about their reliability and knowledge encoding. Evaluating 25 LLMs across four materials science tasks – over 200 base and fine-tuned configurations – we find that output modality fundamentally determines model behavior. For symbolic tasks, fine-tuning converges to consistent, verifiable answers with reduced response
entropy, while for numerical tasks, fine-tuning improves prediction accuracy but models remain inconsistent across repeated inference runs, limiting their reliability as quantitative predictors. For numerical regression, we find that better performance can be obtained by extracting
embeddings directly from intermediate
transformer layers than from model text output, revealing an “LLM head bottleneck,” though this effect is property- and
dataset-dependent. Finally, we present a longitudinal study of GPT model performance in materials science, tracking four models over 18 months and observing 9–43% performance variation that poses reproducibility challenges for scientific applications.
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Materials Science
Towards an understanding of magnesium in a biological environment: A density functional theory study
Miranda Naurin, Sally Aldhaim, Moltas Elliver et al. (+3 more)
Density functional theory is used to investigate the interactions between a layer of magnesium hydroxide, Mg(OH)2, the magnesium (Mg) surface Mg(0001), and the three amino acids glycine, proline and glutamine. The aim is to improve the understanding of Mg behavior in biologically relevant environments, such as the ones that biodegradable implants experience in the body. For a simple model of such conditions, adsorption of amino acids are studied. With the layer of Mg(OH)2 as a model of either slightly corroded Mg, or intentionally coated Mg, the interfacial interaction between a layer of Mg(OH)2 and Mg(0001) is first examined in the absence of the molecules. Then follows analyses that include amino acids on top of the Mg(OH)2 layer. We find that the Mg(OH)2/Mg(0001) interaction is weak and that the layer of Mg(OH)2 can readily slide across the Mg surface. The presence of amino acids is found to have a limited influence on the adsorption of Mg(OH)2 on Mg(0001), decreasing the binding by at most 3%, while more layers of Mg(OH)2 strengthen the Mg(OH)2/Mg(0001) binding by 13%. This is still less than the binding of Mg(OH)2 layers within its native bulk structure, and our findings indicate that only a small number of hydroxide layers are required before it is energetically more favorable for Mg(OH)2 to create bulk than to stay on Mg(0001) as single layers. This provides insight into early-stage surface processes relevant for magnesium-based implant materials.
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All authors Miranda Naurin, Sally Aldhaim, Moltas Elliver, Ludwig Hagby, J. Didrik Nilsson, Elsebeth Schröder
Materials Science
Time Resolved Study of Laser Induced Ultrafast Alloying Processes in Au/Pd Core Shell Nanorods
Abhisakh Sarma, Jayanath C. P. Koliyadu, Romain Letrun et al. (+16 more)
Femtosecond
laser-induced alloying presents a novel approach to modifying bimetallic systems. Visualizing ultrafast processes during
laser-induced alloying is essential to uncover fundamental mechanisms associated with phase transformations, which enables precise control over material composition and structure at the atomic level. In this study, we investigated the ultrafast dynamics of
laser-induced alloying of Au/Pd core-shell nanorods using a time-resolved X-ray diffraction technique at an X-ray free-electron
laser facility, capturing the structural
evolution from picoseconds to microsecond timescales. We found that a
laser fluence threshold of ~ 48 mJ/cm2 with 800 nm excitation is sufficient for melting and subsequent
alloy formation. Above this threshold, the formation of Au1.51Pd0.49 was observed, and we found that alloying is not a single-step phenomenon; instead, it is a dynamic process involving interdiffusion.
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All authors Abhisakh Sarma, Jayanath C. P. Koliyadu, Romain Letrun, Egor Sobolev, Trupthi Devaiah C, Agnieszka Wrona, Katerina Doerner, Diogo V. M. Melo, Marco Kloos, Huijong Han, Marcin Sikorski, Konstantin Kharitonov, Juncheng E, Joana Valerio, Pralay K. Santra, Erik M. J. Johansson, Richard Bean, Chan Kim, Tokushi Sato
Materials Science · Cross-listed from physics.chem-ph
Weiner's theory for exactly solvable Schrödinger equation with symmetric double well potential
A.E. Sitnitsky
The Weiner's theory (WT) is developed on the basis of the exactly solvable Schrödinger equation with trigonometric double-well potential (TDWP). The symmetric case of TDWP is considered. This modified version of WT (mWT) enables one to eliminate some severe approximations of the original Weiner's approach and to obtain more accurate results. An analytic formula is derived which provides the calculation of the
proton transfer rate with the help of elements implemented in {\sl {Mathematica}}. We exemplify the application of mWT by calculating the
proton transfer rate constant in the hydrogen bond of the
proton-bound ammonia dimer cation ${\rm{N_2H_7^{+}}}$ (${\rm{H_3N\cdot\cdot\cdot H^{+} \cdot\cdot\cdot NH_3}}$). The parameters of the model for this object are extracted from available literature data on IR spectroscopy and
quantum chemical calculations. The approach yields the transition from the Arrhenius-like exponential temperature dependence characteristic of thermal activation to that of
quantum tunneling. Besides it is well suited for describing the phenomenon of vibrationally enhanced tunnelling.
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Materials Science · Cross-listed from cond-mat.soft
Ostwald's Rule of Stages in One-Dimension
Jiajun Chen, Ying Xia, Mingyi Zhang et al. (+2 more)
Ostwald's Rule of Stages, which is one of the most widely observed phenomena associated with crystallization of polymorphs, follows naturally from the thermodynamics of nucleation. However, most observations of its manifestations have been limited to three-dimensional
crystals and its validity in one-dimension, where no nucleation barrier exists, remains unclear. Here we investigate the two-dimensional assemblies and phase transformation mechanisms of a peptide that forms two distinct phases on graphite via one-dimensional nucleation using in situ atomic force microscopy. We find that the
evolution of phases illustrates Ostwald's Rule, but does so for purely kinetic reasons, and that the stable phase replaces the metastable via a dissolution-reprecipitation mechanism enabled by inherent fluctuations of the phase boundary. The findings provide general insights into the growth and transformation mechanisms of coexisting two-dimensional phases and thus delineate a strategy for capturing transient two-dimensional structures.
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All authors Jiajun Chen, Ying Xia, Mingyi Zhang, Yu Huang, James J. De Yoreo
Materials Science
Percolation-driven $\beta$ -relaxation enables resonant acceleration of crystallization in amorphous phase-change materials
Yu-Yao Liu, Liang Gao, Jun-Ying Jiang et al. (+9 more)
Amorphous phase-change materials enable fast and reversible switching in optical and electronic devices, yet crystallization kinetics are still controlled primarily through empirical thermal protocols. Here we identify a microscopic picture governing crystallization in the prototypical phase-change material Ge2Sb2Te5, in which crystallization pathways are organized by the percolation of mobile atomic networks associated with $\beta$-relaxation. We show that this percolation transition distinguishes the dominance of
diffusion-driven and diffusionless nucleation and growth during crystallization processes. We further demonstrate that frequency-selected ultrasonic excitation, applied in conjunction with heating, accelerates crystallization by enhancing percolation-mediated atomic dynamics. This acceleration is maximized near the $\beta$-relaxation frequency, consistent with resonant excitation of mobile atoms. Our results establish a direct link between glassy relaxation, atomic-scale percolation, and crystallization, and introduce a new route to modulating phase-change kinetics through targeted excitation of fundamental glassy dynamics.
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All authors Yu-Yao Liu, Liang Gao, Jun-Ying Jiang, Yiming Zhou, Jan Luebben, Di Zhao, Xiaoling Lu, Maximilian J. Müller, Ulrich Boettger, Jiang-Jing Wang, Hai-Bin Yu, Shuai Wei
Materials Science · Cross-listed from math.AP
Testing Hooke-like isotropic hyper-/hypo-elastic material models under finite simple shear deformations
Sergey N. Korobeynikov, Alexey Yu. Larichkin and Patrizio Neff
We test some Hooke-like isotropic hyper-/hypo-elastic material models under finite simple shear deformations (cf., Thiel et al. Int. J. Non-linear Mech. 112: 57–72, 2019) and show that (1) the components of the Cauchy stress tensor for any Cauchy/Green isotropic elastic material under left finite simple shear (LFSS) deformation are equal to the components of the rotated Cauchy stress tensor for the same material under right finite simple shear (RFSS) deformation; (2) for any Hill's linear isotropic hyperelastic material model based on a symmetrically physical (SP) strain measure, LFSS and RFSS deformations lead to Eulerian and Lagrangian pure shear stresses, respectively; (3) for any two-power Ogden's isotropic hyperelastic material model based on a SP strain function, LFSS and RFSS deformations lead to Eulerian and Lagrangian pure shear stresses, respectively; (4) for some Hooke-like isotropic hypoelastic materials with constitutive relations based on corotational stress rates under LFSS deformation, the behavior of the Cauchy stress tensor components as a function of the shear parameter is qualitatively similar to that for the same materials under simple shear deformation. In addition, we confirm the results of Lin (Lin R.C. ZAMP, 75: 191, 2024) showing that for some Hooke-like isotropic hypoelastic materials with constitutive relations based on corotational stress rates without initial stresses under RFSS deformation, the Cauchy stress tensor components coincide with those for the Hencky isotropic hyperelastic material.
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Materials Science · Cross-listed from physics.comp-ph
On the Intrinsic Link between Gradient Strengthening and Passivation Onset in Single Crystal Plasticity
Habib Pouriayevali
A finite-deformation framework for gradient
crystal plasticity is developed within a thermodynamically consistent setting grounded in Gurtin's power-conjugate formulation. The model introduces a flow rule that accounts explicitly for both energetic and dissipative microstress contributions. Numerical simulations are performed to investigate the response of single
crystals subjected to passivation-type boundary constraints. The results reveal that constitutive laws capable of reproducing size-dependent strengthening at the onset of plastic flow simultaneously generate a pronounced, nearly elastic-type response when passivation is imposed. These findings establish a fundamental connection between gradient-induced yield strengthening and boundary-driven elevation of the mechanical response, highlighting the essential influence of dissipative gradient effects.
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Materials Science · Cross-listed from cond-mat.mes-hall
Insulating Electronic States Near the Dirac Point Arising from Twisted Stacking and Curvature in 3D Nanoporous Graphene
Yoichi Tanabe, Hayato Sueyoshi, Samuel Jeong et al. (+3 more)
Twist-stacked
graphene with a twist angle $\theta$ of $\sim 5^\circ$–$30^\circ$ retains two-dimensional monolayer
graphene-like Dirac states near the Dirac point. In three-dimensional nanoporous
graphene (3D-NPG),
curvature inherently produces twist-stacking and topological defects required to form a porous network. When regions with $\theta \ge 5^\circ$ dominate, Dirac states in individual layers are expected to persist, allowing the Dirac-electron behavior to be tuned through coupling to the 3D curved geometry. However, predicted band gap formation or localized states have remained unobserved. Here we report that 3D-NPG maintains monolayer-like Dirac electronic states while simultaneously exhibiting insulating behavior near the Dirac point. Raman G-band softening confirms these monolayer-like states, and an Arrhenius-type temperature-resistance trend coexisting with weak localization near the Dirac point indicates partially insulating states induced by topological defects. These findings demonstrate that 3D-NPG hosts distinctive Dirac electronic states coupled to 3D
curvature, providing a platform for developing new functionalities in 3D
graphene-based electronics and energy devices.
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All authors Yoichi Tanabe, Hayato Sueyoshi, Samuel Jeong, Kojiro Imai, Shojiro Kimura, Yoshikazu Ito
Materials Science
Pressure-induced lattice instabilities and phonon softening in the orthorhombically distorted ferrimagnet Ni4Nb2O9
Rajesh Jana, Xinyu Wang, Takeshi Nakagawa et al. (+4 more)
The ambient- and high-pressure behavior of the ferrimagnet Ni4Nb2O9 (orthorhombically distorted honeycomb structure), is investigated using NMR, Raman spectroscopy, and synchrotron XRD. Ambient-pressure NMR measurements reveal, despite its orthorhombic
symmetry, the local environment of Ni4Nb2O9 closely resembles that of its trigonal analogue Mn4Nb2O9. In contrast, substantially different paramagnetic shifts observed in the two compounds reflect their distinct average
crystal symmetries, governing orbital overlap and
magnetic exchange pathways. Under external pressure, Ni4Nb2O9 exhibits pronounced sensitivity to
lattice distortions and
phonon instabilities. Three isostructural transitions are identified near 2, 6, and 10 GPa, manifested by mode splitting, frequency shifts, line broadenings, intensity anomalies, and slope changes in the
evolution of
lattice parameters. At higher pressure, around 13 GPa, signatures of an incipient long-range structural transition from orthorhombic Pbcn to monoclinic P2/c
symmetry emerge, signaling the onset of a
symmetry-lowering transformation. The anomalous softening of the 192 cm^-1 Raman mode, accompanied by multiple linewidth and spectral-weight anomalies, serve as a key fingerprint of these structural instabilities, linking local
symmetry breaking at low pressures to the long-range transition into the P2/c phase. Notably, pronounced linewidth anomalies, strongly anisotropic pressure coefficients, together with a marked enhancement of the intensity of the low-frequency branch over the 2-13 GPa range, point toward a pressure-induced regime influenced by coupled
spin, orbital, and
lattice degrees of freedom. The close correspondence of transition pressures in Ni4Nb2O9 and those reported for Mn4Nb2O9 highlights a common mechanism rooted in their similar local structural environments, as revealed by NMR.
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All authors Rajesh Jana, Xinyu Wang, Takeshi Nakagawa, Hirofumi Ishii, Alka Garg, Rekha Rao, Thomas Meier
Materials Science · Cross-listed from physics.optics
Plasmonic- and Electronic-Enhancement-Free Coherent Raman Detection of Ångström-Scale Molecular Layers at Metal Interfaces
Toshiki Sugimoto, Tomoaki Ichii, Tsuneto Kanai et al. (+5 more)
Coherent Raman scattering provides highly sensitive vibrational analysis through nonlinear light-matter interactions. However, its application to metal interfaces has remained challenging because the intrinsically large non-resonant background (NRB) of metals overwhelms weak interfacial molecular vibrational signals, making direct Raman detection without plasmonic or electronic enhancement highly challenging. Here, we report a time-frequency hybrid coherent Raman spectroscopy approach that overcomes this limitation and enables sensitive detection of ångström-thick molecular systems even on atomically flat metal surfaces. Our method employs a time-frequency engineered detection scheme that combines femtosecond pump and Stokes pulses with a time-delayed, asymmetrically shaped picosecond probe pulse. By exploiting instantaneous temporal response of the metal NRB, this pulse configuration effectively filters out the dominant metal NRB in the time domain while retaining a controlled residual NRB that acts as an internal local oscillator, enabling strong interferometric amplification of weak interfacial vibrational signatures. This all-optical coherent enhancement strategy establishes a new route for direct, non-invasive Raman detection of interfacial molecular systems across a wide range of surfaces without requiring structure- and material-specific plasmonic and electronic enhancement mechanisms.
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All authors Toshiki Sugimoto, Tomoaki Ichii, Tsuneto Kanai, Ryu Yoshizawa, Shota Takahashi, Atsunori Sakurai, Keisuke Seto, Jin Chengxiang
Materials Science · Cross-listed from cond-mat.mes-hall
Valleytronics in 2D Materials Roadmap
Kyle L. Seyler, Giancarlo Soavi, Bent Weber et al. (+30 more)
Valleytronics exploits non-equivalent energy extrema in the electronic band structure of crystalline solids – the valley degree of freedom – to encode, manipulate, and read out information. The advent of 2D materials, first
graphene and then transition-metal dichalcogenides, made valley control practical through optical, electrical, and
magnetic routes. This foundation has enabled remarkable progress in recent years spanning established frontiers, such as valley
exciton physics and valley
Hall effects, as well as emerging directions including lightwave valleytronics, nanophotonic integration, flat-band valleytronics, and
spin-valley
qubits. In parallel, there are sustained efforts to scale up valleytronic materials and to predict new valleytronic platforms. This Roadmap brings together perspectives from leading experts to chart the key opportunities and challenges at the forefront of 2D material valleytronics. Each section captures a snapshot of progress in a key research area, identifies critical open challenges, and outlines pathways toward future valleytronics breakthroughs.
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All authors Kyle L. Seyler, Giancarlo Soavi, Bent Weber, Sunit Das, Amit Agarwal, Ioannis Paradisanos, Mikhail M. Glazov, Oleg Dogadov, Francesco Gucci, Giulio Cerullo, Stefano Dal Conte, Shubhadeep Biswas, Jan Wilhelm, Igor Žutić, Konstantin S. Denisov, Tong Zhou, Huiyuan Zheng, Wang Yao, Hongyi Yu, Ting Cao, Dacen Waters, Matthew Yankowitz, Guido Burkard, Artem Denisov, Thomas Ihn, Klaus Ensslin, Louis Gaudreau, Justin Boddison-Chouinard, Zlata Fedorova, Isabelle Staude, Kuan Eng Johnson Goh, Zhichao Zhou, Xiao Li
Materials Science
Designing a family of 2D kagome monolayer $B_{18}S_{8}$, $B_{18}S_{8}H_{2}$, $B_{18}S_{6}X_{2}$ (X=Cl,Br,I) with tunable Dirac cones and high Fermi velocity
Su-Yang Shen, En-Qi Bao, Xing-Yu Wang et al. (+2 more)
Two-dimensional (2D) kagome materials have become a hot research topic in the current scientific community due to their unique electronic structural properties, and the design of novel 2D kagome materials represents a significant exploration direction in this field. In this study, by employing the "1+3" design strategy, surface passivation and charge balance strategies, we successfully designed a novel family of 2D kagome material $B_{18}S_{8}$, $B_{18}S_{8}H_{2}$, $B_{18}S_{6}X_{2}$ (X=Cl,Br,I). Electronic structure analysis revealed that although $B_{18}S_{8}$ exhibits excellent kagome band characteristics, its Dirac cone is located approximately 1 eV above the
Fermi level, making it difficult to utilize. However, by surface hydrogen passivation, the Dirac cone can be effectively adjusted to the
Fermi level. Further research found that introducing halogen atoms to replace surface sulfur atoms can similarly adjust the position of the Dirac cone to the
Fermi level. The
Fermi velocities near the Dirac cone for these five materials reach as high as 2.69 to 3.07*$10^5$ m/s. Additionally,
spin-orbit coupling can open a bandgap of approximately 20 to 55 meV at the Dirac cone. Our research not only provides an outstanding example for the design of 2D boron-based kagome materials but also fully demonstrates the immense potential of such materials in the electronics field.
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All authors Su-Yang Shen, En-Qi Bao, Xing-Yu Wang, Jiafu Wang, Jun-Hui Yuan
Materials Science
Probing Coordination Environments in Buried Oxides of Aluminum Josephson Junctions by Resonant X-ray Reflectivity
Paul Corbae, Alex Abelson, Shivani Srivastava et al. (+16 more)
Decoherence remains a critical obstacle to achieving high-fidelity, scalable superconducting
qubits, with the tunnel barrier of Josephson junctions a key source of loss. Here we apply resonant X-ray reflectivity to non-destructively probe the electronic structure of buried layers in Al/AlO$_x$/Al Josephson junctions. At the Al $K$-edge, energy-dependent modulations in the reflectivity maps enable Kramers-Kronig-constrained extraction of the layer-resolved atomic scattering factors. The analysis reveals that the barrier coordination evolves from more tetrahedral toward predominantly octahedral character with increasing oxidation pressure. At the interfaces, the lower metal-
oxide boundary is comparatively under-coordinated and disordered relative to the upper interface. Comparison with simulated X-ray absorption spectra identifies the dominant coordination motifs within the
oxide and its interfaces, providing depth-resolved structural insight that constrains microscopic models of two-level system formation. These results link growth conditions, local coordination environments, and junction electronic properties, demonstrating resonant X-ray reflectivity as a powerful tool for probing the microscopic materials properties of Josephson junctions and providing a materials-level framework for mitigating decoherence in superconducting
qubits.
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All authors Paul Corbae, Alex Abelson, Shivani Srivastava, Heemin Lee, Bevin Huang, Lyrik R-J Lee, Davis B. Rash, Cheng-Tai Kuo, Donghui Lu, Mihir Pendharkar, Loren D. Alegria, Tian T. Li, Keith G. Ray, Shannon P. Harvey, Apurva Mehta, David I. Schuster, Vincenzo Lordi, Paul B. Welander, Jun-Sik Lee
Materials Science · Cross-listed from cond-mat.mes-hall
Learning-Performance Evaluation of a Physical Reservoir Based on a Vortex Spin-Torque Oscillator with a Modified Free Layer
Kota Horizumi, Takahiro Chiba and Takashi Komine
In this study, we numerically evaluate the learning performance of a
vortex spin-torque oscillator (VSTO) with a modified free layer, called a modified VSTO (m-VSTO), in which an additional layer (AL) of smaller radius is stacked on the free layer, for physical reservoir computing. The
vortex-core dynamics are computed using the Thiele equation incorporating the potential deformation induced by the AL. We identify the edge of chaos from the maximal Lyapunov exponent and quantify the short-term
memory capacity (STMC) as well as the information processing capacity (IPC) in a time-multiplexed reservoir scheme. We find that the m-VSTO exhibits finite STMC and IPC in a low-current and low-field regime below the threshold current of the conventional VSTO, and can achieve up to approximately twice the IPC with about one quarter of the power consumption. The pulse-width dependence of the IPC can be further interpreted by combining an analytical estimate of the transient time with Lyapunov-exponent data. Longer pulse widths promote stronger recovery-induced contraction toward the groove-trapped orbit over a wide range of subthreshold currents. In contrast, this difference in contraction rate becomes less pronounced near the threshold current, where the transient time increases rapidly. Consequently, the IPC is enhanced in a stable regime with a negative Lyapunov exponent rather than exactly at the edge of chaos. These results suggest that engineering the potential landscape and pulse-width-dependent recovery dynamics enables low-power spintronic physical reservoirs.
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Materials Science · Cross-listed from physics.comp-ph
Update of PHYSBO: Improving Usability and Portability of Bayesian Optimization for Physics and Materials Research
Yuichi Motoyama, Kazuyoshi Yoshimi, Tatsumi Aoyama et al. (+3 more)
Bayesian optimization (BO) is widely used to accelerate physics and materials research, where objective function evaluations are computationally or experimentally expensive. While many BO frameworks focus on algorithmic efficiency, practical usability and portability are equally critical for sustained use in real research environments. PHYSBO is a
Bayesian optimization library designed to address these needs by enabling optimization over user-defined candidate pools and by supporting domain-specific problem settings. This paper presents the major updates introduced in PHYSBO versions 2 and 3, with a focus on improvements in usability, portability, and practical deployment rather than on new optimization
algorithms. In PHYSBO version 2, the software license was changed from GPL to MPL to improve compatibility with a wider range of research and software ecosystems. Building on this revision, PHYSBO version 3 introduces a set of implementation-oriented updates aimed at improving usability and portability, without modifying the core optimization
algorithms. These updates include improvements in computational performance and scalability, extended support for multi-objective optimization, the introduction of range-based policies for continuous-variable optimization, the removal of environment-dependent components such as tightly coupled Cython modules, and compatibility with NumPy 2. These improvements reduce the technical and organizational burden on users, enabling PHYSBO to be deployed across diverse computing environments and research workflows. By emphasizing portability and ease of integration while maintaining sufficient performance, PHYSBO version 3 is positioned as a sustainable research infrastructure for
Bayesian optimization in physics and materials science.
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All authors Yuichi Motoyama, Kazuyoshi Yoshimi, Tatsumi Aoyama, Kei Terayama, Koji Tsuda, Ryo Tamura