Materials Science · Cross-listed from cs.CV
RAFT-DVC: Resolution-Aware Machine Learning-Based Digital Volume Correlation
Zixiang Tong, Lehu Bu and Jin Yang
Digital volume correlation (DVC) provides three-dimensional full-field displacement measurements from volumetric images, but how the internal resolution of a machine-learning-based DVC model affects accuracy and operating range remains poorly understood. Here, we present RAFT-DVC, a resolution-aware family of recurrent all-pairs field transforms (RAFT)-based DVC solvers with encoder downsampling factors s = 2, 4, and 8. Using a matched design, we find that the three solvers localize displacement to approximately 0.017 feature-grid voxel, giving an empirical raw-volume error scaling of approximately 0.017s voxel. The solvers exhibit complementary operating regimes governed jointly by displacement reach and volumetric-texture compatibility. Synthetic
benchmarks show that RAFT-DVC achieves errors of the same order as tuned classical DVC under fine-texture, small-to-moderate-displacement conditions and becomes competitive or advantageous under coarse-texture, large-displacement conditions. Frequency-swept tests quantify deformation spatial resolution, while tiled inference enables dense estimation on large volumes. Evaluation on confocal volumetric images acquired during indentation illustrates the importance of matching solver operating regime to deformation magnitude and image texture. Tests on micro-CT images of elastomeric foam, despite training only on particle-labeled synthetic data, provide evidence of cross-texture transfer. We also identify coordinate-order inconsistencies in three-dimensional RAFT correlation sampling and introduce a non-cubic impulse test to verify sampler geometry independently of network training. Correcting the sampler improves native-input accuracy and generalization to unseen volume dimensions. Together, these results establish RAFT-DVC as a fast, resolution-aware framework for dense DVC with characterized accuracy and operating regimes.
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Materials Science
Molecular spin qubits in a van der Waals bottle
Anna Champ, Eleanor Mackintosh, André Koch Liston et al. (+22 more)
Advancing
quantum information technologies requires
qubits whose coherence can be precisely engineered. Among the
qubit platforms in development, molecular
spin qubits (MSQs) stand out for their atomic scale tunability and chemical specificity, making them powerful candidates for sensing, simulation, and information processing. However, integrating MSQs into solid-state architectures without degrading their coherence remains a central challenge. Here, we introduce van der Waals (vdW) confinement within two-dimensional materials as a strategy for stabilizing
quantum states in MSQs by engineering their local electronic, vibrational, and
symmetry environments. Using cobaltocene as a model system, we show that confinement within vdW SnS2 and CdPS3 single
crystals reorganizes the single-ion energy landscape and slows
spin-
lattice relaxation by over two orders of magnitude relative to unconfined cobaltocene. The confined MSQs adopt deterministic orientations and self-assemble into ordered, atomically precise superlattices, establishing vdW confinement as a pathway for integrating MSQs into functional
quantum devices.
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All authors Anna Champ, Eleanor Mackintosh, André Koch Liston, Sanghyo Lee, Eric D. Walter, Raphaël P. Hermann, George Yumnam, Eric Seewald, Xuehao Wu, Willa Mihalyi-Koch, Augustin Braun, Johan van Tol, Tomas Orlando, Mykhaylo Ozerov, Byeongjun Gil, Myung-Geun Han, Yimei Zhu, Miyoung Kim, Abhay N. Pasupathy, Milan Delor, Michael L. Steigerwald, Timothy C. Berkelbach, Colin Nuckolls, Xavier Roy, Arun Ramanathan
Materials Science
Symmetry-selective nonrelativistic spin splitting in antiferromagnets driven by coherent phonons
Sangeeta Rajpurohit, Mohsen Yarmohammadi, Sheikh Rubaiat Ul Haque et al. (+3 more)
Nonrelativistic
spin splitting (NRSS) in antiferromagnets (AFMs) enables magnetization-free
spin polarization for ultrafast spintronics. Here, we demonstrate that coherent
phonons can dynamically induce and control NRSS in collinear AFMs. Excitation of $\Gamma$-point infrared-active
phonons lifts the
spin degeneracy of the ground state, while the residual sublattice-connecting
symmetries determine the momentum-space form of the induced splitting. Because the relevant infrared modes couple to orthogonal in-plane light polarizations, distinct
spin-split phases can be selectively activated by the polarization of the driving field. Using first-principles calculations for MnPS$_3$, we show that a mode that breaks all sublattice-connecting
symmetries induces an $s$-wave
spin-split state with $\Delta(\Gamma)\neq0$, whereas a
symmetry-distinct mode that preserves a sublattice-connecting mirror
symmetry generates a $d$-wave altermagnetic state with $\Delta(\Gamma)=0$. In both cases, the
spin splitting grows linearly with the
phonon amplitude and reverses the induced
spin polarization when the displacement is reversed. Our results establish coherent
lattice driving as a direct, polarization- and mode-selective route to dynamically induce distinct NRSS phases in AFMs.
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All authors Sangeeta Rajpurohit, Mohsen Yarmohammadi, Sheikh Rubaiat Ul Haque, Tony F. Heinz, Aaron M. Lindenberg, Tadashi Ogitsu
Materials Science
A Spatial Localizer for Constituent-Resolved Exciton Wannier Functions
Haylen Gerhard and Wladimir A. Benalcazar
Excitons are composite quasiparticles: beyond a center-of-mass position, each carries an internal electron-hole dipole governing its coupling to electric fields and other
excitons.
Exciton Wannier functions locally represent
exciton bands, but resolving this dipole requires localizing the electron and hole simultaneously. We show that, in one dimension, the projected electron and hole position operators fail to commute when the covariant derivative of the
quantum geometric dipole (QGD)
matrix (the difference between the hole and electron non-Abelian Berry connections) is nonzero. This precludes a common eigenbasis and bounds the joint electron-hole spread from below. For one band, the internal dipole is gauge invariant and center-of-mass methods suffice; for multiple bands, no existing construction yields a gauge minimizing both position uncertainties. We introduce an “
exciton spatial localizer,” a Hermitian operator
embedding both projected positions in a Clifford-
algebra structure. Its spectral minima locate the
exciton's center-of-mass and dipole coordinates, while its eigenvectors yield
exciton Wannier functions jointly localized in electron and hole coordinates without gauge fixing, an ansatz, or iterative optimization. In an interacting bilayer model, combined reflection–time-reversal
symmetry or a nonsymmorphic particle–hole
symmetry forces the QGD
matrix to be traceless at every momentum while allowing it to remain nonzero. A two-band
exciton subspace with zero net internal dipole then decomposes into a
symmetry-related pair of
exciton Wannier functions with opposite center-of-mass positions and internal dipoles. Adding the interlayer dipole as a Clifford component further separates intralayer and interlayer
exciton Wannier functions in a six-band subspace.
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Materials Science · Cross-listed from cond-mat.supr-con
Understanding the superconducting proximity effect in semiconductors through quantum oscillations
Milo Coombs, Teun A. J. van Schijndel, Yu Wu et al. (+5 more)
Superconductor-
semiconductor hybrids host emergent states of matter and offer a platform for new
qubits, but the superconducting metal shunts electrical transport, which rules out conventional
semiconductor characterization and leaves the hybrid parameters to speculation. Here we determine density, mass, $g$-factor, mobility and subband occupation beneath the
superconductor, from Shubnikov-de Haas oscillations of a buried InAs
quantum well under Al, Sn, V, Nb, Ta and Re films, with a Dingle analysis that accounts for the shunt. Every metal adds an interface subband whose occupation falls into one of two classes, whereas the mass and $g$-factor of the buried well are unchanged to within 10%. Within the uncertainty set by the transport mobility, no film shortens the
quantum lifetime of the buried well, and Al and Sn lengthen it.
Quantum lifetimes bound the hybridization of the interface subband to 2-4~meV. These measurements supply the normal-state parameters that tunnelling spectroscopy renormalizes but cannot measure.
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All authors Milo Coombs, Teun A. J. van Schijndel, Yu Wu, Jason T. Dong, Yilmaz Gul, Julian Choi, Christopher J. Palmstrøm, Greg P. Mazur
Materials Science
No source-free exchange-correlation magnetic fields in non-collinear spin-density functional theory
Ester Livshits and Roi Baer
The source-free condition, $\nabla\cdot\mathbf{B}_{xc}=0$, where $\mathbf{B}_{xc}$ is the exchange-correlation (xc)
magnetic field in non-collinear
spin-density functional theory, is widely believed to be exact. Recent studies report that when the field of a parent functional is made source-free by projection - a posteriori, rather than by construction - the predicted
magnetic moments improve. We show that the condition violates global
spin-rotation
symmetry of the xc energy functional $E_{xc}$ and therefore cannot be exact. It has nonetheless been found useful, so we examine the errors it introduces. We first implement the condition variationally, using any parent $E_{xc}$ functional: the resulting source-free (SoF) field is divergence-free, remains a functional derivative, and exerts local torques. With the LSDA as the parent functional, we examine Mn$_2$. SoF and the locally collinear (LoC) LSDA both give too short a bond and too large a bond energy, but they differ on the
magnetic and electronic properties: SoF finds the experimentally observed $^1\Sigma_g^+$ antiferromagnet, with a coupling of the right sign and, extrapolated to the experimental bond length, roughly the right size, while LoC finds a high-
spin $^{11}\Pi_u$ ferromagnet and the wrong sign. But breaking the
symmetry produces severe errors in every directional property. A rigid
spin rotation of the magnetization changes $E_{xc}$ by about 1 eV (it should not change at all); in a weak uniform external field the magnetization points perpendicular to the field (it should be antiparallel to it); and the system develops a spurious
magnetic anisotropy of about 175 meV (an effect that requires
spin-orbit coupling, which is absent here).
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Materials Science
First-principles optical response of shock-compressed LiF: Quasiparticle, excitonic, and ionic-temperature effects
M.S. Fadeev
We investigate the refractive index $n$ of LiF using DFT+G$_0$W$_0$+BSE, with ionic-temperature effects included through QMD. We calculate
photon-energy dispersions $n(\omega)$ and $k(\omega)$ at ambient pressure and $n(\rho,T)$ at 532 and 1550 nm under shock compression, where $\rho$ and $T$ vary together. Quasiparticle band structures at ambient and compressed conditions and the ambient-pressure orbital-projected density of states connect the optical response to the electronic structure. At ambient pressure, G$_0$W$_0$ yields a quasiparticle gap of 14.25 eV, close to the experimental 14.2 eV, while BSE reproduces the main excitonic feature at 12.5 eV, close to the observed 12.6 eV. Quasiparticle and excitonic effects are thus essential for accurate optical dispersion; the hybrid HSE functional does not reproduce the optical spectra. Along the principal Hugoniot up to 140 GPa, $n(\rho)$ agrees closely with shock data at 1550 nm and acceptably at 532 nm, and agrees better overall than earlier first-principles calculations. Above approximately 110-120 GPa, QMD produces a downturn relative to cold $n(\rho)$ curves, suggesting that ionic dynamics may contribute to deviations from the linear $n$-$\rho$ Gladstone-Dale relation. QMD-sampling and finite-k-grid uncertainties are estimated, and transition-peak broadening is assessed using a recently proposed criterion. The gap increases under pressure, with a transition to a $\Gamma\to\mathrm L$ indirect gap near 50 GPa. An exploratory calculation at approximately 1400 GPa finds a gap of about 24 eV, disfavoring gap-closure metallization. Structural and elastic
benchmarks of the underlying models are also provided.
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Materials Science
A relational fabrication-to-modeling database for memristor devices
Lai Gan, Guoyang Huang, Deepika Yadav et al. (+3 more)
Resistive random access
memory (RRAM) devices, also known as memristors, are highly dependent on fabrication, location on the wafer, and measurement protocols. However, openly available large-scale memristor
datasets remain scarce, particularly those that combine experimental metadata with electrical measurements and preserve explicit links across the experimental workflow. Here, we present a comprehensive relational database of automated electrical characterization data from oxide-based memristors. The database links 6,190 memristor devices across TiN/HfOx/TiN, Pt/TiOx/AlOy/Pt, and Pt/TiOx/Pt stacks to 161,006 validated experiments and over 169 million electrical point records. It integrates fabrication, wafer mapping, electrical characterization, and modeling to describe electroforming, current-voltage non-linearity,
memory windows (R_off/R_on), switching dynamics, and short-term
volatility. Released as a normalized and indexed SQLite database with schema documentation, graphical user interfaces, and examples of empirical modeling, this resource supports provenance-aware querying, statistical analysis, and data-driven applications for the development of future memristor technologies.
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All authors Lai Gan, Guoyang Huang, Deepika Yadav, Spyros Stathopoulos, Ben D. Rowlinson, Themis Prodromakis
Materials Science
Accelerating dynamic simulations of photoexcited materials and their evolution by electron-informed machine learning
Yunzhe Jia, Fankai Xie, Yunfei Bai et al. (+3 more)
Nonadiabatic coupled electron-nuclear dynamics upon electronic excitation underpin the microscopic mechanism and rational modulation of diverse photoinduced functional phenomena in materials, yet their direct first-principles simulations remain computationally demanding. Here we develop a framework for nonadiabatic excited-state machine-learning molecular dynamics (EMLMD) simulations, where the nonequilibrium electronic information upon photoexcitation such as electron temperature is rigorously calibrated from high-precision real-time time-dependent density functional theory (rt-TDDFT)
benchmark simulations, enabling accurate reconstruction of excited-state potential energy surfaces (PES). This framework natively incorporates the excited-state electron-
phonon couplings and intrinsically captures photoinduced
phonon anharmonicity, both of which are missing in standard machine learning molecular dynamics, thus delivering first-principles-level accuracy for excited-state atomic evolutions. Large-scale EMLMD simulations resolve time- and momentum-resolved
phonon dynamics in photoexcited materials, directly uncovering the competition between photogenerated coherent
phonons and thermal
phonons during photoinduced phase transition of bismuth. It also simultaneously resolves elusive atomic-scale microscopic dynamics and global structural rearrangement for selenium photoamorphization. Balancing high accuracy and efficiency, EMLMD offers a versatile paradigm to tackle key challenges in the study of complex excited-state molecular dynamics.
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All authors Yunzhe Jia, Fankai Xie, Yunfei Bai, Miao Liu, Cui Zhang, Sheng Meng
Materials Science
Polar nanoregions and reentrant-like ferroelectric behavior in SrTiO$_3$
Yuan-Jie Sun, Fei Yang and Long-Qing Chen
Recent real-space imaging in
quantum paraelectric SrTiO$_3$ [Nature 656, 54 (2026)] reveals that local polar textures do not continuously grow upon cooling, but reach a maximum intensity at intermediate temperatures around 60-65 K and weaken again toward the
quantum paraelectric ground state. Such a reentrant-like weakening of local polar textures challenges the conventional paradigm in which ordering tendencies generally continue to strengthen as temperature decreases. Here we employ a self-consistent phase-field theory showing that this anomalous behavior naturally arises from the coupling between intrinsic polar and antiferrodistortiv (AFD) fluctuations. We demonstrate that the flexoelectric-like coupling strongly hybridizes the polar and AFD modes. As the uncoupled polar and AFD modes cross near 52 K, their hybridization is maximized, driving the lower hybridized branch to develop a minimum on a finite-wave-vector shell. This finite-$q$ softening triggers a Brazovskii-type instability, strongly enhancing polarization correlations and producing nanoscale polar textures. Away from the crossing temperature, the two modes become increasingly detuned, weakening their hybridization and the associated finite-$q$ softening. These results reaveal the origin of the formation of polar nanoregions in SrTiO$_3$, naturally explaining the unexpected confinement to an intermediate-temperature window and providing a mechanism beyond the
quantum-fluctuation-based interpretation suggested by experiment. Furthermore, we predict an unconventional reentrant-like sequence in weakly strained SrTiO$_3$, evolving from ferroelectric to paraelectric, polar-nanoregion, and eventually paraelectric regimes upon heating from zero temperature.
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Materials Science · Cross-listed from physics.app-ph
Quasi-normal-mode signatures of periodicity and hyperuniformity
V. Romero-García, M. Martí-Sabaté, V. F. Dal Poggetto et al. (+2 more)
Hyperuniform materials occupy an intermediate regime between periodic order and conventional disorder, characterized by a suppression of long-wavelength density fluctuations, commonly quantified by the structure factor. This characterization, however, relies on the statistical properties of an extended configuration or supercell representation and does not directly describe the resonant response of a finite structure, as typically encountered in scattering experiments. Here, we introduce the quasi-normal-mode spectrum as a complementary framework for characterizing the wave properties of finite stealthy hyperuniform materials. We analyze the complex eigenfrequencies of both periodic and stealthy hyperuniform structures over a range of the stealthiness parameter ($\chi$), and investigate how the spatial organization of scatterers is encoded in both frequency and spatial profiles of their quasi-normal modes. We find systematic changes in the quasi-normal modes spectrum as the degree of hyperuniformity is varied, revealing signatures that are not captured solely by the structure factor. In particular, the
evolution of the resonant states provides a direct connection between structural correlations and the scattering response of finite systems. Our results establish quasi-normal modes as a real-space and open-system characterization of hyperuniformity and provide a unified framework for comparing discrete heterogeneous materials from the perspective of their scattering and resonant dynamics.
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All authors V. Romero-García, M. Martí-Sabaté, V. F. Dal Poggetto, L.M. García-Raffi, M. Lázaro
Materials Science
Simulating Continuous-Rotation 3D Electron Diffraction: A Multislice and Bloch Wave Framework
Małgorzata K. Cabaj, Jacob Madsen, Toma Susi et al. (+2 more)
To improve the agreement between measured and calculated intensities of three-dimensional electron diffraction (3D ED) experiments, a simulation pipeline is needed to assess and quantify the influence of various structural and experimental parameters. We present a computational pipeline, built upon the abTEM Python package, to simulate continuous-rotation 3D electron diffraction data based on either the Bloch wave or the multislice formalism. Multislice calculations in arbitrary orientations are achieved through large supercells and windowing. We investigate the convergence of key simulation parameters and test their consistency, establishing suitable parameters for accurate and efficient simulations. The pipeline's applicability and robustness are demonstrated through case studies on cubic silicon as well as stretched and sheared variants, analyzing the influence of electron kinetic energy, sample thickness, orientation, and
symmetry on simulated diffraction intensities. Finally, we investigate a representative selection of seven compounds, including cubic $\mathrm{SrTiO_3}$, monoclinic $\alpha$-glycine $\mathrm{C_2H_5NO_2}$, and triclinic kyanite $\mathrm{Al_2SiO_5}$ to validate the method. This framework for the simulation of 3D electron diffraction data establishes an approach to investigate the dependence of diffracted intensities on experimentally relevant parameters which are difficult to systematically investigate in experiments.
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All authors Małgorzata K. Cabaj, Jacob Madsen, Toma Susi, Lukáš Palatinus, Paul B. Klar
Materials Science
Thickness-Dependent Orbital-to-Spin Torque Signatures in Cr/Gd/Co Thin Films
Tiago de Oliveira Schneider, Michel Heidkamp, Luana Caron et al. (+5 more)
We studied orbital-torque generation in Cr(10nm)/Gd($t_{\mathrm{Gd}}$)/Co(3nm)/TaO$_x$ and the inverted stack Co(3nm)/Gd($t_{\mathrm{Gd}}$)/Cr(10nm) with $t_{\mathrm{Gd}}$ from 0 to $5\,\mathrm{nm}$ by combining electrical harmonic Hall measurements with magnetometry. A detailed understanding of the magnetometric data is obtained by cross-sectional chemical composition mapping. The data show temperature-dependent
magnetic compensation points, while elemental analysis provides evidence of pronounced intermixing, in particular of Gd and Co layers. From the harmonic Hall
dataset we extract the damping-like (DL) and field-like (FL) torque efficiencies normalized to the applied electric field, $\xi_{\mathrm{DL}}^{E}$ and $\xi_{\mathrm{FL}}^{E}$, and interpret their dependence on the Gd interlayer thickness using two different descriptions: (i) a naive-layer model and (ii) an
alloy model that accounts for interfacial mixing. Notably, upon reversing the stack order, the FL contribution changes sign, whereas the DL contribution does not change sign within the harmonic Hall measurements.
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All authors Tiago de Oliveira Schneider, Michel Heidkamp, Luana Caron, Inga Ennen, Matthias Opel, Alexey Arzumanov, Lambert Alff, Markus Meinert
Materials Science
Geometry-Controlled Magnetic and Electronic Landscapes in Anisotropic van der Waals Materials
Maciej Śmiertka, Ewelina Cybula, Oliwia Janikowska et al. (+10 more)
Electronic structure in van der Waals materials is commonly engineered through composition, strain, electrostatic gating and
heterostructure assembly. Here we introduce geometronics, a concept in which substrate geometry locally reorients an anisotropic
crystal, transforming homogeneous external perturbation into programmable
magnetic and electronic landscapes. We demonstrate this concept using a bilayer of the antiferromagnetic
semiconductor CrSBr transferred onto an inverted pyramidal nanoindentation, where the local
crystal orientation with respect to the external
magnetic field drives the coexistence of antiferromagnetic and ferromagnetic phases within a single continuous
crystal. The resulting
magnetic landscape creates a switchable excitonic potential well of up to 10–12 meV, directly visualised by spatially resolved spectroscopy. More generally, geometronics provides a universal route for deterministically programmed electronic and
magnetic landscapes without modifying the material itself. It therefore establishes substrate topography as a new design principle that exploits the intrinsic anisotropy of layered van der Waals materials.
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All authors Maciej Śmiertka, Ewelina Cybula, Oliwia Janikowska, Bartosz Hołyński, Gayatri, Grzegorz Krasucki, Mariusz Hasiak, Kseniia Mosina, Zdenek Sofer, Adam Babiński, Maciej R Molas, Paulina Plochocka, Michał Baranowski
Materials Science · Cross-listed from cond-mat.supr-con
Thermodynamics of $T_{\rm c}$ suppression in far-overdoped Tl$_2$Ba$_2$CuO$_6$
Ayanesh Maiti, David M. Broun, Seunghyun Khim et al. (+7 more)
The physical origin of the suppression of superconductivity with hole doping in overdoped cuprates remains unclear. We measure the electronic specific heat of microgram-scale Tl$_2$Ba$_2$CuO$_6$
crystals and find sharp superconducting anomalies persisting far into the overdoped regime. A weak-coupling BCS-like framework incorporating the known Fermi surface and cation disorder quantitatively reproduces the observed anomalies for $T_{\rm c}=14$-$25$ K and their weak doping dependence. The results show $T_{\rm c}(p)$ to be driven predominantly by a smoothly decreasing pairing strength.
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All authors Ayanesh Maiti, David M. Broun, Seunghyun Khim, Michal Moravec, Antony Carrington, Carsten Putzke, Vivek Mishra, Peter Hirschfeld, Andrew P. Mackenzie, Andreas W. Rost
Materials Science
Autonomous discovery of new structure-plausibility laws for explainable and rapid crystal diagnosis and screening
Zhilong Song and Lixue Cheng
Crystal generators and tool-using
agents propose structures faster than density functional theory (DFT) energy and
phonon calculations or experiments can assess them. Deciding which candidates merit expensive assessment is therefore the bottleneck, yet most screens test little beyond atomic overlap and give no chemical reason for failure. Here, our
agents generate, test and actively refute two million candidate laws, leaving eight Plausibility Rules for Inorganic Structures (PRIS). These laws encode five mechanisms: short-range repulsion, ionic contact and packing, electrostatic balance, bond-valence conservation and crystallographic site complexity. Experimental structures satisfy our law sets at 82–99%, but satisfy Pauling's rules 2–5 together at only 6.5%. The strictest set detects 87.9% of damaged
crystal structures, whereas distance cutoffs detect only 1.6–3.2%. PRIS plausibility is linearly correlated with synthesizability, so the PRIS-derived synthesis score (PSS) explainably screens 83.7% of hard-to-synthesize structures while retaining 80.7% of experimental structures. In a property-conditioned inverse-design run, PRIS and PSS can reduce the DFT validation queue by up to 67.3% and keep 99.2% of the candidates whose DFT-validated bulk moduli reach the design target. Beyond screening, PRIS explains why GNoME remains enriched in rare low-
symmetry structures and reveals how wrong-element assignments in falsified
crystal reports hide behind plausible coordinates. PRIS moves screening from a pass-or-fail verdict to a chemical reason for failure, showing that autonomous
agents can discover, by active refutation, physicochemical laws that guide calculations and experiments.
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Materials Science · Cross-listed from cond-mat.mes-hall
Probing Nonlinear Interactions of Dipolar Interlayer Excitons in MoSe$_2$/WSe$_2$ Heterobilayers
Sai Shradha, Luc F. Oswald, Md Tarik Hossain et al. (+10 more)
Interlayer
excitons in transition-metal dichalcogenide heterobilayers possess intrinsic out-of-plane dipole moments, providing a platform for investigating
exciton-
exciton interactions at high densities. Here, we use excitation-energy-dependent photoluminescence excitation (PLE) spectroscopy to probe the nonlinear response of dipolar interlayer
excitons in chemical vapor deposition-grown MoSe$_2$/WSe$_2$ heterobilayers. By tuning the excitation energy across intralayer
exciton resonances at fixed excitation power, we selectively vary the population injected into the interlayer
exciton states. Resonant excitation drives the system into a nonlinear regime, leading to saturation of the interlayer
exciton photoluminescence and an apparent broadening of the intralayer $1s$ resonances in the PLE spectra. At the same time, the interlayer
exciton emission exhibits a pronounced blueshift, reaching approximately 2.5 meV at 4 K and 1 meV at 75 K. The blueshift increases systematically with the interlayer
exciton population and is consistent with a net repulsive
exciton-
exciton interaction, with contributions from dipole-dipole repulsion in the density regime investigated. Our results establish PLE as a sensitive approach for accessing the nonlinear, high-density regime of interlayer
excitons and probing their interactions in van der Waals
heterostructures.
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All authors Sai Shradha, Luc F. Oswald, Md Tarik Hossain, Lukas Krelle, Nicole Engel, Axel Printschler, Julian Führer, Honey Jayeshkumar Shah, Daria I. Markina, Kenji Watanabe, Takashi Taniguchi, Andrey Turchanin, Bernhard Urbaszek
Materials Science
Pressure-regulated mechanochemistry at lithium metal-sulfide electrolyte interfaces
Kunik Jang, Jaehwan Choi, Jang Wook Choi et al. (+1 more)
Stack pressure is commonly treated as a means of maintaining physical contact in all-solid-state lithium-metal batteries, but it can also alter the chemistry of reactive solid-solid interfaces. Here, using pressure-aware, charge-resolved machine-learning molecular dynamics validated against DFT, we determine how pressure magnitude and loading geometry regulate interphase formation at Li||Li6PS5Cl interfaces. The response is nonmonotonic: compression at 1 kbar accelerates PS4 decomposition and Li2S-like ordering, whereas 10-100 kbar compression restricts structural rearrangement and long-range crystallization. Charge-resolved dynamics further identify sulfur-centered, lithium-rich early-interphase environments associated with subsequent Li2S-like ordering. Uniaxial loading accelerates interfacial reaction relative to isostatic loading at the same nominal pressure. Pressure also changes void closure and dead-lithium spreading in a defect-location-dependent manner. These results establish applied pressure as a mechanochemical process variable coupling interphase chemistry, ion transport and defect
evolution, providing a mechanistic framework for interpreting pressure effects in sulfide solid-state batteries.
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All authors Kunik Jang, Jaehwan Choi, Jang Wook Choi, Yousung Jung
Materials Science
Trap Dynamics and Conductivity Changes in AlGaN/GaN Heterostructures Under Ultrasonic Loading
Vladyslav Kaliuzhnyi, Mykola Tymochko, Oleksandr Gudymenko et al. (+2 more)
AlGaN/GaN
heterostructures are critical for high-power electronic devices but suffer from electron trapping at defects, limiting reliability. We investigate how ultrasonic vibrations affect electron transport in MOCVD-grown AlGaN/GaN
heterostructures by combining temperature-dependent Hall effect and high-resolution X-ray diffraction measurements. Here we demonstrate that ultrasonic loading induces persistent acoustoconductivity and
lattice parameter changes, attributed to acoustically driven rearrangement of metastable DX centers. This leads to increased carrier concentration and decreased mobility, reflecting defect state modulation by acoustic strain. These findings provide new insights into trap dynamics under dynamic deformation and suggest ultrasonic treatment as a potential approach to mitigate trapping effects, thereby enhancing the performance and reliability of GaN-based devices.
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All authors Vladyslav Kaliuzhnyi, Mykola Tymochko, Oleksandr Gudymenko, Oleg Olikh, Alexander Belyaev
Materials Science
Text-guided flow matching enables sample-efficient crystal structure generation
Wentao Li
Crystal generators can now propose periodic structures, but their control interfaces remain poorly matched to the mixed descriptors used in materials design. Text provides a compact way to combine composition,
symmetry, prototype and property cues, yet it has not been clear whether such information can steer flow-based
crystal generation. Here we introduce TFMat, a text-conditioned flow-matching framework that uses structured materials
language as a semantic prior for a CrystalFlow generator. Across Perov-5, Carbon-24 and MP-20
crystal structure prediction
benchmarks, TFMat improves one-candidate match rates over CrystalFlow and reaches a 92.04% MP-20 match rate with 20 candidates; in de novo generation, it improves element-count and density distribution
alignment while retaining coarse property consistency in composition-selected outputs. These results position structured text as an inspectable control layer for translating human-readable materials intent into candidate
crystals for downstream simulation and validation.
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Materials Science
Exchange striction determines how fast antiferromagnetic insulators demagnetize
Aleksandr Buzdakov, Ravi Kaushik, Nikolai Khokhlov et al. (+2 more)
Antiferromagnets combine terahertz
spin dynamics with insensitivity to stray fields, and how quickly their order can be manipulated sets the speed limit on device operation. Femtosecond optical pulses demagnetize antiferromagnetic
insulators on timescales that span picoseconds to nanoseconds across compounds, and no material parameter is known that accounts for the spread or predicts where a new compound will fall. In a compensated antiferromagnet, no angular momentum needs to leave the
spin system, so the rate is set by energy flow from the
lattice into the
spins. Time-resolved second-harmonic generation experiments show that Cr2O3 demagnetizes within 2 ps once the
lattice is driven above the Neel temperature, two orders of magnitude faster than the structurally similar FeBO3. First-principles calculations trace the disparity to exchange striction: short Cr-Cr contacts make the exchange coupling tenfold more sensitive to atomic displacements and widen the phase space for
phonon decay into
magnon pairs.
Spin-
lattice simulations with ab initio parameters reproduce the order of magnitude of the measured ratio. The derivative of the exchange coupling with respect to the ionic displacement thus emerges as a computable parameter that predicts how fast an insulating antiferromagnet can be demagnetized. The results advance our understanding of ultrafast control in insulating antiferromagnets, and suggest a practical pathway to screen candidate materials for thermally assisted antiferromagnetic
memory before synthesis.
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All authors Aleksandr Buzdakov, Ravi Kaushik, Nikolai Khokhlov, Sergey Artyukhin, Alexey Kimel
Materials Science
First-Principles Electronic Structure Calculation of Crystals in Laboratory Magnetic Fields
Sichao Wang, Chengye Lü, Xingao Gong et al. (+2 more)
External
magnetic fields can qualitatively reshape the electronic structure of
crystals, underpinning
quantum Hall physics, Landau-level spectra and field-induced topological phases. Their first-principles treatment at laboratory-scale fields is, however, hindered by
magnetic-flux quantization, which requires
magnetic unit
cells with areas inversely proportional to the applied field. Such
cells contain a large number of chemical unit
cells, rendering real-space and plane-wave calculations prohibitively expensive. Here we, for the first time, construct a
magnetic Bloch basis built from linear combinations of gauge-including Gaussian-type atomic orbitals, which incorporate the
magnetic-field phase factors required by
magnetic translation
symmetry. The framework requires far fewer basis functions than real-space or plane-wave representations of the same
magnetic supercell and retains the sparsity of an atom-centred basis, together substantially reducing computational cost. We validate the framework by reproducing Landau-level spectrum of
graphene from first principles. This approach provides a practical route to simulations of crystalline materials under experimentally accessible
magnetic fields.
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All authors Sichao Wang, Chengye Lü, Xingao Gong, Yingwei Chen, Hongjun Xiang
Materials Science · Cross-listed from cond-mat.soft
Mass-conserving growth percolation in polymer gelation
Ameya Rege and Lorenz Ratke
Polymer gelation involves the emergence of a system-spanning network from growing
polymer-rich domains, yet conventional percolation models typically prescribe particle size independently of material consumption. We formulate gelation as a locally mass-conserving growth-percolation process in which Voronoi capture zones define finite material reservoirs for individual
nuclei. Local depletion determines the evolving supersaturation and limiting particle size, while particle contacts generate a dynamic network whose first spanning cluster defines the gel point. Three mechanisms, namely, interface-,
diffusion-, and
polymer-blob-controlled growth produce distinct gelation kinetics while sharing the same accessible final state. Spatial fluctuations in nucleation further generate a distribution of gelation times. The framework separates gelation from saturation and naturally captures post-gel aging as continued growth and topological maturation.
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Materials Science
Numerical study of the grain-growth-induced non-parabolic kinetics of a solid-state reaction
Ya. A. Nikiforov, S. A. Chizhik and N. I. Baklanova
Non-parabolic growth of reaction layers is frequently observed in solid-state
diffusion couples, but the relationship between microstructural
evolution and the resulting kinetics remains incompletely understood. This effect is commonly attributed to grain growth, which can progressively reduce the contribution of fast grain-boundary
diffusion, causing the effective diffusivity of a polycrystalline product layer to evolve during reaction. This work develops a moving-boundary
diffusion model to describe product-layer growth while accounting for the local grain-growth history of the continuously formed product, as well as both bulk and grain-boundary
diffusion. Numerical simulations show that the reaction can pass through three distinct kinetic regimes: an initial approximately parabolic regime dominated by grain-boundary
diffusion, a transient sub-parabolic regime associated with strong spatial variation of the effective diffusivity, and a subsequent approximately parabolic regime dominated by bulk
diffusion. The magnitude and duration of the sub-parabolic regime depend on the relative grain-boundary and bulk diffusivities and on the kinetics of grain growth. The instantaneous growth exponent therefore evolves continuously and does not represent a unique kinetic constant. Nevertheless, fitting simulated layer-thickness data over finite experimental time intervals produces well-defined apparent exponents, demonstrating how a transient process can appear to obey a single power law.
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Materials Science
Weisfeiler-Lehman subtree encoding for Bayesian optimization of atomic configurations
Akira Kusaba, Tatoshi Yonemori, Tetsuji Kuboyama et al. (+1 more)
The efficiency of
Bayesian optimization (BO) of atomic configurations depends strongly on how configurations are encoded. We introduce the Weisfeiler-Lehman (WL) subtree kernel, which views configurations as element-labeled graphs and measures their similarity by how many local structural patterns they share, into
Bayesian-optimization-based configuration search. Because this kernel is reproduced as the plain inner product of explicit features (L$^2$-normalized histograms of local topological patterns), introducing it reduces to introducing the corresponding features: the encoding enters existing BO frameworks as an ordinary descriptor. In a
benchmark ground-state configuration search of cubic BC$_2$N evaluated with a universal machine-learning interatomic potential, the WL encoding reached the ground state almost immediately after a shared random initialization of 100 samples in every one of five independent rounds (108$\pm$5 evaluations on average), whereas the one-hot baseline required 280$\pm$122 evaluations; the WL-driven sampler first exhausted the degenerate ground-state group and then discovered the metastable degenerate groups from the bottom up, in order of increasing energy.
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All authors Akira Kusaba, Tatoshi Yonemori, Tetsuji Kuboyama, Yoshihiro Kangawa
Materials Science
Beyond Panchromatic Absorption: Deciphering the Excited-State Maze from Light Absorption to Photocatalysis in Dye-Sensitized MOFs
Manuela L. Kim, Mauricio E. Calvo, Katsuya Teshima et al. (+2 more)
Metal–organic frameworks (MOFs) are promising photocatalysts whose visible-light absorption can be extended through linker functionalization; however, a red-shifted absorption edge does not guarantee enhanced efficiency. Here, we establish a multi-spectroscopic framework to decipher the photophysical fate of photoexcited states in diazo-sensitized UiO-66 using 2D photoluminescence (PL/PLE) mapping and wavelength-resolved continuous-wave X-band photo-EPR. By correlating visible absorption with photo-EPR and PLE action spectra, we distinguish a productive red shift from a non-productive emissive red shift. In highly active UiO-66-Anisole (97% activity relative to \ch{TiO2}), photo-EPR tracks the new absorption band, confirming that excitation populates a charge-transfer pathway yielding persistent,
spin-separated states. Conversely, poorly active UiO-66-$\beta$-naphthol (4%) exhibits an extended visible absorption tracked by PLE but not photo-EPR. This reflects excitation trapping in a localized state caused by an ortho-$\mathrm{OH}$ group forming a rigid intramolecular hydrogen bond, which locks the keto-hydrazone tautomer and disrupts the conjugated azo bridge. A new optical overlap descriptor ($S_{\mathrm{Exc}}$) quantitatively captures this trade-off across the series. We demonstrate that photosensitizer design must suppress rigid tautomeric traps and target specific charge-transfer
manifolds ($\lambda \le 500$~nm) rather than merely maximizing apparent panchromatic absorption breadth.
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All authors Manuela L. Kim, Mauricio E. Calvo, Katsuya Teshima, Fabio La Mattina, Eugenio H. Otal
Materials Science
Element priors and target support shape chemical transfer in materials graph networks
Ran Zhao and Kangming Li
Materials graph neural networks must often transfer to chemical regions weakly represented in training data. Such transfer can rely on predefined relations among elements or supervised evidence from target-containing structures, but these pathways are usually entangled. Here, held-out-element splits and incremental target support separate their roles. Without target-containing training structures, formation-energy errors depend strongly on the element representation, particularly for H, O and F. Matched perturbations show that representation-induced sharing matters beyond input dimension or numerical form, while a label-free similarity-graph prior reduces selected zero-shot errors. Adding a few target-containing structures sharply lowers errors and contracts differences among one-hot, k-hot and continuous inputs across ALIGNN and CGCNN. Calibration explains only part of this recovery, and freezing the initial element projection preserves most gains in five of six ALIGNN splits. Target support therefore shifts chemical transfer from reliance on static element relations toward learning from target-containing environments.
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Materials Science
Fourier Neural Operators for Composition-Driven Crystal Structure Discovery
Zhijie Yu, Jingyu Li, Yang Huang et al. (+1 more)
Crystalline materials discovery is essential for energy, electronics, and catalysis, but the vast chemical and structural space makes exhaustive screening infeasible. Existing voxel-based methods are limited by the local receptive fields of three-dimensional convolutional neural networks and the posterior collapse of high-dimensional variational autoencoders. Here, we develop a
Fourier Neural Operator (FNO)-based
crystal-field solver that maps a prescribed chemical formula and
lattice parameters to periodic number-density and electron-density fields. By operating on global
Fourier modes, the solver captures long-range correlations in periodic
crystal fields beyond conventional local convolutions. Building on this solver, we construct a coupled generation-solving framework in which a conditional variational autoencoder generates diverse candidate
lattice parameters in a low-dimensional basis-coefficient space, followed by density-field prediction and atomic reconstruction through peak detection, position optimization, and weight optimization. The reconstructed structures are further screened using voxel-level filtering, machine-learning interatomic-potential relaxation, and first-principle calculations. The framework generates novel structures across 104 chemical formulas with competitive reconstruction accuracy, demonstrating high generative diversity and structural validity. By extending
Fourier neural operators to periodic
crystal fields and coupling them with composition-conditioned
lattice generation, our approach provides a scalable route to
crystal structure discovery from prescribed chemical compositions.
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All authors Zhijie Yu, Jingyu Li, Yang Huang, Jingrun Chen
Materials Science
Large Exchange Magnetostriction in a Kagome Antiferromagnet at Room Temperature
Jie Du, Liang Yao, Hang Li et al. (+5 more)
The pursuit of high-performance magnetostrictive materials is crucial for advancing technologies in sensing, actuation, and microelectromechanical systems. Although pronounced magnetostrictive effects have been observed in a few ferromagnets, a systematic exploration of magnetostriction across a broader range of antiferromagnets remains limited. Here, we report the observation of large magnetostriction in the kagome antiferromagnet YMn6Sn6. Under a
magnetic field, the system undergoes a field-induced
evolution from a helical
magnetic ground state toward a collinear field-polarized state, accompanied by a large anisotropic
lattice strain and a substantial volume magnetostriction exceeding 400 ppm at room temperature. Remarkably, the magnetostrictive response remains nearly fully reversible up to 9 T with nearly hysteresis-free behavior, effectively minimizing the energy dissipation commonly associated with domain-wall pinning. Combined experimental measurements and theoretical calculations reveal that the large, nearly hysteresis-free magnetostriction originates from the competition between intralayer ferromagnetic and interlayer exchange interactions. This exchange-driven magnetoelastic coupling further gives rise to a strongly direction-dependent
lattice distortion pathway. This work establishes kagome helimagnets as a tunable platform for low-dissipation magnetoelastic functionalities and responsive magnetomechanical applications.
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All authors Jie Du, Liang Yao, Hang Li, Xiaodong Zhou, Yuan Yao, Xuekui Xi, Yong-Chang Lau, Wenhong Wang
Materials Science
Independent Tuning of Surface Acoustic-Waves and Spin-Waves via Buffer-Layer Engineering in Co2FeGe Heusler Thin Films
A. V. Achuthan, A. Vovk, S. Bunyaev et al. (+7 more)
Understanding and controlling acoustic and
spin-wave excitations in
magnetic thin films is critical for the development of magnonic and
spin-acoustic devices. We report on the use of Cr and W buffer layers to independently modify the acoustic and
magnetic excitations in Co2FeGe full-Heusler thin films grown on MgO(001). Using Brillouin light scattering (BLS) spectroscopy and ferromagnetic resonance (FMR), we probed Rayleigh and Sezawa surface acoustic waves (SAWs) alongside Damon-Eshbach and perpendicular standing
spin-wave (PSSW) modes. Our results show that acoustic dispersion depends strongly on the buffer material; W-buffered films exhibit a pronounced 16% reduction in Rayleigh SAW frequency compared to buffer-free films, primarily due to mass loading and acoustic impedance shifts. While the buffer layers significantly shift acoustic frequencies, they simultaneously modify the dynamic
magnetic response (increasing
spin-wave group velocity by ~34%) through different physical mechanisms. Finite-element simulations show excellent agreement with the experimental acoustic data. These findings demonstrate that buffer-layer engineering is an effective strategy for the independent tailoring of elastic and
magnetic excitations, providing a versatile platform for hybrid
spin-acoustic technologies.
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All authors A. V. Achuthan, A. Vovk, S. Bunyaev, B. Postolnyi, P. Štrichovanec, P. A. Algarabel, K. Załęski, J. P. Araujo, G. N. Kakazei, A. Trzaskowska