Materials Science
Engineering Excitons through Polymorphism and Dimensional Confinement in Low-Dimensional Tellurium
Gabriel Elyas Gama Araujo, Alexandre Cavalheiro Dias and Andreia Luisa da Rosa
The interplay between dimensionality, band-edge electronic structure, and electron-hole interactions governs the optical response of low-dimensional tellurium, yet the microscopic origin of its excitonic behavior remains largely unexplored. Here, we investigate the quasiparticle, excitonic, and optical properties of two-dimensional tellurium polymorphs and one-dimensional helical nanowires using many-body GW and the Bethe–Salpeter equation. Our results reveal a strong dependence of the excitonic response on band-edge dispersion,
crystal symmetry, and dimensional confinement. $\alpha$-tellurene exhibits comparatively weak and spatially extended electron-hole correlations, whereas the SOC-induced quasi-flat band-edge states of $\beta$-tellurene give rise to a strongly bound and anisotropic near-infrared
exciton. Momentum-resolved BSE eigenvectors and real-space
exciton wave functions directly reveal the contrasting localization and anisotropy of these excitonic states. Remarkably, hydrogen-passivated hexagonal tellurene, previously identified as a
quantum spin Hall phase with $Z_2=1$, supports an even larger direct
exciton binding energy of 0.51 eV together with a compact and nearly isotropic in-plane excitonic distribution. This demonstrates that strong electron-hole correlations are fully compatible with nontrivial band
topology, while the binding strength and spatial character of the
exciton remain strongly dependent on the underlying band-edge electronic structure and
crystal symmetry. The one-dimensional helical nanowire represents the strong-confinement limit, exhibiting a direct high
exciton binding energy and a pronounced shift of the optical response toward the ultraviolet.
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Materials Science
Benchtop Momentum-Resolved Phonon Spectroscopy: Unlocking Lattice Dynamics via X-ray Diffuse Scattering
Paulo H. V. da Silva, Tarsis M. Germano, Rafaela F. S. Penacchio et al. (+1 more)
Momentum-resolved
phonon spectroscopy is essential for understanding the thermal, electronic, and structural properties of materials, yet it traditionally necessitates access to large-scale synchrotron or
neutron facilities. We report a paradigm shift by demonstrating the accurate measurement and quantitative analysis of Thermal Diffuse Scattering (TDS) patterns using a commercially available benchtop Small/Wide-Angle X-ray Scattering (SAXS/WAXS) instrument. By utilizing a low-energy (8 keV) X-ray source and a custom-integrated
vacuum geometry, we acquired characteristic TDS patterns in silicon (111) and (100) slabs. We demonstrate that these benchtop images contain sufficient information to extract interatomic force constants (IFCs) through global optimization
algorithms, achieving a fitting accuracy comparable to those obtained from simulated data with statistical noise. Crucially, this capability provides access to
phonon information across the entire Brillouin Zone, a critical component of
lattice dynamics unavailable via standard laboratory techniques like first-order Raman spectroscopy. This low-barrier approach makes synchrotron-level
lattice dynamics characterization accessible to virtually any research laboratory, enabling new avenues for the study of intrinsic strain and anisotropic
lattice dynamics in emerging material systems.
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All authors Paulo H. V. da Silva, Tarsis M. Germano, Rafaela F. S. Penacchio, Sergio L. Morelhao
Materials Science
Charge-State Dependence of Electronic Excitations in keV Ions Transmitted Through Solids Probed by Ion-Photon Coincidence Measurements
Kevin Vomschee, Radek Holeňák, Svenja Lohmann et al. (+2 more)
Investigating the electronic excitations caused by light keV ions in matter contributes to a better understanding of materials modification such as space weathering or
plasma-wall interactions in fusion reactors as well as improved materials analysis methods such as low or medium energy ion scattering. This study investigates the dependence of specific excitations in keV He projectiles, the most common projectile employed in these analytical methods, on the kinetic energy of the ion. We report on
photon emission at energies >10eV emitted by projectiles excited upon transmission through different sample systems. We separate exit charge states and report on measurements of ion-
photon pairs in coincidence, i.e. we can link a
photon to the specific ion emitting it. From these measurements we extracted charge state resolved
photon yields and obtained a deep insight into the electronic excitation occurring. Our results show that the electronic excitation of the helium projectile is largely material independent and rising strongly with the kinetic energy of the projectile. The
photon yields are in good agreement with a common excitation model initially developed for beam foil spectroscopy. We hence extend the validity of this model to higher
photon energies and different sample materials. We further provide a detailed analysis of the employed coincidence approach and necessary corrections to the raw data, as the methodology has a broad applicability in fundamental research and materials analysis.
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All authors Kevin Vomschee, Radek Holeňák, Svenja Lohmann, Eleni Ntemou, Daniel Primetzhofer
Materials Science
Layer-Controlled Intermolecular Coupling and Many-Body Effects in C$_{60}$ Films
Hai-Lan Luo, Weitang Li, Luca Moreschini et al. (+4 more)
Crystalline C$_{60}$ is a molecular solid whose electronic properties emerge from the interplay of intermolecular hopping, electron correlations, and electron-vibration coupling. Unlike moir$\rm\acute{e}$ van der Waals
heterostructures, where interaction strength is commonly tuned by twist angle, molecular materials offer a complementary route in which layer number, molecular orientation, and substrate registry provide experimentally accessible control parameters. Here we present a systematic thickness-dependent angle-resolved photoemission study of C$_{60}$ films, spanning the monolayer to the bulk limit. The HOMO-derived band exhibits a non-monotonic
evolution: the intermediate-thickness film shows larger bandwidth, reduced effective mass, and pronounced gap-like and sub-band features. The experimental trends, together with Holstein-model simulations, point to strengthened effective intermolecular electronic coupling and enhanced electron-
phonon-induced spectral renormalization in the intermediate-thickness regime. These results identify a dimensional crossover in C$_{60}$ films and establish layer number as an effective knob for engineering electronic structure and many-body interactions in molecular thin films.
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All authors Hai-Lan Luo, Weitang Li, Luca Moreschini, Jonathan Denlinger, Zhigang Shuai, Claudia Ojeda-Aristizabal, Alessandra Lanzara
Materials Science
Switchable chiral antiferromagnetism through nonlinear magnetic susceptibility
Hua Chen and Philipp Gegenwart
Antiferromagnets (AFM) have attracted considerable
attention in recent years because a number of nontrivial, technologically relevant properties associated with time-reversal
symmetry (TRS) breaking are discovered in many materials. However, time-reversal (TR) partners of AFM states are generally challenging to be selected deterministically except in a few cases with nonzero net magnetization. Recently, it has been shown that the TR partners of the kagome
spin ice ground state in HoAgGe with strictly zero net magnetization can be selected through a nonlinear
magnetic susceptibility $\chi^{(1)}$. In this work, we generalize this scenario to a broad class of chiral AFM with zero net magnetization but field-switchable ground states through $\chi^{(1)}$. After a general discussion of $\chi^{(1)}$ and its
symmetry constraints, we first present a first-principles formalism for calculating it including both mean-field and self-consistent corrections, and then apply the approach to the noncollinear AFM family Mn$_3X$N ($X=$ Ni, Ag, Ga, Zn, Sn) in the $\Gamma_{5g}$ phase. An intuitive picture of the origin of $\chi^{(1)}$ in similar noncollinear AFM is illustrated using 3-sublattice toy model. The model also predicts a nontrivial temperature dependence of $\chi^{(1)}$ due to competitions between the longitudinal and transverse single-
spin susceptibilities. Our work shows that nonlinear susceptibility can serve as a general protocol for accessing and switching TR partners in fully compensated AFM.
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Materials Science
Modifying van der Waals Materials via Cavity Vacuum Fluctuations
Mohammad Hassan, Cankut Tasci, Leon Orlov-Sullivan et al. (+2 more)
In the field of cavity
quantum materials,
vacuum fluctuations of optical cavities are used for modifying ground-state properties of
quantum materials without external driving. Here, one example is the van der Waals (vdW)/dispersion interaction in layered 2D vdW materials, where non-additive long-range correlations can dominate the interlayer binding. While cavity-induced changes of such interactions have been predicted and described using ab initio methods for molecular systems, no efficient description exists yet for extended materials. In this Letter, we close this gap by introducing a periodic formulation of the
photon many-body dispersion (pMBD) functional within
quantum electrodynamical density-functional theory (QEDFT). Applying this method with efficient $\textbf{q}$-point sampling to bilayer hBN and
graphene, we predict cavity-modified stacking, increased
equilibrium interlayer distances, and softened layer breathing modes with increasing light-matter coupling strength. Our results establish cavity
vacuum fluctuations as a tuning knob for the structural properties of vdW materials.
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All authors Mohammad Hassan, Cankut Tasci, Leon Orlov-Sullivan, Leonardo A. Cunha, Johannes Flick
Materials Science
Automated Dislocation Detection in Electron Channelling Contrast Imaging: A Comparative Study of Rule-Based, Neural Network, and Deep Learning Approaches
A. Holmes, C. Trager-Cowan, J. Bruckbauer et al. (+1 more)
Quantifying threading dislocations in
semiconductor materials via electron channelling contrast imaging (ECCI) is heavily bottlenecked by slow manual analysis. This work
benchmarks three automated detection pipelines on ECCI micrographs of gallium nitride (GaN) against a statistical ground truth. A classical rule-based computer
vision approach proved unreliable due to extensive per-image tuning requirements, while a convolutional neural network (CNN)-based multi-stage classification and locator method achieved 87% accuracy but required significant time for a test image and was less efficient in high-density regions. By contrast, a unified single-stage you only look once (YOLOv8) architecture achieved a counting accuracy of 98.6%, alongside 98.7% precision and 98.7% recall across 7451 dislocations over multiple images, with rapid inference times. Successful deployment of YOLOv8 required addressing two domain-specific machine learning challenges. First, to mitigate the model's scale sensitivity, an adaptive gaussian tile-sizing
algorithm was developed to optimise the field of view per image. Second, the deployed confidence threshold (0.025) differed substantially from the suggested inference default value for YOLOv8 (0.25), raising counting accuracy from 90.8% to 99.3% on a subsection of the
benchmark image. In this case, low confidence scores represented physical signal strength rather than classification ambiguity. This unified, scale-adaptive approach demonstrates practical viability for high-throughput, quantitative
semiconductor defect characterisation.
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All authors A. Holmes, C. Trager-Cowan, J. Bruckbauer, B. Hourahine
Materials Science
Wyckoff-Resolved Oxidation-State Atlas and Anion-Conditioned Priors for Materials Discovery
Boris Kiefer
We introduce a Wyckoff-resolved oxidation-state atlas and assignment utility for probabilityranked, charge-neutral assignment from compositions or Wyckoff grammars. The atlas is constructed from a May 2026 snapshot of 154,879 Materials Project-derived structures by staged exact-neutral enumeration over common and known nonzero oxidation states. The learned prior assigns 106,053 materials in composition mode and 114,403 in Wyckoff mode, compared with a broad MP all-integer possible species count of 108,642. A matched MP baseline requiring at least one charge-neutral assignment with exactly one nonzero integer oxidation state per element contains 89,374 materials; relative to this baseline, composition and Wyckoff modes increase coverage by 18.7% and 28.0%. Of the 14,665 materials recovered only in Wyckoff mode, 99.98% exhibit distinct formal oxidation states for the same element on different site
tokens. The CSV/Python workflow provides a reproducible prior for structure decoration, generative
crystal models, and symbolic Wyckoff-grammar workflows.
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Materials Science · Cross-listed from cs.LG
Euclidean Fourier Neural Operators
Nathanael Bosch, Niklas Frederik Schmitz and Michael F. Herbst
Fourier neural operators (FNOs) provide an efficient framework for learning mappings between function spaces as they are, by construction, independent of the grid resolution at which they are trained and evaluated. However, FNOs are not independent of the periodic domain they are applied to: their discrete spectral weights are indexed by integer
Fourier mode numbers, which correspond to physical wavevectors. When applied to a different domain, the same trained weights act at different wavevectors, and the FNO silently represents a different operator. This makes FNOs unsuitable for tasks where transfer across domains is crucial. We propose Euclidean
Fourier neural operators~(EFNOs) as a domain-independent alternative to FNOs. By parameterizing the spectral kernel as a continuous function of the physical wavevector, the EFNO can learn operators that act consistently across periodic domains of varying shape and size. We evaluate the EFNO on a simple heat equation and on a practically relevant materials science task of learning exchange-correlation potentials across different
crystal structures, and demonstrate that the EFNO is able to generalize to unseen grid sizes and domains.
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Materials Science
Topological Signatures of Hardness and Structural Order in Network-Forming Materials
Yair Augusto Gutiérrez Fosado, Ayobami Daramola, Davide Marenduzzo et al. (+1 more)
Understanding how the
topology of network forming materials influences their physical properties remains a longstanding challenge. Here, we investigate the
topology of experimentally compatible atomistic models of amorphous silica together with the crystalline polymorphs cristobalite and quartz. By comparing multiple atomistic models of amorphous silica that equally reproduce
neutron-scattering data, we show that different microscopic descriptions can imply different topological interpretations of glass stability. To characterize the network beyond conventional
geometric descriptors, we introduce the linking valence, which quantifies the average number of topological links per network loop. This topological descriptor separates silica into two distinct classes: the mechanically harder quartz exhibit values more than an order of magnitude larger than those of amorphous silica and cristobalite, despite their common tetrahedral building blocks. Spectral analysis of the loop-linking networks provides a complementary distinction, separating amorphous from crystalline phases and revealing differences in the long-range organization of topological constraints. These results establish topological linking as a new framework for connecting the structure and physical properties of network-forming materials.
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All authors Yair Augusto Gutiérrez Fosado, Ayobami Daramola, Davide Marenduzzo, Ciprian G. Pruteanu
Materials Science
Work Function and High-Coverage Adsorption Energy as Hydrogen-Evolution Descriptors on Ag-Au-Pd-Pt Alloys
Zacharias Liasi, Ridha Zerdoumi, Felix Thelen et al. (+8 more)
Hydrogen-
evolution activity is commonly rationalized through hydrogen adsorption energies and the Sabatier principle, yet this descriptor picture becomes ambiguous on multimetallic surfaces, where each composition exposes a distribution of local adsorption environments. Here we investigate whether the bare-surface work function, previously shown to add predictive information for monometallic surfaces, remains an activity descriptor for compositionally complex surfaces. We test this on three combinatorial Ag-Au-Pd-Pt thin-film materials libraries screened for acidic hydrogen
evolution by scanning electrochemical
cell microscopy. Graph neural networks provide adsorption-energy distributions and work functions for each measured composition. A work-function-only model explained most of the activity variation (mean $R^2_\mathrm{log}$ = 0.903), as did a coverage-corrected adsorption model (mean $R^2_\mathrm{log}$ = 0.955), outperforming dilute adsorption (mean $R^2_\mathrm{log}$ = 0.758). Combining work function and coverage-corrected adsorption yielded the highest fit quality (mean $R^2_\mathrm{log}$ = 0.969), but only a small gain over coverage-corrected adsorption alone. For these four metals the coverage-corrected adsorption energy and work function follow a similar trend, producing similar activity rankings, hence including both adds little beyond either one individually, although both are strong predictors.
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All authors Zacharias Liasi, Ridha Zerdoumi, Felix Thelen, Geovane Arruda de Oliveira, Rico Zehl, Natalia Pukhareva, Leonardo H. Morais, Henrik H. Kristoffersen, Alfred Ludwig, Wolfgang Schuhmann, Jan Rossmeisl
Materials Science · Cross-listed from physics.ins-det
Full-field fluorescence computed tomography (F3CT) using a calibrated virtual cone-beam pinhole geometry
Thomas Zillhardt, Yunhui Chen, Alexander Rack et al. (+4 more)
We present F3CT, a synchrotron-based hyperspectral full-field fluorescence computed
tomography technique that avoids raster scanning by combining a pinhole aperture with an energy-resolving 2D detector. A virtual cone-beam model and two-stage calibration-reconstruction workflow enable 3D elemental mapping under full-field illumination. The method is demonstrated on biological and geological specimens, resolving silver-stain distributions in zebrafish tissue and high-energy fluorescence signatures in rock cores. Phase-contrast tomograms acquired sequentially under the same experimental geometry provide co-registered structural context. F3CT provides a high-throughput route to 3D XRF imaging and establishes a foundation for correlated structural and chemical
tomography, with potential for future in-situ and operando implementations.
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All authors Thomas Zillhardt, Yunhui Chen, Alexander Rack, Matthew Veale, Matt Wilson, Philip J. Withers, Nicola Viganò
Materials Science
Phenomenological Growth Regimes in Liquid-Precursor CVD of MoS$_2$ on Functional Substrates
Osamah Kharsah, Kilian Mouchel, Yossarian Liebsch et al. (+8 more)
The integration of two-dimensional transition-metal dichalcogenides (TMDCs) onto functional substrates remains constrained by
stochastic vapor-phase growth dynamics. Here, we show that
liquid-phase precursor chemical vapor deposition (CVD) of MoS$_2$ introduces growth conditions that are consistent with a substrate-influenced reaction-
diffusion process. By utilizing pre-growth
spin-coated MoO$_3$ intermediates across a diverse crystalline library (sapphire, SrTiO$_3$, rutile TiO$_2$, MgO, and 6H-SiC), we find that substrate-dependent variations in precursor wetting, surface chemistry, and inferred mass-transport constraints correlate with distinct growth morphologies. These substrate-dependent growth regimes are interpreted in terms of reduced effective lateral growth length on SrTiO$_3$, possible precursor anchoring on TiO$_2$, likely chemical surface restructuring on MgO, and possible step-edge growth on SiC. Raman and photoluminescence spectroscopy reveal substrate-dependent variations in vibrational and optical response that correlate with differences in strain, charge environment, and dielectric screening. Ultimately, this work highlights a substrate-dependent reaction-
diffusion framework as a potentially useful route for tuning the structural and optical properties of large-area 2D materials.
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All authors Osamah Kharsah, Kilian Mouchel, Yossarian Liebsch, Cathy Sulaiman, Joel Verlande, Anke Hierzenberger, Abdallah Alghazali, Clara Grygiel, Stéphane Guillous, Henning Lebius, Marika Schleberger
Materials Science
Nanolamellar Hybrid High-Entropy Alloys with Superior Micromechanical Properties
Shivam Dangwal, Yoji Mine, Shohei Ueki et al. (+5 more)
Metallic materials with nanolamellar structures, such as pearlitic steels, exhibit high strength with appropriate ductility. Considering the potential ability of such nanolamellar structures to break the traditional strength-ductility trade-off in metallic
alloys, this study aims at developing a unique nanolamellar structure with superior micromechanical properties by combining two different high-
entropy alloys (HEAs). Al0.1CoCrFeNi with the face-centered cubic (FCC) structure is combined with TiZrHfNbTa with the body-centered cubic (BCC) structure using high-pressure torsion (HPT) of half discs of each
alloy. That way, a layered hybrid structure was formed, with layer thickness down to about 61 nm. The BCC/FCC nanolamellar hybrid structure exhibits an exceptional combination of properties with an ultimate tensile strength of 2.4 GPa, a maximum bending strength of 4.0 GPa, and a hardness of 740 Hv, while retaining some ductility/plasticity under both tensile and bending loads. Detailed analyses by synchrotron diffraction, electron microscopy and atom probe
tomography suggests that these high strength and hardness, which are superior to those of nanostructured HEAs, result from: (i) extreme grain boundary strengthening from nanograins with a mean size of 22 nm, (ii) presence of defects such as dislocations in FCC and BCC, stacking faults in FCC and twins in FCC, and (iii) interphase hardening from BCC/FCC nanolamellar boundaries with about 30% contribution to the total hardness. This work demonstrates that combining two HEAs using HPT into a defect-rich hybrid nanolamellar composite forms a promising synergy of ultrahigh strength and reasonable ductility/plasticity.
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All authors Shivam Dangwal, Yoji Mine, Shohei Ueki, Xavier Sauvage, Fabien Cuvilly, Liliana Romero Resendiz, Muhammad Naeem, Kaveh Edalati
Materials Science
QUBO-Compatible Active Learning for Inverse Design of High-Entropy Alloys
Giorgio Silvi, Kirsten Bark, Rolando Reiner et al. (+5 more)
Machine-learned forward models can rapidly predict
alloy properties, but their use for inverse design remains challenging when the search should also retain compatibility with quadratic unconstrained binary optimization (QUBO). Here, we develop a QUBO-compatible active-learning framework for inverse design of high-
entropy alloys using a pretrained graph-neural-network predictor as a fixed property oracle. A property-guided binary variational autoencoder provides a binary latent representation, while an ensemble of quadratic factorization machines guides candidate selection. We systematically
benchmark the framework through controlled latent-space ablations and comparison with direct composition-space optimization. The results show that candidate generation is a major determinant of search performance: local perturbations around previously high-performing latent codes provide the largest workflow-specific improvement, while surrogate-based selection further prioritizes candidates within the enriched search pool. The resulting QUBO-compatible workflow remains competitive with strong classical optimization strategies, although a composition-space genetic
algorithm achieves the highest mean score. Finally, the learned quadratic surrogate can be exported directly as a QUBO. These results show that effective data acquisition can be separated from the final QUBO optimization endpoint, providing a benchmarked route for QUBO-compatible data-driven materials inverse design.
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All authors Giorgio Silvi, Kirsten Bark, Rolando Reiner, Nicolas Vogt, Thomas Plehn, Daniel Barragan-Yani, Marc Landmann, David Melching
Materials Science
Interplay between crystal structure and magnetism in CeCrB$_4$
Mirosław Werwiński, Andrzej Szajek and Andrzej Kowalczyk
CeCrB$_4$ belongs to the family of MTB$_4$ ternary metal borides, some of whose
magnetic phases have recently been identified as
quantum spin dimers. Employing density functional theory within the GGA+$U$ framework, this work investigates the key ground-state properties of this system, including its ferromagnetic ground state, the mixed-valence nature of cerium, and the charge transfer from the cationic cerium–chromium layers to the anionic boron layers. In particular, we focus on elucidating the bonding mechanism within the structurally embedded Cr-Cr dimers. Specifically, we evaluate a previously proposed interpretation that the localized Cr $3d_{z^2}$ states are molecular-like bonding and antibonding states. The calculated dependence of the $3d_{z^2}$ electronic structure on the intra-dimer distance correlates with the level-splitting characteristics known for classical homonuclear diatomic molecules.
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Materials Science · Cross-listed from cond-mat.mes-hall
Quantum Geometric Origin of Nonlinear Current Induced Orbital Magnetization
Xue-Jin Zhang, Yue-Xin Huang, Wei Du et al. (+5 more)
Electric generation of magnetization is a focus of condensed matter research, and has recently been advanced into the nonlinear regime. However, due to the nonlocal nature of orbital magnetism, how to properly formulate nonlinear current-induced orbital magnetization remains a fundamental challenge. Here, we develop the proper theory for this effect. This is based on the microscopic derivation of field-corrected orbital
magnetic moment of a Bloch electron, a critical missing piece in the present theory. We show that the
quantum geometric origin of this phenomenon lies in both the anomalous orbital polarizability and the Berry-connection polarizability, which often provide competing contributions. Combining our theory with first-principles calculations, we predict significant, experimentally accessible nonlinear orbital magnetization generated in strained bilayer
graphene, monolayer 1T' $\mathrm{MoS_2}$ and $\mathrm{MoTe_2}$. Remarkably, nonlinear orbital magnetization can dominate over its
spin counterpart in materials with topological band features, irrespective of the
spin-orbit coupling strength.
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All authors Xue-Jin Zhang, Yue-Xin Huang, Wei Du, Xiaolong Feng, Shen Lai, Cong Xiao, Qian Niu, Shengyuan A. Yang
Materials Science
Light-induced atomic motion in ionic crystals
Jacob C. Warming, Simon P. S. Jessen, Emma A. Husted et al. (+5 more)
Atomic motion in solids is conventionally driven by elastic collisions between ionizing particles and atoms, which transfer momentum and induce
lattice displacements. In this work, we demonstrate a different mechanism for atomic displacement based on optical excitation of scintillating ionic
crystals. Ionic
crystals are unique systems because of the closed-shell electronic configuration of their constituent ions. In these materials, excitation above the band gap generates a hole that strongly distorts the
lattice, resulting in the formation of a self-trapped hole (STH). The STH is Coulomb-attracted to the electron, thereby forming a self-trapped
exciton (STE). Here, we demonstrate that in BaF2 - one of the fastest scintillators - the STE structure promotes the formation of long-lived electron and hole traps that persist in the
lattice at room temperature. Such trapped electron-hole pairs occupy vacancy-interstitial fluorine pair positions, and can be created indiscernibly using optical or ionizing radiation excitation, as long as the STH is formed. Further, we demonstrate that it is possible to control the defect
evolution with light. Selective optical stimulation of the trapped electrons or holes enables the regeneration of the STE at later times. This light-controlled defect engineering allows us to increase the yield of the STE signal appearing as optically stimulated luminescence (OSL) and to image the spatial distribution of the initial energy deposition, holding strong potential for ionizing-radiation detection. These findings provide a common framework underlying scintillation and OSL in ionic
crystals of the fluorite structure, allowing for optical manipulation of atomic vacancies-interstitial pairs in similar systems.
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All authors Jacob C. Warming, Simon P. S. Jessen, Emma A. Husted, Jan Thøgersen, Stefan Gundacker, Brian Julsgaard, Peter Balling, Rosana M. Turtos
Materials Science
Charge transfer and competing symmetry breaking drive orbital reconstruction and emergent ferromagnetism in insulating oxide superlattices
Nandana Bhattacharya, Ranjan Kumar Patel, Siddharth Kumar et al. (+13 more)
Electron correlation, hopping, and ligand-to-metal charge transfer collectively lead to diverse electronic and
magnetic phenomena in 3$d$ transition-metal oxides, where directional d orbitals make hopping highly sensitive to
symmetry-dependent orbital overlap.
Heterostructure engineering with atomically flat interfaces adds
symmetry-breaking charge transfer as a further route to emergent behavior, yet whether interfacial mismatch between constituent oxides of a superlattice shapes ground states independent of epitaxial strain remains unresolved. Here we examine superlattices combining NdNiO$_3$ with Mott-insulating NdMnO$_3$. Varying layer thickness and combining transport with X-ray spectroscopy, we show that electron transfer from NdMnO$_3$ to NdNiO$_3$ drives a room-temperature insulating state with a distinct electronic structure, accompanied by a reversal in orbital
symmetry beyond simple strain considerations, underscoring the interface's central role. These reconstructions stabilize an emergent ferromagnetic insulating state arising from interfacial Ni$^{2+}$-O-Mn$^{4+}$ superexchange. Our results establish a pathway to interface-engineered ferromagnetic insulating phases via competing interactions, with potential for
spin-insulatronic applications.
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All authors Nandana Bhattacharya, Ranjan Kumar Patel, Siddharth Kumar, Sourav Chowdhury, Manav Beniwal, Suresh Chandra Joshi, Prithwijit Mandal, Jayjit Kumar Dey, Weibin Li, Manuel Valvidares, Zhan Zhang, Hua Zhou, Andrei Gloskovskii, Christoph Schlueter, Christoph Klewe, Srimanta Middey
Materials Science
Band-like Carriers in a Soft, Anharmonic Lattice: Lead-Halide Perovskites
Young Mi Lee, Inhee Maeng, Jinwoo Park et al. (+2 more)
Lead-halide perovskites APbX3 present a striking dichotomy: they exhibit band-like electronic transport despite their exceptionally soft and anharmonic
lattices. Optically and electrically, they resemble conventional direct-gap
semiconductors, exhibiting light carrier masses and steep absorption onsets, whereas their
lattices display
liquid-like dynamics, including overdamped octahedral motions, quasielastic Raman central peaks, and exceptionally low thermal conductivities. Solution-processed films nevertheless sustain micrometre-scale carrier
diffusion at defect densities that would severely suppress transport in conventional
semiconductors. Here, we argue that these apparently disparate properties emerge from a common microscopic framework: a soft, strongly anharmonic, and polar [PbX3]- framework, strongly influenced by the Pb 6s2 lone pair, which simultaneously shapes the antibonding orbital character of the band edges, the magnitude and multiple timescales of the dielectric response, and the slow relaxational dynamics that dress every charge carrier. We therefore invert the conventional order and develop the
lattice before the electronic structure, because the nominally cubic phase is better viewed as a thermally fluctuating ensemble of locally
symmetry-broken configurations rather than a single geometry. Within this framework, we discuss
excitons, Frohlich large polarons in the intermediate-coupling regime, carrier transport, defect tolerance, dimensional reduction in two-dimensional and nanocrystalline derivatives, and
symmetry-breaking phenomena. We critically assess three contested issues - defect tolerance, ferroelectricity, and the interpretation of the T-3/2 mobility law - and identify seven open questions together with the key measurements needed to resolve them
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All authors Young Mi Lee, Inhee Maeng, Jinwoo Park, Seung-Jae Oh, Min-Cherl Jung
Materials Science
uMOF: A Universal Database, Benchmark, and Machine Learning Interatomic Potentials for Metal-Organic Frameworks
Théo Jaffrelot Inizan, Prathami Divakar Kamath, Alin Marin Elena et al. (+1 more)
Foundation machine learning interatomic potentials (MLIPs) deliver near-ab-initio accuracy at a fraction of the computational cost, yet their promise for Metal-organic Frameworks (MOFs) remains largely unrealized as large unit
cells make first-principles training data expensive to generate, fine-tuned models are scarce, and experimentally grounded
benchmarks are scarcer still. We introduce uMOF, a three-part contribution addressing this gap. First, we release the largest and most accurate density functional theory
dataset for MOFs to date, computed at the r$^2$SCAN-D4 level of theory across 85524 configurations spanning 19950 unique frameworks and 79 elements, covering empty and gas-loaded structures, geometry optimizations, equations of state, and finite-temperature molecular dynamics. Second, we release a literature-mined
benchmark of 3986 verified property values (3146 experimental) extracted from 626 papers by a seven-stage, checkpointed multi-pass large
language model pipeline, linked to more than 650 crystallographic information files. Third, we release two universal MLIPs for MOFs, uMOF-MH and uMOF-POLAR, fine-tuned from two architecturally distinct MACE foundation models on the uMOF
dataset. On near-
equilibrium, “Tier-1” properties (bulk modulus,
phonon-derived heat capacity) the uMOF models perform comparably to existing foundation and fine-tuned baselines. On harder, dynamics-sensitive properties like gas adsorption enthalpies via Widom insertion and adsorption isotherms, the uMOF models outperform every baseline we test, including MOF-specialized gas-capture models trained on
datasets up to three orders of magnitude larger, cutting error by more than 80% to within experimental uncertainty. We trace this advantage to the physical diversity of the training data and to level of theory where a small (1.7%) fraction of MD simulations is decisive for MLIP stability.
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All authors Théo Jaffrelot Inizan, Prathami Divakar Kamath, Alin Marin Elena, Kristin A. Persson
Materials Science · Cross-listed from cond-mat.soft
How a polymer filling enhances the rate and selectivity of colloid permeation across mesopores
Mikhail Y. Laktionov, Frans A. M. Leermakers, Ralf P. Richter et al. (+2 more)
Polymer-functionalised mesopores are an emerging technology for colloid separation, sensing and delivery. Their potential is strikingly illustrated in living
cells, where nuclear pore complexes (NPCs) control biocolloid transport between the
nucleus and the cytosol. Even colloids much smaller than the biopolymer-filled NPC channel are effectively blocked, but some larger colloids with distinct surface features rapidly permeate. Simplistically, one may expect any
polymer filling to obstruct and slow down colloid transport. We demonstrate how a
polymer filling that attracts colloids and extends beyond the mesopore, thus maximizing colloid capture, can instead increase permeation compared to a bare pore. We also define how
polymer-filled mesopores can effectively gate colloids according to their size and surface features. Our findings provide a basic physical explanation for the exquisite permselectivity of NPCs, and a rational design strategy for novel mesopore-based separation, sensing, catalysis and drug delivery devices with enhanced performance features.
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All authors Mikhail Y. Laktionov, Frans A. M. Leermakers, Ralf P. Richter, Leonid I. Klushin, Oleg V. Borisov
Materials Science · Cross-listed from physics.optics
Compact Variational Neural Networks for Spectral Inference from a Single Nonlinear 2D Perovskite Photodetector
Karl Jonas Riisnaes, Ned Thaddeus Taylor, Hoi Tung Lam et al. (+4 more)
Spectroscopy conventionally separates optical frequencies before detection, imposing persistent constraints on footprint, complexity and scalability. Here we establish an alternative paradigm in which the nonlinear optoelectronic dynamics of a single two-dimensional perovskite photodetector physically encode the incident optical field and machine learning performs the inverse spectral reconstruction. Using a planar fluorinated phenethylammonium lead iodide (F-PEAI) photodetector, we exploit wavelength- and irradiance-dependent current-voltage signatures arising from the coupled effects of photocarrier generation, trapping, interfacial transport and field-dependent carrier dynamics. A compact variational encoder-decoder preserves the functional and history-dependent structure of these responses by independently projecting forward and reverse voltage sweeps onto a truncated Legendre-
polynomial basis before mapping them through a probabilistic latent representation to continuous spectral parameters. Trained on fewer than 400 experimental voltage sweeps, the model generalises to excitation wavelengths excluded from training, reconstructing wavelength with $R^2=0.958$ and a mean absolute error of 8.1 nm, while recovering log-normalised irradiance with $R^2=0.987$. Voltage-resolved analysis further reveals that wavelength and irradiance are encoded differently across the nonlinear device response, with distinct bias regions carrying complementary optical information. These results establish nonlinear material and interface dynamics as a computational resource for spectroscopy and point towards hardware-
algorithm co-design in which materials, interfaces and inference architectures are engineered jointly to maximise information content, enabling compact spectroscopic systems without dispersive optics or detector arrays.
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All authors Karl Jonas Riisnaes, Ned Thaddeus Taylor, Hoi Tung Lam, Rosanna Mastria, Francesco Saverio Difeo, Monica Felicia Craciun, Saverio Russo
Materials Science · Cross-listed from cond-mat.soft
Steady shear rheology of a granular crystal containing a single dislocation
Fumiaki Nakai
Monodisperse granular particles can form
crystals whose yielding behavior is strongly affected by dislocations and differs markedly from that of conventional amorphous granular materials. Yet the rate dependence of their post-yield steady rheology remains unclear. We use the discrete element method to study steady shear in a granular
crystal containing a single dislocation. We find that the steady shear-to-normal stress ratio $\mu_b$ is organized by the scaled dislocation velocity $v_d/v_s$, rather than by the conventional inertial number $I$. Here, $v_d$ is related to the imposed shear rate through Orowan kinematics, and $v_s$ is a characteristic Hertzian elastic-wave speed. At low $v_d/v_s$, the stress ratio approaches a small plateau associated with the elastic
lattice barrier and interparticle friction. At intermediate values of $v_d/v_s$, contact damping strongly affects the approximately linear increase of the stress ratio above the plateau. As $v_d/v_s$ approaches unity, the stress develops a stronger nonlinear velocity dependence. At still higher velocities, the coordination deficit rises sharply, marking the breakdown of crystalline order and the end of the single-dislocation description. These results identify the scaled dislocation velocity as the relevant rate variable for the steady rheology of dislocation-mediated granular flow and clarify the distinct roles of interparticle friction and contact damping in the low- and intermediate-velocity regimes, respectively.
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Materials Science
Ionization Energies, Electron Affinities, Bandgaps, Exciton Binding Energies, and Polarization Energies of Orientation-Controlled Picene, [6]-Phenacene, and [7]-Phenacene Thin Films
Rintaro Makino, Mihiro Kubo, Keiichirou Yonezawa et al. (+2 more)
Phenacenes, in which benzene rings are fused in a zigzag manner, are chemically robust $\pi$-conjugated hydrocarbons of interest for organic electronic applications and superconductivity. However, quantitative electronic parameters of phenacene thin films remain limited compared with those of acenes. Here, we determine the ionization energies (IEs), electron affinities (EAs), band gaps,
exciton binding energies, and polarization energies of orientation-controlled thin films of picene, [6]-phenacene, and [7]-phenacene using ultraviolet photoelectron spectroscopy and low-energy inverse photoelectron spectroscopy. The energy parameters depend only weakly on molecular size. In contrast, both IE and EA exhibit large orientation-dependent shifts of approximately 1 eV: lying films show IEs of 6.41-6.43 eV and EAs of 2.16-2.42 eV, whereas standing films show IEs of 5.44-5.67 eV and EAs of 1.36-1.53 eV. Nevertheless, the band gaps of approximately 4 eV and
exciton binding energies of approximately 1 eV remain nearly independent of molecular size and orientation. Analysis of polarization energies shows that the induction term is nearly orientation independent, whereas the electrostatic term strongly depends on orientation and originates primarily from molecular quadrupole moments. These results identify molecular orientation as a key factor governing frontier energy levels in phenacene thin films.
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All authors Rintaro Makino, Mihiro Kubo, Keiichirou Yonezawa, Hiroyuki Yoshida, Satoshi Kera
Materials Science · Cross-listed from physics.chem-ph
Mode-Specific Dynamics of $\text{CO}_2$ Hydrogenation on Copper: The Hidden Role of Molecular Rotation
Junfan Xia, Zhikai Jiang, Yaolong Zhang et al. (+3 more)
Catalytic hydrogenation of $\text{CO}_2$ to formate on copper is a key elementary step for $\text{CO}_2$ utilization. Previous experimental and theoretical studies suggested an Eley-Rideal mechanism for this reaction, promoted by bending vibrational excitation, yet direct state resolved evidence remains lacking. Here, we present first-principles dynamical predictions for $\text{CO}_2$ hydrogenation on Cu(111) based on an accurate full-dimensional neural network potential energy surface. Our calculations near-quantitatively reproduce the measured reaction probabilities, including their nozzle-temperature and incidence-energy dependence. Our state-resolved results indicate that while vibrational excitation of the bending mode enhances reactivity, it alone cannot account for the observed reactivity increase with nozzle temperature. Instead, rotational excitation plays a dominant role, mainly attributable to the significant change in anisotropy of the molecular polar orientation as $\text{CO}_2$ accesses the transition state. This mode-specific insight reinforces the hidden role of rotation in surface reactivity, opening new avenues for state-selective control of $\text{CO}_2$ hydrogenation on heterogenous catalysts.
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All authors Junfan Xia, Zhikai Jiang, Yaolong Zhang, Bo Peng, Hua Guo, Bin Jiang
Materials Science
Compositionally Complex Ceramics
Jian Luo
The development of high-
entropy ceramics (HECs) over the past decade has extended the high-
entropy concept to a diverse range of oxides, borides, silicides, carbides, nitrides, fluorides, silicates, and other ceramic solid solutions, encompassing increasingly diverse
crystal structures and bonding characteristics and exhibiting a broad spectrum of promising mechanical, thermal, and functional properties. Initial studies predominantly focused on five-component equimolar compositions, often assuming the formation of random solid solutions. More recently, 10-21 component ultrahigh-
entropy ceramics have been developed as a subset of HECs, some of which exhibit intriguing abrupt phase transitions. In 2020, we proposed extending the exploration of HECs to the broader class of "compositionally complex ceramics" (CCCs), in which non-equimolar compositions and long- and short-range order reduce configurational
entropy while providing additional opportunities to tailor and enhance materials properties, thereby outperforming their higher-
entropy counterparts. Dual-phase CCCs have also been reported, with thermodynamic
equilibria governing cation partitioning between the two phases and offering further opportunities to control and enhance properties through microstructural engineering. Subsequent studies have revealed grain-boundary phase-like transitions in CCCs that can control microstructural
evolution and materials properties. Overall, CCCs offer a versatile platform for tailoring materials properties through diverse
crystal structures and bonding characteristics, compositional complexity, non-equimolar designs, long- and short-range order, defects, and microstructural and interfacial engineering.
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