Materials Science · Cross-listed from physics.comp-ph
Resonance Statistics -Informed Fitting Applied to Automated Cross Section Evaluation
William Fritsch, Noah Walton, Justin Loring et al. (+5 more)
This work investigates the use of resonance statistics for resonance evaluation to inform
spin group assignment and an alternative fitting objective function beyond the commonly used chi-squared statistic. Resonance statistics -informed methods are applied to the automated resonance fitting framework, developed by N. Walton et al. In this automated framework, the utility of resonance statistics is largely unexplored. The new resonance statistics -informed
spin group shuffling
algorithm reduces
spin group frequency bias seen in the base fitting
algorithm. Although resonance statistics -informed optimization produces negligible changes in pointwise cross section agreement, it significantly improves consistency with Wigner level-spacing statistics and stabilizes the fitted resonance density in the presence of model imperfections.
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All authors William Fritsch, Noah Walton, Justin Loring, Jacob Forbes, Oleksii Zivenko, Aaron Clark, Elan Park-Bernstein, Vladimir Sobes
Materials Science · Cross-listed from physics.comp-ph
From Code to Figure: A FAIR-Aligned Data Provenance Chain for Reproducible Simulation Research in Numerical Physics
Markus Uehlein, Tobias Held, Christopher Seibel et al. (+3 more)
Computational physics increasingly depends on large simulation
datasets generated by software that remains under active development for many years. In such settings, reproducibility requires not only well documented data but also explicit links between code versions, simulation inputs, generated outputs, analysis steps, and published figures. Here, we present an integrated workflow for reproducible and FAIR-aligned simulation research in numerical physics. We describe how version control, code review, automated testing, structured logging, metadata-rich output, and standardized post-processing can be combined to support traceability from software development to publication. The presented concepts demonstrated for one particular simulation framework are broadly applicable to computational physics and other data-intensive areas of scientific computing.
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All authors Markus Uehlein, Tobias Held, Christopher Seibel, Lukas G. Jonda, Baerbel Rethfeld, Sebastian T. Weber
Materials Science
Intrinsic grain-size gradients upon grain growth near a free surface
Jing Tang, Runlu Yan, Donglan Zhang et al. (+5 more)
Grain growth fundamentally shapes the microstructure of crystalline materials upon annealing, affecting their overall mechanical and functional properties. Recently, it has been rationalized that grain growth in polycrystals does not result solely from weighted
curvature flow, but elastic effects (intrinsic stress) arised from shear coupling also need to be taken into account. We characterize and examine the effect of free surfaces on grain growth kinetics of high-purity, bulk polycrystalline nickel. By analyzing the microstructural
evolution on cross sections of 1 mm thick specimens from the surface to the interior, as well as through in-plane investigations on specimens with varying thickness (1 mm, 40 $\mu$m, and 10 $\mu$m), an intrinsic grain-size gradient was identified, characterized by a gradual increase in grain size towards the interior. Interestingly, this grading was not restricted to the very surface but continued to depths of five to ten layers of grains, where effects from thermal grooves are considered negligible. We demonstrate that this behavior is significantly affected by elastic relaxation at the free surface, which alters the internal stress fields generated by shear-coupled grain boundary migration. These findings emphasize the relevance of free surfaces to the microstructural
evolution of polycrystal.
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All authors Jing Tang, Runlu Yan, Donglan Zhang, Ronald Schnitzer, Lorenz Romaner, Marlene Kapp, Marco Salvalaglio, Oliver Renk
Materials Science · Cross-listed from physics.optics
Revealing full molecular orientation distributions in organic thin films by nonlinear polarimetry
Pierre-Luc Thériault, Emna Azek, Gabriel Juteau et al. (+7 more)
The performance of organic optoelectronic devices is critically dependent on how molecules orient within organic thin films. Yet, standard characterization techniques only reveal the first and second moments of the molecular orientation distribution. This limitation obscures the true molecular arrangement, as diverse distributions can yield identical low-order averages while exhibiting distinct functional properties. Here, we bridge this gap by combining multi-harmonic nonlinear polarimetry (second, third, and fourth harmonic) with the Maximum
Entropy Method to reconstruct the probability distribution without any a priori assumptions. This allows us to resolve features in the distribution such as asymmetry and bimodality, that remain invisible to conventional probes. Furthermore, we use this method to
benchmark molecular dynamics simulations, revealing that these simulations often fail to capture the complex distribution despite correctly predicting the first and second moments. This work transforms molecular orientation from an inferred average into a precise observable, establishing essential validation standards for predictive material design.
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All authors Pierre-Luc Thériault, Emna Azek, Gabriel Juteau, Anagh Mukherjee, Heorhii V. Humeniuk, Zhechang He, Alexandre Malinge, Dmytro F. Perepichka, Lena Simine, Stéphane Kéna-Cohen
Materials Science
Two New Molecular Nitrogen Phases near Megabar Pressures
Alexander F. Goncharov, Elena Bykova, Iskander Batyrev et al. (+7 more)
Molecular nitrogen exhibits remarkable structural diversity near the polymeric transition, where multiple phases are metastable. Here, we report two new molecular phases. The first, $t\zeta$-N$_2$, is a polytype of monoclinic $C2/c$ $\zeta$-N$_2$, characterized by a tripled $c$ axis and 96 atoms per unit
cell. The second, $\xi$-N$_2$, is a previously unreported hexagonal phase ($P6cc$) containing 112 atoms per unit
cell. Both phases were synthesized in a diamond anvil
cell by
laser heating $\zeta$-N$_2$ to 1800–2500~K at pressures of 78–98~GPa. Their
crystal structures were determined using single-
crystal X-ray diffraction, corroborated by Raman spectroscopy, and supported by first-principles calculations. The $t\zeta$-N$_2$ phase likely corresponds to the previously reported $\kappa$-N$_2$ phase.
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All authors Alexander F. Goncharov, Elena Bykova, Iskander Batyrev, Maxim Bykov, Huawei Chen, William Palfey, Mahmood Mohammad, Stella Chariton, Vitali Prakapenka, Jesse S. Smith
Materials Science · Cross-listed from physics.atom-ph
Continuous-wave laser absorption spectroscopy of the Thorium-229 nucleus
I. Morawetz, T. Riebner, L. Toscani De Col et al. (+17 more)
A low-energy
nuclear transition in the isotope thorium-229 has been excited in thorium-doped
crystals with
laser light. This opens the perspective towards a highly stable and robust solid-state optical
nuclear clock. The required
laser radiation at 148 nm wavelength has so far been produced using pulsed
laser systems where only a small fraction of the incident
photons has been resonant with the narrow
nuclear transition. Here we show that the
nuclear resonance can be excited with a continuous-wave narrow-bandwidth
laser source with a power of less than 1 nW, and that the resonance signal can be detected in absorption rather than in fluorescence. This eliminates the slow
nuclear fluorescence decay from the detection process and offers a considerable advantage for clock operation through fast signal acquisition. The VUV
laser source is based on three sequential frequency doublings, starting from a diode
laser at 1187 nm that is well suited for linewidth narrowing and for frequency comparisons with optical atomic clocks. We use absorption spectroscopy for the quantitative characterization of two different Th-centers in calcium fluoride
crystal and measure the isomeric shift between them. One of the centers shows a very small static electric
crystal field gradient 0.1 V/$\r{A}^2$, to be compared to gradients in the range of 100 V/$\r{A}^2$ observed earlier. This indicates a center with high
symmetry of the ions surrounding the Th
nucleus, promising
nuclear resonance lines that are nearly independent of the
lattice spacing.
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All authors I. Morawetz, T. Riebner, L. Toscani De Col, F. Schneider, N. Sempelmann, F. Schaden, M. Bartokos, G. A. Kazakov, S. Lahs, K. Beeks, B. Gerstenecker, A. Grüneis, M. Pimon, T. Schumm, V. Lal, G. Zitzer, V. Petrov, J. Tiedau, M. V. Okhapkin, E. Peik
Materials Science · Cross-listed from cond-mat.supr-con
Ultrafast Magneto-Pressure Spectroscopy and Control of Correlated Phases in a Trilayer Nickelate
Zhi Xiang Chong, Joong-Mok Park, Shuyuan Huyan et al. (+10 more)
Ultrafast spectroscopy under simultaneous high pressure and
magnetic field provides a versatile approach for investigating pressure-driven electronic instabilities and correlated phases, and for probing potential bulk superconducting behavior under extreme conditions. However, such an experimental platform has yet to be implemented, standing as a roadblock to a fuller understanding of nonequilibrium superconductivity and
vortex-controlled quasi-particle (QP) dynamics. Here, we bridge this capability gap by developing high pressure (up to 40 GPa), high
magnetic field (up to 7 T), cryogenic (down to 5 K) femtosecond spectroscopy, and using it to probe magneto-pressure
evolution of quasiparticle dynamics in the trilayer nickelate $\mathrm{Pr}_4\mathrm{Ni}_3\mathrm{O}_{10}$. We observe pronounced critical slowing down of QP relaxation at the charge-density-wave transition, which collapses under applied pressure. At higher pressures, the relaxation instead lengthens at low temperature, consistent with incipient superconducting correlations. However, the negligibel
magnetic-field-dependence up to 7~T and absence of
vortex-induced pre-bottleneck dynamics–robust signatures observed in our controlled bulk superconducting samples–indicates that any superconducting state under the present pressure conditions is likely non-bulk, filamentary, or strongly inhomogeneous. The magneto-pressure ultrafast capability opens a new avenue for resolving outstanding questions surrounding pressure-induced superconductivity and intertwined orders in correlated
quantum materials.
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All authors Zhi Xiang Chong, Joong-Mok Park, Shuyuan Huyan, Avinash Khatri, Martin Mootz, Xinglong Chen, Daniel P. Phelan, Liang Luo, Ilias E. Perakis, J. F. Mitchell, Sergey L. Bud'ko, Paul C. Canfield, Jigang Wang
Materials Science
Atomistic Mechanisms of Stress-Dependent Molten Salt Corrosion in NiCr Alloys
Hamdy Arkoub, Jia-Hong Ke and Miaomiao Jin
Ni-based structural
alloys in molten salt environments often experience simultaneous mechanical loading and corrosive attack, yet the mechanisms governing stress-corrosion interactions remain unclear. Prior studies largely emphasize tensile stress, while the role of compressive stress has received limited
attention. Here, reactive molecular dynamics simulations are used to investigate the coupled effects of applied strain and corrosion in Ni$_{0.75}$Cr$_{0.25}$ exposed to molten FLiNaK at 800$^\circ$C. A $\Sigma5(210)$ grain boundary model is subjected to tensile (+4%) to compressive (-4%) uniaxial strains, and corrosion behavior is evaluated through fluorine adsorption, charge redistribution, and grain boundary
evolution. Tensile strain accelerates intergranular corrosion by reducing local atomic packing through elastic dilation and increasing excess free volume at the grain boundary, which enhances atomic mobility and salt infiltration. In contrast, compressive strain suppresses corrosion by promoting the formation of a ridge-like surface layer along the grain boundary, limiting salt access to the underlying
alloy. These results provide atomistic insight into how stress states influence grain boundary corrosion in molten salts.
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Materials Science
Bridging Atomistic and Continuum Descriptions of Nanoscale Dislocation Loops in Tungsten
Joseph Duque Lopez, Sergei Dudarev, James Kermode et al. (+1 more)
In order to predict the long-term effects of irradiation on the material properties of tungsten, a continuum approach to simulating the interactions of dislocation loops, which arise from radiation damage, is proposed. Continuum models of the displacement, strain and stress fields produced by dislocation loops exhibit unphysical singularities near the defect core, but are thought to accurately capture atomistic displacements in the far-field. A linear elastic model of nanoscale dislocation loops in tungsten is developed, and the model is verified using atomistic simulations to ensure that the model is informed by lower-length scale phenomena such that the physics of the problem is correctly captured. We discuss the model and its advantages, and show that predictions produced by atomistic simulations do indeed agree well with the far-field behaviour of the continuum model when dislocation loops are far from material boundaries. In particular, we robustly demonstrate that the decay rate of atomistic results and continuum results coincide with one another, and show that the results converge as the size of the atomistic simulations approach the far-field limit.
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All authors Joseph Duque Lopez, Sergei Dudarev, James Kermode, Thomas Hudson
Materials Science
ChemGraph-XANES: An Agentic Framework for XANES Simulation and Curation
Vitor F. Grizzi, Thang Duc Pham, Luke N. Pretzie et al. (+3 more)
Computational X-ray absorption near-edge structure (XANES) is widely used to interpret local coordination environments, oxidation states, and electronic structure, but large computational campaigns are often limited by workflow complexity. We present ChemGraph-XANES, a large
language model (LLM)-based agentic framework that combines documentation-grounded parameter
retrieval via
retrieval-augmented generation (RAG), schema-constrained tool execution, deterministic FDMNES input generation, Parsl-backed execution, and provenance-aware data curation. Scripted and natural-
language interfaces share a common scientific backend for structure handling, parameterization, execution, spectral extraction, and optional post-processing. We evaluate three workflow modes: documentation-grounded parameter propagation, structure-file-based execution, and composition-based execution from a chemistry-level request. Repeated trials yielded end-to-end completion in 10/10 composition-based runs, 10/10 structure-file-based runs, and 9/10 documentation-grounded RAG runs. In every RAG run, the energy-grid specification retrieved from the FDMNES manual was correctly propagated, with the single end-to-end failure occurring downstream during multi-structure handling. In a separate task-parallel demonstration, the framework retrieved 21 TiO$_2$ structures from the Materials Project and submitted one FDMNES calculation per structure. All calculations completed successfully, with Parsl distributing the independent tasks across the user-configured worker pool. Together, these results show that ChemGraph-XANES provides a constrained and reproducible orchestration layer for computational spectroscopy, supporting consistent execution of representative tasks, documentation-linked parameter selection, and task-parallel generation of structure-linked XANES collections.
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All authors Vitor F. Grizzi, Thang Duc Pham, Luke N. Pretzie, Jiayi Xu, Murat Keceli, Cong Liu
Materials Science · Cross-listed from cond-mat.mes-hall
Hopping-Mediated Charge Transport in Graphene Beyond the Ballistic Regime
J. P. Dadario Pereira, Raphael Tromer, Luiz A. Ribeiro Junior et al. (+1 more)
We present a trajectory-resolved framework for charge transport in
graphene and related two-dimensional carbon systems beyond the ideal ballistic and fully coherent limits. Transport is described by kinetic Monte Carlo hopping on a predefined atomic
lattice, allowing the combined treatment of disorder, thermal activation, and external fields. Current and effective transmittance are extracted directly from
stochastic carrier trajectories, without phenomenological transport coefficients. We apply the method to
graphene under bias voltage (0-0.10 V), temperature (300-900 K),
magnetic field (0-10 T), in-plane strain (2-10%, uniaxial and biaxial), and vacancy concentration (0-10%). Pristine
graphene shows an almost ohmic response, with currents of about 7-8 uA, effective transmittance near 0.98-1.00, and conductance of about (5.8-7.8) x 10^-5 S at 0.10 V, depending on direction. Vacancies strongly suppress transport, reducing transmittance to about 0.45-0.75 at 10% vacancy. Higher temperature accelerates hopping and partly restores transport, but cannot overcome severe connectivity loss.
Magnetic fields further reduce transport, especially in disordered networks. The framework provides a unified computational scheme for realistic two-dimensional carbon materials and also yields
diffusion coefficients and effective mobilities from carrier displacements and transit times.
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All authors J. P. Dadario Pereira, Raphael Tromer, Luiz A. Ribeiro Junior, Douglas S. Galvao
Materials Science
Laser-written reconfigurable energy landscapes and programmable Moiré spin textures
Matteo Panzeri, Piero Florio, Davide Girardi et al. (+18 more)
Magnetic textures are central to emerging spintronic and unconventional computing technologies due to their rich dynamics, topological properties and nanoscale dimensions. A major challenge remains achieving tunable, reversible, and spatially resolved control over these textures and their
evolution as a function of external stimuli, by spatially reprogramming the
magnetic energy landscape that governs their nucleation and stability. Here, we exploit a focused
laser-assisted local field cooling technique that establishes a fast, non-contact and scalable platform for grayscale
spin texture engineering. By non-destructively controlling the exchange-bias anisotropy with nanoscale resolution in thin-film
heterostructures, this approach enables grayscale, reprogrammable control of the local energy profile, which we use to create
magnetic patterns with highly controlled hysteresis, field-dependent readability and tunable switching thresholds. Leveraging this capability, we demonstrate information encoding with
magnetic field-gated readability, and artificial
spin metamaterials, stabilizing
spin lattices with field-reconfigurable
symmetries and creating artificial Moiré
spin textures via the
geometric superposition of twisted
magnetic potentials. These results establish a versatile, reprogrammable platform that bridges the gap between application-oriented
magnetic memory and fundamental studies of emergent order in artificial
lattices.
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All authors Matteo Panzeri, Piero Florio, Davide Girardi, Joseba Urrestarazu, Giacomo Sala, Nicola Pellizzi, Matteo Vitali, Marco Madami, Luca Ciaccarini Mavilla, Silvia Tacchi, Elisa Riedo, Andrea Meo, Vito Puliafito, Mario Carpentieri, Riccardo Tomasello, Efe Ersoy, Kai Wagner, Patrick Maletinsky, Olivier Boulle, Edoardo Albisetti, Daniela Petti
Materials Science
Formation of photoinduced space-charge field during in-bulk domain creation by femtosecond NIR laser irradiation in MgO:LN crystals
I. A. Kipenko, D. A. Zorikhin, A. R. Akhmatkhanov et al. (+1 more)
We have studied the domain switching under NIR fs-
laser irradiation in MgO:LN single
crystals with special
attention to the relative positions of the light-induced domains, microtracks and regions with modified refractive index in the vicinity of the focusing point. The optical imaging along X direction of the irradiated sample demonstrated the narrow microtracks and the lens-shaped regions ("lenses") located in the vicinity of the microtracks. The relative positions of light-induced microtracks, domains and lenses were revealed by overlapping of their images. We have found that the domain envelops the microtrack and partially intersects with the lens. The temperature stability of all light-induced objects during annealing was studied. It was shown that the local modification of the refractive index disappeared irreversibly while the microtrack and domain remain unchanged. The obtained local modification of the refractive index has been considered as a result of the photorefractive effect. The disappearance of the lens after annealing is caused by bulk screening of the photoinduced space-charge field by increased bulk conductivity. The generation of photovoltaic field by tightly focused NIR fs-
laser irradiation close to the focusing point is reported for the first time to the authors' knowledge. It should be noted that in LN the photovoltaic field is codirectional with spontaneous polarization and thus cannot switch the polarization. However, it is possible in ferroelectrics with the opposite direction of the photovoltaic field and low value of threshold field. The revealed effect can be utilized for creation of 3D nonlinear photonic
crystals by in-bulk domain engineering.
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All authors I. A. Kipenko, D. A. Zorikhin, A. R. Akhmatkhanov, V. Ya. Shur
Materials Science
Mircomechanical insights into unconstrained grain boundary sliding
Divya Sri Bandla, Subin Lee and Christoph Kirchlechner
Grain boundary sliding (GBS) is a key deformation mechanism at high homologous temperatures in polycrystalline materials, however, its intrinsic behavior is often obscured by additional strain accommodation processes. In this study, dislocation-mediated unconstrained GBS was investigated using Ni bicrystal micropillars containing a single high-angle grain boundary. Micropillar compression tests were conducted over a temperature range from room temperature to $600\,^{\circ}\mathrm{C}$ and strain rates between $5\times10^{-4}$ and $10^{-1}\,\mathrm{s}^{-1}$. By comparing bicrystal and single-
crystal responses, the intrinsic contribution of GBS was isolated. The strain-rate sensitivity remained low (SRS $\approx 0.034 \pm 0.017$), comparable to room temperature values, indicating the absence of
diffusion-controlled accommodation mechanisms. The activation energy for GBS was determined to be $234\,\mathrm{kJ\,mol^{-1}}$, consistent with grain boundary
diffusion-assisted glide of grain boundary dislocations. These results demonstrate that the high strain-rate sensitivity commonly associated with GBS in polycrystals originates primarily from accommodation processes rather than the intrinsic sliding mechanism.
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Materials Science · Cross-listed from cond-mat.mes-hall
Disambiguating electrical detection of magnetization dynamics in magnetic insulators
Hanchen Wang, William Legrand, Shangyuan Wang et al. (+6 more)
Electrical detection of magnetization dynamics in
magnetic insulators underpins both fundamental studies of
magnon transport and the development of low-loss magnonic devices. In heavy-metal/
magnetic-
insulator heterostructures,
spin pumping and
spin-torque
ferromagnetic resonance (ST-FMR) are widely used for this purpose and are often treated separately in different measurement geometries. In practice, the competition between these two effects gives rise to electrical voltage signals of opposite signs, which can lead to ambiguous interpretations of the underlying physics. Here, we show how to disambiguate their respective contributions and provide a framework for interpreting experiments involving microwave excitation of
magnetic insulators and detection of magnetization dynamics via
spin-charge conversion in heavy metals. We systematically investigate
spin pumping and ST-FMR in nonlocal and local devices using Pt-capped thin films of thulium and bismuth-yttrium iron garnets. We show how
spin-wave character,
magnetic dissipation,
magnetic field orientation and device geometry govern the sign and magnitude of the resulting signals. In several cases, the voltage generated by microwave excitation changes sign between an out-of-plane or in-plane
magnetic configuration. We disentangle a contribution due to
spin pumping, induced by exponentially decaying propagating
spin waves, and a weakly distance-dependent contribution from ST-FMR, remotely induced by inductive coupling. We show that both the
spin wave excitation profile across the film thickness and
magnetic damping largely determine which of the two contributions dominates. Hence, the sign of the electrical signal cannot be uniquely assigned to the chirality of the
magnon modes.
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All authors Hanchen Wang, William Legrand, Shangyuan Wang, Davit Petrosyan, Hiroki Matsumoto, Alexander E. Kossak, Richard Schlitz, Ka Shen, Pietro Gambardella
Materials Science
Laser induced surface nitriding of niobium: phase evolution and superconducting behaviour
J. Frechilla, A. Frechilla, G.F. de la Fuente et al. (+3 more)
Laser nitriding represents a versatile approach for tailoring the surface properties of metals. Up to now, its effect on the superconducting response of niobium nitrides remains largely unexplored. In this work, the nitriding process of niobium by
laser irradiation under a controlled nitrogen atmosphere up to 2.50 bar, using a nanosecond pulsed
laser with wavelength of 1064 nm has been investigated. By independently tuning the nitrogen pressure, the two-dimensional accumulated fluence ($F_{2D}$) and the
laser irradiance, a
laser-processing map for the formation of either a combination of $\beta$-Nb$_2$N (hexagonal) and $\gamma$-Nb$_4$N$_{3\pm x}$ (tetragonal) phases or only the $\beta$-phase has been established. Systematic analysis by X-ray diffraction, scanning electron microscopy and electron backscatter diffraction revealed that the nitrogen-rich $\gamma$-phase forms in the near-surface layer through melting when $F_{2D}$ exceeds a certain value ($> 50 \,\mathrm{kJ/cm^2}$ at 2.50 bar). A $\beta$-layer is observed underneath, and further inside, there is a band of embedded $\beta$-grains in the Nb
matrix. Their size gradually decreases with increasing distance to surface, suggesting thermal gradients and a
diffusion formation mechanism. When the $\gamma$-phase becomes predominant, a significant increase in the superconducting critical temperature is observed, up to $T_c \approx 15\,\mathrm{K}$, and
magnetic irreversibility. For low $F_{2D}$ values ($\approx 7.5 \,\mathrm{kJ/cm^2}$ at 1.50-2.50 bar), the formation of a uniform nitride layer composed of sub-micron-sized $\beta$-Nb$_2$N grains results in a ca. fourfold enhancement in surface microhardness. These findings provide fundamental insights into
laser-induced nitriding of niobium to engineer mechanically robust and superconducting Nb-N layers.
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All authors J. Frechilla, A. Frechilla, G.F. de la Fuente, A. Larrea, L.A. Angurel, E. Martínez
Materials Science · Cross-listed from cond-mat.supr-con
Charge Density Wave Driven Topological Phase Transition in Vortices
Zhenhua Zhu, Ziqiang Wang and Dong E. Liu
The interplay between charge density waves (CDWs) and superconductivity is a central theme in
quantum materials, yet how CDW phase textures govern
vortex topology remains poorly understood. We develop a theoretical framework showing that the phase of a stripe CDW can switch a
magnetic vortex between topological and trivial regimes. Motivated by recent experiments, we propose two candidate mechanisms enabling phase-controlled switching of
vortex topology. In a direct-modulation scenario, the CDW acts as a periodic potential that locally renormalizes band parameters and can induce topological transitions, but it generally cannot reproduce the symmetric node/antinode trend without fine tuning. In contrast, in an inversion-
symmetry-breaking (ISB) scenario, a CDW node pinned to the
vortex center breaks local inversion and allows for the mixture of
spin-triplet pairing of Cooper pairs, producing a robust topological transition when this component dominates. Our results suggests CDW phase as a possible local handle to tune and test
vortex topology.
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Materials Science
Identification and Structural Characterization of Twisted Atomically Thin Bilayer Materials by Deep Learning
Haitao Yang, Ruiqi Hu, Heng Wu et al. (+11 more)
Two-dimensional materials are expected to play an important role in next-generation electronics and optoelectronic devices. Recently, twisted
bilayer graphene and transition metal dichalcogenides have attracted significant
attention due to their unique physical properties and potential applications. In this study we describe the use of optical microscopy to collect the color space of chemical vapor deposition (CVD) molybdenum disulfide ($\mbox{MoS}_2$), and the application of a semantic
segmentation convolutional neural network (CNN) to accurately and rapidly identify thicknesses of $\mbox{MoS}_2$ flakes. A second CNN model is trained to provide precise predictions on the twist angle of CVD-grown
bilayer flakes. This model harnessed a
dataset comprising over 10,000 synthetic images, encompassing geometries spanning from hexagonal to triangular shapes. Subsequent validation of the deep learning predictions on twist angles was executed through the second harmonic generation and Raman spectroscopy. Our results introduce a scalable methodology for automated inspection of twisted atomically thin CVD-grown
bilayer.
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All authors Haitao Yang, Ruiqi Hu, Heng Wu, Xiaolong He, Yan Zhou, Yizhe Xue, Kexin He, Wenshuai Hu, Haosen Chen, Mingming Gong, Xin Zhang, Ping-Heng Tan, Eduardo R Hernández, Yong Xie
Materials Science · Cross-listed from cond-mat.str-el
Yifan Wang, Chenchao Xu, Yi Liu et al. (+18 more)
Kagome metals are prone to charge-density wave (CDW),
magnetic, and superconducting phases, with their flat electronic band conducive for correlated physics. In contrast to the weakly correlated $A$V$_3$Sb$_5$ ($A$ = K, Rb, Cs) kagome metals with a $2\times2$ CDW, CsCr$_3$Sb$_5$ is a correlated metal with a flat band close to the
Fermi level, and exhibits a $4\times1$ CDW intertwined with
magnetic order. Under pressure, the intertwined orders are suppressed and give way to a dome of superconductivity that emerges from a non-
Fermi liquid normal state. Here, we solve the
crystal structure of the $4\times 1$ CDW state in CsCr$_3$Sb$_5$, and show it consists of Cr dimers separated by Cr chains. First-principles calculations show the dominant exchange interaction is
antiferromagnetic within the dimers, while the intra-chain and dimer-chain couplings are much weaker. The CDW transition of CsCr$_3$Sb$_5$ is found to be more strongly first-order than those in $A$V$_3$Sb$_5$, without significant soft
phonons or diffuse scattering above the CDW transition temperature. These findings suggest that fluctuating
antiferromagnetic dimers may play a major role in the electron pairing of superconducting CsCr$_3$Sb$_5$.
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All authors Yifan Wang, Chenchao Xu, Yi Liu, Jinke Bao, Jiayu Guo, Xiaoran Yang, Yuiga Nakamura, Hiroshi Fukui, Taishun Manjo, Daisuke Ishikawa, Alfred Q. R. Baron, Saizheng Cao, Rui Li, Zilong Li, Yanan Zhang, Ruihan Chen, Ming Shi, Huiqiu Yuan, Guanghan Cao, Chao Cao, Yu Song
Materials Science · Cross-listed from cond-mat.str-el
Ultrafast Current Switching from Quantum Geometry in Semimetals
Youngjae Kim, Sejoong Kim and Jun-Won Rhim
Technological progress towards next-generation electronics critically relies on achieving faster switching with reduced energy consumption. Because device operation speeds are fundamentally constrained by the intrinsic properties of constituent materials, identifying systems with inherently superior switching capabilities is essential. Here, we propose that semimetallic systems characterized by non-trivial
quantum geometry, including quadratic band-touching semimetals and singular flat bands, can serve as a promising platform for ultrafast switching at voltages compatible with modern electronics. We show that, in such
quantum geometric semimetals, an electric current is generated instantaneously upon application of a moderate external electric field, reaching its steady-state value. As a consequence, the current exhibits rapid and stable on-off switching behaviour under periodic optical pulse trains, demonstrating robustness under experimentally feasible conditions. In terms of switching speed, this
quantum geometric semimetal outperforms conventional metals,
semiconductors, and
graphene. We identify the microscopic origin of this behaviour as interband coupling governed by the
Hilbert-Schmidt
quantum distance, together with a finite density of states at the band-touching point. This mechanism further leads to a universal classification of conductivity for both gapless and gapped
quantum geometric semimetals. Finally, first-principles calculations suggest realistic material platforms, including
bilayer graphene, cyclic
graphene, monolayer bismuth and V3F8-in which the predicted instantaneous current switching can be directly realized, further supported by time-dependent density functional theory simulations performed for representative systems.
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Materials Science · Cross-listed from cond-mat.str-el
Experimental quantification of electronic symmetry breaking through orbital hybridization phase
Shungo Aoyagi, Shunsuke Kitou, Yuiga Nakamura et al. (+2 more)
Symmetry classification of
crystal structures has been central to predicting physical properties of materials. While such structural classification identifies which physical responses are
symmetry-allowed, the magnitudes of these responses are governed by the degree of
symmetry breaking in the electronic state. However, a well-defined quantitative descriptor for the electronic
symmetry breaking has been established only in limited cases such as electric polarization and magnetization. No analogous descriptor exists for most other types, including chirality. Here, we propose an experimental framework for quantifying electronic
symmetry breaking from the anisotropy of valence electron density distribution. We show that the orbital hybridization phases governing this anisotropy can be uniquely determined under site
symmetry constraints. Applying this framework to structurally
chiral transition-metal silicides, we determine hybridization phases from their valence electron densities observed by synchrotron X-ray diffraction. From the obtained complex hybridization, we quantify an electronic chirality $\chi$ and theoretically demonstrate that it is directly proportional to circular dichroism, establishing $\chi$ as a predictive descriptor of
chiral responses. This approach is systematically applicable to various point groups, offering a general route to quantifying electronic
symmetry breaking and predicting associated physical properties.
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All authors Shungo Aoyagi, Shunsuke Kitou, Yuiga Nakamura, Taka-hisa Arima, Naoya Kanazawa
Materials Science
Experimentally-validated multi-slice simulation of electron diffraction patterns
Xinke Xiao, Tianle Ma, Lingxuan Shao et al. (+4 more)
High-Resolution Electron Backscatter Diffraction (HR-EBSD) has advanced rapidly in recent years, significantly improving elastic strain measurements and dislocation density evaluation with submicron spatial resolution. To achieve better accuracy in the measurements, high-quality dynamical simulation patterns are required to be matched with experimental ones. Currently, the most widely used pattern simulation method, the Bloch Wave method (BW), can accurately predict the positions and brightness of Kikuchi poles and bands, but is intrinsically limited to perfect
crystal structures. Another simulation scheme, the multi-slice method (MS), follows the
evolution of electron waves as they travel through the sample. MS is advantageous in simulating various defect structures with more diffraction details. Yet, it is mainly considered for theoretical developments and has not been compared to experimental data. This paper optimizes the MS method by abandoning the high-energy hypothesis and utilizing higher-order Taylor expansions to approach the forward-only Schrodinger equation. Experimental EBSD patterns of polycrystal Al-Mg
alloys are used to challenge MS simulations as a reference for indexation. It is demonstrated that the 5th-order expansion of MS, referred to as MS5, achieves a good balance between computational cost and pattern precision. A tailored isotropic distortion correction model and standard stereographic triangle reconstruction enhance the precision of MS5 to be comparable with BW. To the best of our knowledge, this study provides the first comparison of MS EBSD simulations with experimental data. It opens new possibilities for EBSD characterization, such as reproducing diffraction patterns of
crystals with various defects.
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All authors Xinke Xiao, Tianle Ma, Lingxuan Shao, Jun Liu, Qiwei Shi, Canying Cai, Stéphane Roux