Materials Science
Vitriflow: calibrated amorphous structure ensembles from melt-quench simulation
Jonathon Cottom, Robin Delhomme and Emilia Olsson
Many structure-property relations in amorphous materials are encoded not only in the mean structure, but in the prevalence, correlations and spatial organisation of minority environments across length scales. Yet atomistic models are commonly validated against bulk averages and a nominal number of structures, without establishing whether the finite population resolves the motifs invoked to explain material behaviour. We present an auditable framework, implemented in the Vitriflow software package, that connects calibrated melt-quench generation to explicit populations and quantity-specific uncertainty. This approach is demonstrated on three distinct
benchmark systems. In a-SiO$_2$, strain is followed from intra-tetrahedral deformation through compressed Si–O–Si bridges to primitive 3-ring
topology, showing that the lower angular tail is an organised medium-range population rather than undifferentiated variation about the network mean. In matched a-Si$_3$N$_4$ refinements, DFT redistributes density and first-neighbour length scale, sharpens the force-field first shell and repairs marginal contacts, while the two DFT descendants retain essentially the same first-neighbour
topology. In a-Sm$_2$O$_3$, the amount and connectivity of partially ordered domains are quantified as they emerge from the disordered parent population, while the mixed coordination characteristic of the amorphous
oxide remains robust. Mean structure, distribution tails, inherited
topology and connected order are therefore distinct materials variables with distinct uncertainties. There is no universal ensemble size: the Vitriflow package records what was generated, which population was analysed and what that finite population establishes, providing a reproducible route from amorphous structure
datasets to quantitatively supported structure-property hypotheses.
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Materials Science
Microscopic origins of inertial magnetization dynamics
Caleb Webb, Ling Gan and Shufeng Zhang
Ultrafast experiments have uncovered inertial magnetization dynamics in ferromagnets, but their microscopic origin remains elusive. Using a non-Markovian
quantum master equation we show that inertial dynamics arise from coherent interactions with optical
phonons in the
lattice. The fast optical frequency explains the nutation observed on picosecond timescales and accounts for variations between experiments through substrate-dependent
phonon damping. By establishing
magnon{
phonon coupling as the microscopic basis of inertial magnetization, our results open new pathways for tailoring ultrafast
spin dynamics and controlling
magnetic states at terahertz frequencies.
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Materials Science
On the limits of the energetic coupling between field dislocation mechanics and phase field crystal
Aymane Graini, Jorge Viñals and Manas V. Upadhyay
This paper investigates the energetic coupling between Field Dislocation Mechanics (FDM) and the Phase Field
Crystal (PFC) model proposed in Phys. Rev. B 102, 064109, 2020. While FDM correctly solves the initial boundary value problem of a continuum body with dislocation fields, PFC captures the underlying crystallographic structure. The coupling, which penalizes the $L^2$ distance between elastic distortion from FDM and configurational distortion from PFC in the $L^2$ sense, had been proposed to reconcile dislocation mechanics with crystallography in a single continuum framework. Variational analysis reveals that the coupling term acts as a divergence-driven forcing in the phase-field
evolution that matches only the compatible (curl-free) parts of the distortion fields. Consequently, its contributions are insensitive to the incompatible (divergence-free) elastic distortion carrying all the information on dislocation
topology. Furthermore, the nature of the configurational distortion causes mechanical boundary conditions to be transmitted diffusively from FDM to PFC rather than elastically. Numerical simulations demonstrate that this coupling cannot prevent the unnatural core spreading in FDM. Finally, it is shown that even in the most general case, an energetic coupling suffers from the same drawbacks, which limits its ability to integrate dislocation mechanics with crystallography.
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Materials Science · Cross-listed from cs.AI
Optimal Resource Utilization for Autonomous Laboratory Orchestrators
Austin McDannald, Julia Tisaranni and Howie Joress
In autonomous laboratories, AI
agents suggest the next batch of experiments to do. However, planning and executing those tasks taking full advantage of the available resources is a completely different question. This can be challenging when dealing with real-world hardware constraints, especially so when there are multiple instruments with different capacities and throughputs. Here we demonstrate a 2-step method to address resource utilization for our autonomous platform for metal-organic framework synthesis. First, we use constraint programming to find optimal schedules. This finds schedules that minimizes the total time while still satisfying the limitations and capacities of the hardware. Secondly, we use a system of status dependencies for each task, which allows for the robust execution of the optimal schedules.
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Materials Science
Observation of Flat Bands in Type-II Weyl Semimetal TaRhTe$_{4}$
Harry Rankin, Tyler J. Slade, Benjamin Schrunk et al. (+7 more)
Flat bands have been theoretically predicted for decades but have only recently been realized in
quantum materials such as magic-angle twisted
bilayer graphene, kagome and Lieb
lattices, and rare-earth metal compounds. To date, only twisted layered materials have enabled tuning of flat-band energies near the electronic chemical potential, thereby influencing transport and thermodynamic properties. Here, we report the presence of flat bands near the chemical potential in bulk TaRhTe$_{4}$, a noncentrosymmetric van-der Waals type-II Weyl semimetal. Flat bands are rarely observed in Weyl semimetals, particularly in nonmagnetic bulk systems, and the observed flat bands were not predicted by density functional theory calculations. TaRhTe$_{4}$ therefore provides a platform in which nontrivial
topology coexists with flat bands near the
Fermi level, as evidenced by our angle-resolved photoemission spectroscopy measurements.
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All authors Harry Rankin, Tyler J. Slade, Benjamin Schrunk, Yevhen Kushnirenko, Andrew Eaton, K. U. R. R. S. Rathnayaka, Maxwell Doyle, Lin-Lin Wang, Paul C. Canfield, Adam Kaminski
Materials Science
Electric-field effects on defect migration energetics in GaN
Farshid Reza, Hamdy Arkoub, Alexander S. Hauck et al. (+2 more)
A predictive understanding of defect transport in GaN under operating electric fields is critical for assessing device reliability in high-power and radiation environments. In this work, a ReaxFF reactive force field for GaN is developed using a density-functional-theory training set that includes structural, thermodynamic, and defect properties. The force field yields various properties such as
lattice parameters, cohesive energies, and defect formation and migration energies in close agreement with prior first-principles and experimental results. Under externally applied electric fields, we find that migration barriers can be strongly modulated, with changes that depend on defect type and field orientation. Notably, the electric fields do not simply linearly bias defect motion in GaN, but can anisotropically modify migration barriers through charge-
lattice coupling, leading to nonlinear transport behavior. The response arises from field-induced partial charge redistribution and local
lattice distortion. These results demonstrate that electric fields can complexly modify the defect migration landscape, providing new insight into defect transport in GaN under high-field conditions.
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All authors Farshid Reza, Hamdy Arkoub, Alexander S. Hauck, Adri C.T. van Duin, Miaomiao Jin
Materials Science
Topological Hall effect due to electron-skyrmion scattering
Arijit Mandal, Hareram Swain, B. R. K. Nanda et al. (+1 more)
Electron scattering from
chiral spin textures such as skyrmions is fundamental to the understanding of transport in more complex systems, including skyrmion
crystals. Most of the previous studies have focused on the weak-coupling regime, where the exchange interaction is small compared with the electron energy. Real materials, however, often lie in the strong-coupling regime, which exhibits qualitatively different behavior. Using the Lippmann-Schwinger equation and Green's function formalism, valid for all coupling strengths, we uncover several new features in the scattering cross section, including Ramsauer-Townsend minima, pronounced intermediate-coupling resonances, and Landau-level resonances for skyrmions with larger winding numbers. These features strongly influence the topological and
spin Hall conductivities, which depend sensitively on the incident electron energy. Our work provides important insights into the
Hall transport in collective
chiral spin textures such as the skyrmion
crystal.
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All authors Arijit Mandal, Hareram Swain, B. R. K. Nanda, S. Satpathy
Materials Science
Diamond Diode for Extreme Venus Environments
Harshad Surdi, Gabriel Munro-Ludders, Mohamadali Malakoutian et al. (+9 more)
A diamond Schottky PIN diode (SPIND) with the highest reported current density to date of ~116 kA/cm2 is demonstrated carrying a total current of ~1.3 A through a 50 micron wide pseudo-vertical diode structure. The diamond SPIND also provides a maximum power handling capacity of 1.85 MW/cm2 and a low specific on-resistance Ron,S of 0.05 mOhm-cm2 at a forward bias of ~16 V. The diamond
SPIN diode also shows excellent rectification characteristics with a current on-off ratio of ~6e12. An analytical model including thermionic emission and space charge limited current is presented together with Silvaco ATLAS TCAD simulations, to accurately reproduce the experimental J-V characteristics using multiple single trap levels and other physical models emulating a real device. Theoretical analysis from the analytical models in conjunction with ATLAS simulations shows that further improvement in the device turn on voltage and Ron,S can be achieved by reducing the defect density and contact resistance in order to approach the ultimate performance in the Mott-Gurney space charge limited current regime
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All authors Harshad Surdi, Gabriel Munro-Ludders, Mohamadali Malakoutian, Srabanti Chowdhury, Savannah Eisner, Mohamed Fadil Isamotu, Mengyang Yuan, Stephen Goodnick, Franz Koeck, James Lyons, Trevor Thornton, Robert Nemanich
Materials Science · Cross-listed from math-ph
Scattering, Trapping and Cloaking-Type Effects of Plane Waves by Point Scatterers in Strain Gradient Elasticity
E. Alevras, Th. Zisis and P. A. Gourgiotis
Wave scattering by localized constraints in microstructured solids is strongly influenced by the interplay of material length scales, dispersion and geometry. This work investigates plane-strain scattering of time-harmonic P and SV waves by clusters of rigid point constraints embedded in an infinite strain gradient elastic medium. A closed-form dynamic Green's tensor is derived for the plane-strain problem. Unlike the classical elastodynamic Green's tensor, the strain gradient Green's tensor remains bounded at the source, enabling point constraints to be introduced directly through superposition of fundamental solutions. The multiple-scattering problem is reduced to a finite-dimensional algebraic system for the pin reaction amplitudes. A frequency-domain procedure is developed to identify resonance-like amplification and trapping. Candidate resonant frequencies are associated with local minima of the Green
matrix determinant, while higher-order
curvature criteria distinguish trapping-dominated resonances from non-localized scattering responses. The results show that the response is governed primarily by the ratio of the microinertial and energetic strain gradient lengths. In the anomalous dispersion regime, sharp resonances produce strong displacement localization, including perimeter-localized trapping modes in dense circular arrays. In the normal dispersion regime, these resonances are strongly attenuated and the pins behave as weak scatterers, producing a cloaking-type response in which the incident field is only weakly perturbed. The influence of Poisson's ratio, incidence angle and compound pin configurations is also examined, demonstrating how intrinsic material lengths and
geometric arrangement can be used to tune scattering, trapping and wave-screening mechanisms in microstructured elastic media.
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Materials Science
Effect of radially heterogeneous band gap collapse on formation of swift heavy ion tracks in Al2O3
Roman Voronkov, Danil Zainutdinov, Nikita Medvedev et al. (+1 more)
We estimate the effects of radial heterogeneity in the collapse of the electronic band gap on the damage in Al2O3 after impact of a swift heavy ion decelerated in the electronic stopping regime. The Monte Carlo code TREKIS describes the initial excitation of the electronic and ionic systems following the ion passage, while the density functional theory based molecular dynamics traces changes in the band structure in the ion track. This combination of methods enables us to compute the profile of energy transferred to the
lattice by the time of relaxation of the electronic excitation, accounting for the induced spatial inhomogeneity of the band structure around the ion trajectory. We demonstrate that impact of a 700 MeV Bi ion induces a transient metal-
semiconductor heterojunction in Al2O3: the metallization (the band gap collapse) occurs within a radius of about 2 nm from the ion trajectory. The band gap shrinks at distances of about 3-5 nm, while it remains almost unaffected at radii larger than 5 nm. Using this data, we estimate the atomic heating depending on the degree of band gap reduction at different radii from the ion trajectory. This approach refines the damage modeling, producing more pronounced discontinuous damage patterns along the ion path for all crystallographic directions compared to the model that assumes all the energy accumulated in the electron-hole ensemble is delivered to the atoms.
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All authors Roman Voronkov, Danil Zainutdinov, Nikita Medvedev, Alexander E. Volkov
Materials Science
Complex crystal structure prediction using ML-enhanced multi-minima iterative genetic algorithm
Ling Tang, Weiyi Xia, Tyler J. Slade et al. (+2 more)
Current machine learning (ML) approaches for materials discovery rely heavily on known structural databases, limiting their ability to identify entirely novel structure types. In this work, we develop a multi-minima iterative genetic
algorithm (MMIGA) that integrates an artificial-neural-network machine learning (ANN-ML) interatomic potential with an iterative, metadynamics-inspired penalty scheme. We demonstrate the robustness of this method on a complex ternary La-Co-Pb system, characterized by Co-Pb immiscibility and an intricate energy landscape. The ML-enhanced MMIGA successfully predicts the ground-state Pbam structure of the recently synthesized La4Co4Pb antagonistic-pair-phase, a novel structure missed by previous database-reliant ML predictions, while also identifying multiple metastable competing phases. Additionally, we challenged the MMIGA method to predict the structure of La5CoPb2 antagonistic-pair-phase, a new compound discovered during earlier attempts to synthesize the predicted phase La3CoPb. With only knowledge of the composition, our MMIGA approach successfully predicts the orthorhombic structure of La5CoPb2, producing an exact match with the structure independently determined by x-ray diffraction. By efficiently mapping both global minimum and relevant competing metastable states, this approach provides critical theoretical insights into phase selection for novel
quantum and
magnetic materials.
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All authors Ling Tang, Weiyi Xia, Tyler J. Slade, Paul C. Canfield, Cai-Zhuang Wang
Materials Science
Geometry-Driven Magnetoelectric Coupling in Two-Dimensional Compensated Ferrimagnets
Peibo Xu, Yixuan Che, Haifeng Lv et al. (+2 more)
The magnetoelectric coupling in compensated magnets enables stray-field-free manipulation of
spin-splitting, holding great promise for spintronics, but inherently hindered by the
symmetry mismatch between spatial-inversion-broken ferroelectricity and time-reversal-broken
spin states. Here, based on a
symmetry-decoupled analysis of magnetoelectric coupling in compensated magnets, we establish a geometry-driven
spin-ferroelectric coupling mechanism in
bilayer breathing kagome
lattices. Within this
geometric framework interlocking the out-of-plane electric polarization with cooperative intralayer structural distortions, we demonstrate that polarization switching drives a deterministic reversal of the global
spin splitting. First-principles calculations on a prototype
bilayer Nb3Cl8 successfully validate this mechanism, demonstrating the switching of
spin-splitting states through an energetically feasible, asynchronous layer-by-layer transition pathway. Our proposed coupling originates from
lattice geometry and structural
symmetry, establishing a unique route toward switchable
spin splitting in compensated ferrimagnets.
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All authors Peibo Xu, Yixuan Che, Haifeng Lv, Xiaojun Wu, Jinlong Yang
Materials Science
Substrate-dependent electrical transport in individual single-walled carbon nanotubes grown across SiO$_2$ and hexagonal boron nitride
Yuanjia Liu, Taiki Inoue and Yoshihiro Kobayashi
The electronic transport properties of carbon nanotubes (CNTs) are strongly affected by their surrounding environment, making the underlying substrate a critical factor for device performance. Here, we demonstrate enhanced carrier transport of individual single-walled CNTs on hexagonal boron nitride (hBN) by directly comparing CNT channels on SiO$_2$ and hBN within the same nanotube. This within-tube comparison removes tube-to-tube variability in chirality, diameter, and defect density, allowing the intrinsic substrate effect to be evaluated more reliably. The CNTs were synthesized using gas flow-directed growth, which yields long, well-aligned CNTs without transfer processes, allowing a single nanotube to extend across different substrate regions. Multichannel field-effect transistors fabricated along an individual CNT exhibit clear ambipolar characteristics. CNT channels on hBN consistently exhibit higher field-effect mobility than those on SiO$_2$. In contrast, temperature-dependent transport near the charge neutrality point exhibits thermally activated behavior with similar activation energies (15-20 meV) on both substrates, indicating that the intrinsic small bandgap of CNTs is largely unaffected by the substrate. These results provide direct evidence that hBN enhances low-field carrier transport in CNTs and establish a foundation for the fabrication of high-performance electronics based on hBN-supported CNTs.
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Materials Science
First-principles calculations of spin-split bands in chiral hybrid organic-inorganic perovskites ($R$/$S$-PEA)PbI$_3$ and ($R$/$S$-NEA)PbI$_3$
Tetsuya Furukawa, Kazushi Nakano, Youta Suzuki et al. (+3 more)
Chiral hybrid organic-inorganic perovskites provide a promising platform for investigating the physics of chirality-driven
spin-split bands because they combine robust molecular chirality with strong
spin-orbit coupling from heavy inorganic ions. First-principles calculations including
spin-orbit coupling are performed for the one-dimensional
chiral perovskites ($R$/$S$-PEA)PbI$_3$ and ($R$/$S$-NEA)PbI$_3$ to compare their
spin-split band structures and to identify the factors controlling their differences. In ($R$/$S$-PEA)PbI$_3$, the lowest conduction bands predominantly consist of Pb orbitals, whereas in ($R$/$S$-NEA)PbI$_3$, they are formed by hybridization between Pb orbitals and the lowest unoccupied molecular orbital of NEA. Both compounds exhibit pronounced
spin splitting near the valence-band maximum and conduction-band minimum. The effective
spin splitting of the edges of the valence bands is stronger in ($R$/$S$-NEA)PbI$_3$, despite similar linear-in-$k$ splitting coefficients near the relevant high-
symmetry points. This enhancement originates from larger gaps induced by
spin-orbit coupling at high-
symmetry points and band (anti)crossings in the multiband structure. For a given molecular handedness, the PEA- and NEA-based compounds exhibit opposite
spin textures, consistent with the opposite
chiral distortions of the [PbI$_6$]$^{4-}$ octahedra and with the previously observed opposite signs of circular dichroism. Group-theoretical analysis for the nonsymmorphic space group $P2_12_12_1$ further accounts for band sticking,
symmetry-enforced degeneracies, and the disappearance of
spin polarization at specific Brillouin-zone-boundary points. These results provide a solid foundation for future studies of chirality-dependent electromagnetic responses, including circular dichroism, in
chiral hybrid organic-inorganic perovskites.
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All authors Tetsuya Furukawa, Kazushi Nakano, Youta Suzuki, Takumi Kaneko, Ayumi Ishii, Tetsuaki Itou
Materials Science · Cross-listed from cs.AI
Graph-Native Reinforcement Learning Enables Traceable Scientific Hypothesis Generation through Conceptual Recombination
Subhadeep Pal, Shashwat Sourav, Tirthankar Ghosal et al. (+1 more)
Accelerating materials discovery requires AI systems that can generate scientifically valid hypotheses through multi-step, domain-grounded
reasoning. Standard large
language models often produce fluent but weakly traceable responses to open-ended materials design problems, making it difficult to determine whether final answers are supported by coherent intermediate
reasoning. We develop Graph-PRefLexOR, a family of graph-native
reasoning models fine-tuned with Group Relative Policy Optimization (GRPO) to organize
reasoning into explicit phases for mechanism exploration, graph construction, pattern extraction, and hypothesis synthesis. This design links neural
language generation with symbolic relational structure, enabling causal connections to be constructed, inspected, and reused. On 100 open-ended questions from materials science and mechanics literature, Graph-PRefLexOR achieves 40-65% improvements over corresponding base models, with the largest gains in
reasoning traceability.
Embedding analyses show broader semantic exploration and approximately 2-3 times greater semantic diversity than baselines. Semantic backtracking and layer-wise hidden-state analyses further show stronger
alignment between structured
reasoning and final answers. Finally, test-time graph expansion reveals that additional compute primarily increases long-range conceptual recombination within a bounded semantic space, rather than simply expanding semantic coverage. These results establish graph-native reinforcement learning as a pathway toward interpretable AI systems for scientific hypothesis generation in materials design and other scientific applications.
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All authors Subhadeep Pal, Shashwat Sourav, Tirthankar Ghosal, Markus J. Buehler
Materials Science
Strengthening and interface-mediated plastic co-deformation in an ultrafine Cr-Ni eutectic: A nanomechanical investigation
Arkajit Ghosh, Mustafa Tobah, Jianing Zhou et al. (+2 more)
Ultrafine eutectic
heterostructures provide a stringent test of plasticity in high-strength materials, where deformation must be accommodated through interfaces and strain gradients. Room temperature ductility is typically limited by premature fracture of the hard phase, leaving open the fundamental questions regarding the interface spacing, atomic structure and local chemistry that enable plastic co-deformation. Here we address this question using a model system of Cr-Ni binary
alloy, processed via electron-beam powder bed fusion that produces a lamellar eutectic microstructure of Cr-rich BCC and Ni-rich FCC phases, with an average interlamellar spacing of ~450 nm. Atomic-resolution STEM revealed a stepped semi-coherent FCC/BCC interface with the Kurdjumov-Sachs orientation relationship and Ni-enrichment confined to a few atomic planes on the BCC side. In situ micro-scale compression and tension tests in SEM demonstrate high flow stresses coupled with large plastic strains without cracking, indicating stable accommodation of plastic incompatibility. Correlative TEM/HR-STEM establishes a deformation sequence: initial plasticity is dominated by strain-gradient driven dislocation accumulation in the FCC lamellae adjacent to interfaces, followed by deformation twinning in FCC and local interfacial shear and reorientation. The BCC phase subsequently develops a high density of mobile dislocations. Atomistic modeling has been employed to understand the influence of the FCC/BCC interface atomic structure and chemistry on the slip activation in the hard phase. These findings show that nanoscale confinement, stepped K-S interfacial structure, and interfacial chemistry collectively promote dislocation glide in a hard phase below its monolithic brittle to ductile transition temperature, and plastic codeformation at high flow strengths.
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All authors Arkajit Ghosh, Mustafa Tobah, Jianing Zhou, Jian Wang, Amit Misra
Materials Science
Two-dimensional vertically polarized Hg3AsSe4I monolayer for efficient photocatalytic water-splitting: promoting carrier separation by intrinsic electric field and Rashba effect
Xinfeng Chen, Wenchao Shan, Fengfeng Ye et al. (+1 more)
Efficient separation of photo-excited electron-hole pairs is essential for developing the high performance photocatalysts towards light-driven water-splitting applications. To this end, pho tocatalytic performances of two-dimensional (2D) semiconducting ferroelectric (FE) materials with out-of-plane polarizations have been extensively explored. However, out-of-plane polarizations in 2D FE materials are susceptible to the critical thickness limitation and can be easily compensated by surface adsorbates. On the other hand, 2D vertically polarized materials with stable and ir reversible out-of-plane polarizations may overcome the critical thickness limitation, enabling the practical advantage for spatial separation of photo-excited electron-hole pairs during the photo catalytic reactions. In the current work, 2D vertically polarized Hg3AsSe4I, an experimentally synthesized van der Waals (vdW) layered material, has been systematically investigated as a high performance 2D photocatalyst. Owing to its semiconducting band gap suitable for visible-light absorption, high carrier mobility, and desirable band edge
alignment ideally matching water reduc tion and oxidation potentials, Hg3AsSe4I monolayer fulfills both optical and electronic prerequisites for photocatalytic water-splitting reactions. Besides the stable vertical polarization able to persist in Hg3AsSe4I monolayer, the dual mechanism for efficient separation of photo-excited carriers has also been demonstrated. Rashba
spin-orbit coupling (SOC) of large strength emerges within 2D Hg3AsSe4I, splitting the band edges into
spin-resolved band branches with unique
spin-momentum locking characters.........
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All authors Xinfeng Chen, Wenchao Shan, Fengfeng Ye, Gaoyang Gou
Materials Science
Vanadium superconducting microwave resonators on silicon wafers
Y. Fujita, Y. Urade, Y. Hibino et al. (+4 more)
Understanding the correlation between material properties and microwave losses in superconducting films is a crucial subject for developing low-loss materials for
quantum circuits. We focus on vanadium (V) as a novel material for superconducting
quantum devices and discuss loss in V films in relation to their structural properties. Using a sputtering method, we grow four V-film structures on (001)-oriented Si wafers, employing Nb and Ta as the buffer and capping layer materials, respectively: Nb/V/Ta, Nb/V, V/Ta, and V. X-ray diffraction and atomic force microscopy reveal that the V films grown on the Nb buffer layers have higher uniformity of
lattice orientation and smaller grain size than that directly grown on the Si wafer. Coplanar waveguide resonators are fabricated from the four V-film structures, and averaged
photon number ($\langle n_{\rm ph} \rangle$) dependences of internal quality factor ($Q_{\rm int}$) are obtained by performing microwave measurements. By analyzing the obtained $Q_{\rm int}$ vs $\langle n_{\rm ph} \rangle$, it is found that loss at the V surface is dominated by $\langle n_{\rm ph} \rangle$-independent non-two-level-system (non-TLS) losses, which can be mitigated by introducing the Ta capping layer. Furthermore, the V films on the Nb buffer layers exhibit lower $Q_{\rm int}$ in the $\langle n_{\rm ph} \rangle$ range from 10$^{0}$ to 10$^{6}$ and higher non-TLS loss than that directly grown on Si wafers, even though the former has higher
lattice-orientation uniformity than the latter. Origins of these trends might be relevant to V
oxides, of which presence at surfaces and grain boundaries in bulk regions in the V resonators is suggested by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy, and/or V hydrides.
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All authors Y. Fujita, Y. Urade, Y. Hibino, M. Tsujimoto, K. Inomata, G. Fujii, W. Mizubayashi
Materials Science
Prediction of coherent interfaces between diamond and clathrate structures
Eva Pospíšilová and Marek Mihalkovič
Diamond (or its binary zincblende variant)-type structure can form coherent interface with clathrate type II via the common transitional layer known previously as a $(3\times 3)$-dimer-stacking fault (DS) reconstruction of the (111)-diamond surface. The generic $\sim 11\%$
lattice misfit can be eliminated in multicomponent
heterostructures such as Ge(diamond)/CsSn(clathrate) or InN(zincblende)/Ge(clathrate). Interface models subjected to ab-initio molecular dynamics annealing are stable up to the temperatures approaching melting point of the constituent systems, and in some studied cases the diamond/clathrate bonding is stronger than the intra-clathrate bonding, as evidenced by simulated crack experiments. Composition-calibrated
lattice-matching can stabilize even metastable clathrates as epitaxially grown films on the diamond/zincblende substrate.
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Materials Science
The BiP-PRISM algorithm for fast and scalable core-loss STEM-EELS simulations
Philipp Pelz
Quantitative interpretation of atomic-resolution STEM-EELS requires dynamical simulation of the electron probe before and after core-loss transitions, which is computationally expensive. While the PRISM
algorithm accelerates this by reusing scattering
matrices, we introduce beam partitioning for both the probe-forming ($\mathcal{S}_1$) and detector-propagating ($\mathcal{S}_2$) PRISM
matrices to further reduce computational and
memory costs. Each
matrix is calculated on a sparse set of parent beams and reconstructed via natural-neighbor interpolation locally at the ionized atom. A locality result demonstrates that the total error is governed entirely by this on-atom reconstruction error. The resulting BiP-PRISM
algorithm removes per-scan exit wave propagation and significantly reduces
memory requirements, enabling full-resolution elemental mapping, 4D cubes, and momentum-resolved qEELS on consumer-grade GPUs. We characterize the approximation's validity regime and demonstrate the simulation of a
multimodal five-edge
oxide-interface map and an FePt nanoparticle Fe-L map at 5x
memory reduction, showing that the
algorithm achieves high accuracy with significantly lower computational demands.
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Materials Science
Atomic Cluster Expansion Potentials for Screw Dislocations in BCC Refractory Metals
Lei Zhang and Francesco Maresca
Accurate atomistic modeling of screw dislocations in body-centered cubic (bcc) metals remains challenging because their plasticity is governed by a complex dislocation glide behavior due to their compact three-fold symmetric core structure and a strongly temperature-dependent flow stress induced by the large Peierls barrier. In the context of group 6 (V, Nb, Ta) and group 5 (Mo, W) refractory metals (RMs), both classical interatomic potentials and some machine learning potentials consistently fail to reproduce density functional theory (DFT) Peierls barriers and the glide plane. Here, we developed an array of atomic cluster expansion (ACE) potentials for these RMs by extending an existing DFT database. The developed ACE potentials significantly improve the description of screw dislocation properties, achieving near-DFT accuracy for Mo and W and substantial improvement for V, Nb, and Ta. The results show that transferability to screw dislocation behavior depends sensitively on both database composition and element-specific energetics, and that achieving a single-humped Peierls barrier alone is not a sufficient validation metric for accurate prediction of dislocation glide. For Nb, Mo, and W, the developed ACE models also enable reliable calculation of kink-pair activation enthalpies, which are well described by both Kocks' law and a line-tension model.
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Materials Science · Cross-listed from physics.optics
Near-Field Characterisation of Guided Modes in WS2 Nanobeams and Quasi-Bulk Crystals
Zara S. Taylor, Luke M. Hallacy, Xuerong Hu et al. (+7 more)
The exceptionally high in-plane refractive index, low sub-bandgap absorption, and strong optical anisotropy of WS2 make it a promising material platform for next-generation integrated
circuits for nanophotonics. Its layered van der Waals structure further enables heterogeneous integration with silicon photonics and emerging two-dimensional optoelectronic materials. However, despite increasing interest in the waveguiding properties of WS2, experimental studies of wavelength-dependent modal confinement and attenuation remain limited. Additionally, though the extinction coefficient of WS2 is expected to be near-negligible beneath the bandgap, reported values span orders of magnitude, leading to large uncertainty in predicted modal decay lengths and wafer-scale integration feasibility. To resolve these ambiguities we perform hyperspectral cavity-enhanced imaging, determining high-resolution upper and lower bounds on the extinction coefficient of WS2 within the visible-NIR edge. We further employ scattering-type scanning near-field optical microscopy (s-SNOM) to probe TE0, TM0, and higher-order modes in both quasi-bulk and nanobeam WS2 waveguides across the 800-1400 nm spectral range, enabling identification of mode-specific trends in wavevector dispersion and loss. This work simultaneously assesses s-SNOM as a probe of waveguide performance, and we find that while absolute loss values depend on measurement geometry, s-SNOM reliably captures relative modal trends and provides upper bounds on propagation loss, supporting its use as a diagnostic tool for anisotropic waveguides. We further identify significant artefacts in nanobeam measurements arising from transverse interference and spatial sampling effects when the structure size approaches the excitation wavelength, which can shift extracted effective indices by up to 0.25.
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All authors Zara S. Taylor, Luke M. Hallacy, Xuerong Hu, Oliver T. Williams, Simone Strohmair, Fabian Felixberger, Alexander J. Knight, Timothy Chester-Parsons, Luke R. Wilson, Alexander I. Tartakovskii
Materials Science · Cross-listed from physics.ins-det
In-Situ Polarimetry in Collimated Magneto-Infrared Spectroscopy System
Zeping Shi, Wenbin Wu, Zhiwei Zhang et al. (+14 more)
Magneto-infrared spectroscopy under strong
magnetic fields provides a powerful probe of Landau quantization and field-induced collective excitations, yet its full potential has long been constrained by the lack of in-situ polarization control, because the highly divergent infrared beam propagating through narrow light tubes undergoes multiple wall reflections, leading to severe polarization degradation. Here we report a collimated magneto-infrared spectroscopy system that integrates continuous in-situ polarimetry. The system employs incident and exit collimation chambers forming a Kepler type optical architecture, which converts the large-aperture FTIR output into a low-divergence beam and strongly suppresses multi-reflection trajectories inside long gold-plated light tubes, thereby enhancing both optical throughput and polarization fidelity. A remotely controlled polarization module, consisting of an automated linear polarizer and a switchable Fresnel rhomb positioned entirely outside the high-field region, enables continuous in-situ tuning between linear, circular, and arbitrary elliptical polarization states without thermal cycling, manual realignment, or breaking
vacuum. Interchangeable compact focusing modules further support Faraday and Voigt geometries in both transmission and reflection experiments within a 50 mm magnet bore, providing efficient beam focusing and signal collection while maintaining polarization fidelity. The setup achieves a minimum root-mean-square noise of 0.0033%, an average noise of 0.0082%, and a linear polarization extinction ratio up to 40:1. We demonstrate the capability through continuous in-situ linear polarimetry and broadband circular polarimetry in the magneto-infrared spectroscopy of various single
crystals. This platform establishes a robust experimental framework for in-situ polarization-resolved magneto-infrared spectroscopy.
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All authors Zeping Shi, Wenbin Wu, Zhiwei Zhang, Yuhan Du, Chenyao Xu, Congming Hao, Xiangyu Jiang, Xin Chen, Guangyi Wang, Mingsen Zhou, Chunhui Pan, Wei Lu, Hao Shen, Haifeng Pan, Zhenrong Sun, Junhao Chu, Xiang Yuan
Materials Science · Cross-listed from cond-mat.mes-hall
Facet-selective ballistic supercurrent in a weak topological insulator
Prasanna Rout, Ankit Khola, Lalit Pandey et al. (+9 more)
Topological superconductivity is widely pursued by inducing superconducting correlations in topologically protected boundary states. In two dimensions, this strategy has been realized using one-dimensional topological edge modes, but in three-dimensional
crystals, spatially separated surface supercurrents confined to selected facets have not yet been achieved. Here we demonstrate facet-selective ballistic supercurrent in Josephson junctions based on the weak topological
insulator ZrTe<sub>5</sub>. Superconducting
quantum interferometry reveals SQUID-like critical current oscillations with flux-
quantum periodicity, establishing that the supercurrent is spatially concentrated on specific crystallographic facets that host gapless topological surface states. Rotating the
magnetic field yields markedly distinct interference patterns, linking the supercurrent distribution to the underlying bulk
topology. The exponential temperature dependence of the critical current and triangular interference lobes provide signatures of ballistic transport due to high-transmission topological channels. These results establish weak topological
insulators as a platform for facet-resolved superconducting devices and higher-order topological superconductivity.
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All authors Prasanna Rout, Ankit Khola, Lalit Pandey, Paolo Sessi, Xiaochun Huang, Ivo Cools, S. Galeski, Matthias Bode, Johan Åkerman, Floriana Lombardi, Thilo Bauch, Saroj P. Dash
Materials Science · Cross-listed from cond-mat.mes-hall
Spinterface-like mechanism of the chirality-induced spin selectivity in donor chiral-bridge acceptor complexes
Subhajit Sarkar, Oliver L. A. Monti and Yonatan Dubi
The chirality-induced
spin selectivity (CISS) effect has been invoked to explain recent reports of differences in the time-resolved EPR signals between
chiral and achiral molecules. However, the microscopic origin of these differences and their connection to CISS remains contested, particularly since these systems lack a metal interface. Here we introduce an intramolecular spinterface-like mechanism that naturally arises within donor-
chiral bridge-acceptor (D–$\chi$B–A) complexes and quantitatively reproduces experimentally reported observed
spin polarization in time-resolved EPR studies. In our two-electron Lindblad model, the photoexcited charge-transfer electron traversing the
chiral bridge exchanges with the residual donor electron, which acts as a localized
magnetic moment analogous to an induced
magnetic moment on an electrode surface. The resulting through-bridge charge current produces an effective solenoidal field at the donor–bridge interface, breaking
spin degeneracy and directional
symmetry, thus enabling
spin-selective transport without invoking intrinsic
spin-orbit coupling on the bridge. We show that the interplay between this current-induced field, donor thermalization (which breaks time-reversal
symmetry), and bridge
spin mixing yields tens-of-percent polarization over realistic experimental conditions and charge-transfer time scales, matching reported CISS signatures in triads and DNA hairpins. By explicitly resolving the dependence on solenoidal coupling strength, temperature, and
spin-mixing rates, the model identifies the regime in which internal spinterfaces can generate robust CISS-like
spin filtering. These findings demonstrate that CISS-like signals in isolated D–$\chi$B–A complexes are fully compatible with a spinterface mechanism, providing a unified conceptual framework for interpreting both device-based and molecule-internal CISS platforms.
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Materials Science · Cross-listed from physics.optics
Self-selected phase-matched second harmonic generation in nonlinear optical materials: from phenomenon to applications
Niklas Dömer, Tobias Hehemann, Felix Sauerwein et al. (+3 more)
Self-selected phase-matched second harmonic generation is introduced as an all-optical probe of refractive-index dispersion in birefringent nonlinear optical materials. Rather than requiring wavelength or angular tuning, the exposure with a spectrally broad, intense ultrashort pulse allows the material to self-select the fundamental spectral component that satisfies the type-I noncritical phase-matching condition. This produces a narrow peak in the second harmonic spectrum whose position is governed by the refractive indices and is therefore highly sensitive to material parameters that affect the optical dispersion. We demonstrate the application of this phenomenon for the optical inspection of stoichiometry and temperature gradients in technologically relevant lithium niobate, as well as composition inhomogeneities in newly grown lithium niobate-tantalate solid solutions. These results establish self-selected phase-matched second harmonic generation as a rapid, non-contact method for inspecting nonlinear optical materials, with potential relevance for bulk
crystals, wafers, and thin-film platforms.
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All authors Niklas Dömer, Tobias Hehemann, Felix Sauerwein, Sebastian Inckemann, Steffen Ganschow, Mirco Imlau