Materials Science
Gilbert Damping Parameters of Epitaxially-Stabilized Iron Gallium Thin Films from Ferromagnetic Resonance
Ruth Loh, Sujan Shrestha, Jiaxuan Wu et al. (+4 more)
Iron gallium (FeGa)
alloys are excellent rare-earth-free magnetostrictors. Through epitaxial stabilization, the disordered A2
alloy can be extended from 19% to 30% gallium resulting in a magnetostrictive coefficient almost twice than that which is seen in rare earth magnetostrictors like SmFe2. In a composite magnetoelectric structure, this makes epitaxially-stabilized iron gallium a key material for energy-efficient beyond CMOS technologies. The energy dissipation and speed of magnetoelectric switching, however, is affected by the
magnetic resonance frequency and damping. Here we report the
evolution of the
ferromagnetic resonance and key materials parameters (
magnetic anisotropy,
magnetic damping, and magnetostriction coefficient) for 70 nm thick epitaxially-stabilized single
crystal A2 FeGa films beyond 19% Ga. Using flip chip
ferromagnetic resonance (1-14 GHz), we find that the Gilbert damping parameter spans the range of 0.09-0.16 and decreases as the Ga concentration increases. This correlates an increasing magnetoelastic coupling with a reduction in the Gilbert damping. We find that the effective damping is a mix of contributions from the intrinsic
magnon-
phonon scattering and other scattering/dissipation mechanisms, with the latter being dominant especially at high Ga composition. Our results provide insight into the mechanism of
magnetic relaxation in metastable high magnetostriction materials and potential switching behavior of composite magnetoelectrics.
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All authors Ruth Loh, Sujan Shrestha, Jiaxuan Wu, Jia-Mian Hu, Christoph Adelmann, Florin Ciubotaru, John T. Heron
Materials Science
Binding Energies of Charged Particles on Dielectric Surfaces in Liquid Nitrogen
Ashok Timsina and Wolfgang Korsch
A new approach for determining the binding energies of charged particles, such as ions and electrons, on dielectric surfaces in cryogenic
liquids is introduced. The experimental technique outlined in this paper is employed to observe the buildup of charged particles on nonconductive surfaces using the electro-optic Kerr effect. The initial results of binding energy measurements on surfaces of deuterated tetraphenyl butadiene (dTPB)-coated and uncoated polymethyl methacrylate (PMMA) in
liquid nitrogen are presented. Under these conditions, the ions or electrons displayed binding energies of less than 1 meV. Although these findings were obtained in
liquid nitrogen, the methodology is not limited to cryogenic
liquids and is applicable to a wide variety of fluids, with no essential dependence on temperature.
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Materials Science · Cross-listed from cond-mat.mes-hall
Layer-engineered quantum anomalous Hall effect in twisted rhombohedral graphene
Zhangyuan Chen, Naitian Liu, Jiannan Hua et al. (+13 more)
Realizing programmable topological states in
quantum anomalous
Hall (QAH)
insulators requires the ability to design and dynamically tune their topological invariant, the Chern number C. Here, we report a designer QAH platform based on twisted rhombohedral
graphene family, in which C becomes a programmable and electrically tunable degree of freedom. By engineering the layer configuration in twisted monolayer-rhombohedral N-layer
graphene, denoted as (1+N)L, we realize QAH states with C=N at moire filling v=1, where the layer number N=3,4,5 directly sets the Chern number. Beyond such static layer programming, we demonstrate in-situ electrical control. In a twisted monolayer-trilayer device, the sign of C (chirality) can be switched by electrostatic doping or displacement field. Most strikingly, in twisted Bernal
bilayer-rhombohedral tetralayer
graphene denoted as (2+4)L, we drive a displacement-field-induced topological phase transition between two distinct QAH states with C=3 and C=4 in a single device. Our work establishes a layer-engineered and electrically tunable platform that transitions topological
quantum matter from discovery to design, opening the way toward on-demand engineering of correlated topological states and reconfigurable topological electronics.
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All authors Zhangyuan Chen, Naitian Liu, Jiannan Hua, Hanxiao Xiang, Wenqiang Zhou, Jing Ding, Xinjie Fang, Linfeng Wu, Le Zhang, Qianmei Chen, Xuanyu Chen, Kenji Watanabe, Takashi Taniguchi, Na Xin, Wei Zhu, Shuigang Xu
Materials Science · Cross-listed from cond-mat.mes-hall
Interlayer charge transfer from contact electrification in conducting micro and nanoscale thin film heterostructures
Sandeep Kumar and Ravindra G Bhardwaj
Contact electrification give rise to charge accumulation at the interface when two materials are brought into contact with each other. The charge accumulation at the interface will diffuse to the interior of the conducting material if the dimensions of the contacting conducting material is of the order of an unknown critical length scale. This contact electrification induced interlayer charge transfer will modify the fundamental physical properties of both the contacting materials. This review first discusses the reported experimental evidence of flexoelectricity induced contact electrification and interlayer charge transfer in conducting thin film based
heterostructures. The interlayer charge transfer creates a gradient of charge carrier in both the thin films constituting the
heterostructure and also modifies the electron-electron interactions. Further, the interlayer charge transfer changes the electron-
phonon coupling,
spin-
phonon coupling and magnetoelectronic coupling that give rise to new physical behavior, which did not exist prior to the interlayer charge transfer. The new physical behaviors from interlayer charge transfer and their mechanistic origins are reanalyzed and discussed, which include
spin-
Hall effect of charge carriers, topological
Hall effect of magnetoelectronic electromagnon, inhomogeneous magnetoelectronic multiferroic effect, flexoelectronic proximity effect and topological
spin texture. This review article presents a unified picture of current status and future directions that will provide the scientists a stepping stone for research in the field of flexoelectricity mediated contact electrification and interlayer charge transfer mediated behavior in the micro/nanoscale
heterostructures of the conducting materials.
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Materials Science
Correlated domain and crystallographic orientation mapping in uniaxial ferroelectric polycrystals by interferometric vector piezoresponse force microscopy
Ruben Dragland, Jan Schultheiß, Ivan N. Ushakov et al. (+2 more)
Ongoing advances in scanning probe microscopy techniques are continually expanding the possibilities for nanoscale characterization and correlated studies of functional materials. Here, we demonstrate how a recent extension of piezoresponse force microscopy (PFM), known as interferometric vector PFM, can be utilized for simultaneously mapping the local crystallographic orientations and the domain structure of distributed grains in uniaxial ferroelectric polycrystals. By shifting the
laser beam position on the cantilever, direction-dependent piezoresponse signals are acquired analogous to classical vector PFM, but without the need to rotate the sample. Using polycrystalline ErMnO$_{3}$ as a model system, we demonstrate that the reconstructed piezoresponse vectors correlate one-to-one with the crystallographic orientations of the micrometer-sized grains, carrying grain-orientation and domain-related information. We establish a versatile approach for rapid,
multimodal characterization of polycrystalline uniaxial ferroelectrics, enabling automated, high-throughput reconstruction of polarization and grain orientations with nanoscale precision.
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All authors Ruben Dragland, Jan Schultheiß, Ivan N. Ushakov, Roger Proksch, Dennis Meier
Materials Science
Grain-Growth Stagnation from Vacancy-Diffusion-Limited Disconnection Climb
Maik Punke, Abel H. G. Milor and Marco Salvalaglio
Grain growth in polycrystals typically stagnates at long times. We identify disconnection climb, limited by vacancy
diffusion, as a fundamental microscopic mechanism underlying this behavior. Using a phase-field
crystal framework extended to model vacancy
diffusion, we resolve grain-boundary migration on diffusive time scales and show that disconnection climb rates correlate with the characteristic grain size at which growth arrests. These results link vacancy transport, disconnection dynamics, and microstructural
evolution, establishing vacancy
diffusion as a key governing factor.
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Materials Science
Direct probing the quantum geometric tensor for bosonic collective excitations
Chi Wu, Takashi Oka, Shuichi Murakami et al. (+1 more)
The
quantum geometric tensor (QGT), whose real and imaginary parts define the
quantum metric and Berry
curvature, encodes the intrinsic geometry of
quantum states. While electronic QGT has recently become experimentally accessible and linked to diverse physical phenomena, its bosonic counterpart remains largely unexplored. Here we show that the dynamical structure factor encodes the momentum-space structure of bosonic wave functions and thereby provides direct access to the full bosonic QGT throughout the Brillouin zone. Applying this framework, we uncover clear
geometric signatures in the twofold quadrupole-Weyl
phonon of BaPtGe and the nodal-line
magnon in Gd, and further generalize the formalism to multiband systems. Our results establish a general route to measuring (non-)Abelian
quantum geometry in bosonic systems, a crucial step toward elucidating its impact on condensed matter phenomena.
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All authors Chi Wu, Takashi Oka, Shuichi Murakami, Tiantian Zhang
Materials Science
Dynamic Multiband Microscopy: A Universal Paradigm for Quantitative Nanoscale Metrology
Boris N. Slautin, Alwikh Rohi, Sanjay Mathur et al. (+4 more)
Scanning Probe Microscopy (SPM) is the primary tool for exploring nanoscale functionality, yet standard single-frequency operation is fundamentally limited, because the dynamic tip-sample interaction is mathematically underdetermined. While advanced methods such as Dual Amplitude Resonance Tracking (DART) and Band Excitation (BE) address this by tracking resonance, they face critical limitations: DART suffers from feedback instability on complex topographies, while Band Excitation is constrained by severe trade-offs between spectral resolution and acquisition speed. Here, we introduce Dynamic Multiband Microscopy (DMM), a general framework that bridges these gaps by combining multifrequency excitation with continuous frequency sweeping. We implement this within an automated experimental workflow that autonomously identifies and targets measurement points of interest. In combination with quantitative interferometric detection, this approach brings SPM to the fundamental limits of noise and spectral sensitivity. Validated on ferroelectric nanofibers, this platform enables simultaneous, crosstalk-free 3D polarization mapping, establishing a universal framework for autonomous, high-fidelity nanoscale metrology.
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All authors Boris N. Slautin, Alwikh Rohi, Sanjay Mathur, Arun Ichangi, Sergei V. Kalinin, Doru C. Lupascu, Vladimir V. Shvartsman
Materials Science
Determinants of Self-Interstitial Energetics in Refractory High-Entropy Alloys
Zichen Zhang, Zhiling Luo, Wang Gao et al. (+1 more)
Self-interstitials play a central role in governing the mechanical and anti-irradiation properties of refractory high-
entropy alloys (RHEAs), however, the prediction of interstitial formation energies (Ef) is formidable due to the chemically complex environments in RHEAs. Herein, we develop a framework based on the tight-binding model to quantify the effects of complex alloying and
lattice distortion on Ef. Our scheme reveals that Ef is jointly determined by the average d-band center of RHEAs and the d-band width of interstitial sites. Notably, the d-band width mainly depends on the interatomic hopping
matrix and atomic size-determined coordination number, which together make the metallic bonding around interstitials in RHEAs resemble the distance-dependence law of van der Waals forces. By capturing d-band coupling character, our descriptor describes both interstitial configurations within a universal framework. Our model reveals a new physical picture of interstitial formation, providing a useful tool for the design of high-performance RHEAs.
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All authors Zichen Zhang, Zhiling Luo, Wang Gao, Qing Jiang
Materials Science
Janus MoSSe/WSSe Heterobilayers as Selective Photocatalysts for Water Splitting
Mostafa Torkashvand, Saeedeh Sarabadani Tafreshi, Caterina Cocchi et al. (+1 more)
Identifying materials that simultaneously straddle the water redox potentials and possess an intrinsic electric field is crucial for achieving high
solar-to-hydrogen (STH) efficiency. Using state-of-the-art first-principles calculations, including a range-separated hybrid functional and
spin-orbit coupling, we investigate MoXY/WXY (X, Y = S, Se) Janus
bilayers for overall water splitting. We find a critical competition between the metal-to-metal chemical potential difference and the intrinsic dipoles at the interface between the Janus monolayers. We find that the Se-Se interfaced heterobilayer is intrinsically capable of driving water splitting, while its S-S counterpart can meet the redox requirements through pH modulation. For both configurations, a remarkable STH efficiency of 17.1% is anticipated. Furthermore, we predict a threshold of 1.0 eV for the built-in potential gradient to govern the transition from overall water splitting to band-edge pinning. Compared to homobilayers, heterobilayers benefit from the reciprocity between layer-specific dipoles and the Mo/W chemical potential difference, which promotes spatial separation and suppresses recombination, overall enhancing hydrogen production. Our results establish specific electronic descriptors for Janus
heterostructures, providing a rational design rule for maximizing
solar-driven hydrogen production in asymmetric two-dimensional materials.
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All authors Mostafa Torkashvand, Saeedeh Sarabadani Tafreshi, Caterina Cocchi, Surender Kumar
Materials Science · Cross-listed from physics.atm-clus
Interpretable, Physics-Informed Learning Reveals Sulfur Adsorption and Poisoning Mechanisms in 13-Atom Icosahedra Nanoclusters
Raiane Ferreira Monteiro, João Marcos T. Palheta, Tulio Gnoatto Grison et al. (+7 more)
Transition-metal nanoclusters exhibit structural and electronic properties that depend on their size, often making them superior to bulk materials for heterogeneous catalysis. However, their performance can be limited by sulfur poisoning. Here, we use dispersion-corrected density functional theory (DFT) and physics-informed machine learning to map how atomic sulfur adsorbs and causes poisoning on 13-atom icosahedral clusters from 30 different transition metals (3$d$ to 5$d$). We measure which sites sulfur prefers to adsorb to, the thermodynamics and energy breakdown, changes in structure, such as bond lengths and coordination, and electronic properties, such as $\varepsilon_d$, the HOMO-LUMO gap, and charge transfer. Vibrational analysis reveals true energy minima and provides ZPE-based descriptors that reflect the
lattice stiffening upon sulfur adsorption. For most metals, the metal-sulfur interaction mainly determines adsorption energy. At the same time, distortion penalties are usually moderate but can be significant for a few metals, suggesting these are more likely to restructure when sulfur is adsorbed. Using unsupervised k-means clustering, we identify periodic trends and group metals based on their adsorption responses. Supervised regression models with leave-one-feature-out analysis identify the descriptors that best predict adsorption for new samples. Our results highlight the isoelectronic triad \ce{Ti}, \ce{Zr}, and \ce{Hf} as a balanced group that combines strong sulfur binding with minimal structural change. Additional DFT calculations for \ce{SO2} adsorption reveal strong binding and a clear tendency toward dissociation on these clusters, linking electronic states,
lattice response, and poisoning strength. These findings offer data-driven guidelines for designing sulfur-tolerant nanocatalysts at the subnanometer scale.
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All authors Raiane Ferreira Monteiro, João Marcos T. Palheta, Tulio Gnoatto Grison, Octávio Rodrigues Filho, Renato Luis Tame Parreira, Diego Guedes-Sobrinho, Celso R. C. Rêgo, Alexandre C. Dias, Krys Elly de Araújo Batista, Maurício J. Piotrowski
Materials Science
Nanoparticle Self-assembly Assisted by Polymers: The Role of Shear Stress in the Nanoparticle Arrangement of Langmuir and Langmuir-Blodgett Films
Beatriz Martín-García and M. Mercedes Velázquez
We propose to use the self-assembly ability of a block copolymer combined with compression-expansion cycles to obtain CdSe
quantum dots (QDs) structures of different morphology. The methodology proposed consists in transferring onto mica mixed Langmuir monolayers of QDs and the
polymer poly (styrene-co-maleic anhydride) partial 2 buthoxy ethyl ester cumene terminated, PS-MA-BEE, previously sheared by 50 compression-expansion cycles. Results indicate that the shear stress takes out nanoparticles at the air-water interface from metastable states and promoted a new
equilibrium state of the Langmuir monolayer, then it was transferred onto mica by the Langmuir-Blodgett (LB) methodology and the morphology of the LB films was analyzed by Atomic Force Microscopy and Transmission Electron Microscopy measurements. Our results show that when the amplitude strain increases the QDs domain size decreases and the LB film becomes more ordered. The dynamic of the monolayer relaxation after cycling involves at least three timescales which are related to the damping of surface fluctuation, raft rearrangement and component movements inside each raft. Brewster Angle Microscopy allowed visualizing in situ the raft rearrangement at the air-water interface.
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Materials Science
Influence of Ru content on electrocatalytic activity and defect formation of Au-Pd-Pt-Ru compositionally complex solid solution thin films
Miran Joo, Huixin Xiu, Sabrina Baha et al. (+8 more)
Compositionally complex solid solutions (CCSSs) consist of a randomly mixed single phase with the potential to enhance electrocatalytic activity through their polyelemental surface atom arrangements. However, microstructural complexity originating from multiple principal elements influences local structure, chemistry, and
lattice strain, which might also affect electrocatalytic activity. Here, we investigate the effect of Ru content on electrochemistry and defect formation in Au-Pd-Pt-Ru CCSS thin films. Such defects could provide active sites when terminating at the CCSS surface or modify surface composition through preferential segregation. A thin-film material library covering a wide composition range was fabricated by room-temperature combinatorial co-sputtering. High-throughput compositional, structural and functional characterization, including electron microscopy equipped with energy dispersive X-ray spectroscopy, X-ray diffraction, and electrochemical screening, were used to correlate composition and microstructural features with catalytic activity. Three representative compositions selected from the library - Au68Pd13Pt15Ru4, Au27Pd24Pt23Ru26, and Au9Pd21Pt18Ru52 - were examined in detail. The three samples exhibit face-centered cubic structures, with
lattice contraction occurring with increasing Ru content. In addition, with increasing Ru content, a transition from a high density of nanotwins to high-density, atomic-layer stacking faults was observed. Moreover, the hydrogen
evolution reaction activity improves with higher Ru content. Atom probe
tomography reveals local compositional fluctuations, including element-specific enrichment and depletion at grain boundaries. The findings provide a new insight into surface atom arrangement design in the CCSS electrocatalysts with enhanced performance.
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All authors Miran Joo, Huixin Xiu, Sabrina Baha, Ridha Zerdoumi, Ningyan Cheng, Christoph Somsen, Yujiao Li, Aleksander Kostka, Wolfgang Schuhmann, Alfred Ludwig, Christina Scheu
Materials Science · Cross-listed from cond-mat.str-el
Large magneto-optical Kerr effect induced by collinear antiferromagnetic order
H. Yoshimochi, K. Yoshida, R. Oiwa et al. (+6 more)
In modern technology, the optical readout of
magnetic information is conventionally achieved by the magneto-optical Kerr effect, i.e., the polarization rotation of reflected light. The Kerr rotation is sensitive to time-reversal
symmetry breaking and generally proportional to magnetization, enabling optical readout of the up and down
spin states in ferromagnets. By contrast, antiferromagnets with a collinear antiparallel
spin arrangement have long been considered inactive to such magneto-optical responses, because of Tt-
symmetry (time-reversal T followed by translation t
symmetry) and lack of macroscopic magnetization. Here, we report the observation of
giant magneto-optical Kerr effect in a room-temperature
antiferromagnetic insulator alpha-Fe2O3. In this compound, the up-down and down-up
spin states induce the opposite sign of spontaneous Kerr effect, whose Kerr rotation angle turned out to be exceptionally large (~ 80 mdeg, comparable to typical ferromagnets). Our first-principles calculations successfully reproduce both the absolute magnitude and spectral shape of the Kerr rotation and ellipticity with remarkable accuracy, which unambiguously proves that it originates from a Tt-
symmetry-broken collinear
antiferromagnetic order, rather than magnetization. This compound hosts temperature-dependent transition between easy-plane and easy-axis
antiferromagnetic states, and their contrasting behaviors are also investigated in detail. The present results demonstrate that even a simple collinear
antiferromagnetic order can induce a
giant magneto-optical Kerr effect, and highlight Tt-
symmetry-broken antiferromagnets as a promising material platform for highly sensitive optical detection of up-down and down-up
spin states.
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All authors H. Yoshimochi, K. Yoshida, R. Oiwa, T. Nomoto, N. D. Khanh, A. Kitaori, R. Takagi, R. Arita, S. Seki
Materials Science
Near-atomic investigation on the elemental redistribution during co-precipitation of nano-sized kappa phase and B2 phase in an Al-alloyed lightweight steel
Bowen Zou, Yixu Wang, Xiao Shen et al. (+4 more)
In the present study, correlative transmission Kikuchi diffraction transmission electron microscopy (TKD-TEM) measurements, atom probe
tomography (APT), and density functional theory (DFT) calculations are used to reveal the elemental redistribution during co-precipitation of nanosized kappa and B2 phases in an FCC
matrix of an Al alloyed Fe-10Al-7Mn-6Ni-1C (wt.%) steel. Upon ageing at 800 C for 15 min, two co-nanoprecipitation modes are observed: B2 forming together with kappa and B2 forming separately from kappa in the FCC
matrix. APT reveals that the B2 precipitate next to kappa (referred to as B2I) is close to an FeAl type phase, while the isolated B2 precipitate (referred to as B2II) is close to a NiAl type phase. The kappa precipitates maintain a nearly constant Al content of approximately 18.4 at.% regardless of their precipitation position. DFT confirms that kappa may accommodate limited Ni substitution at Fe sites without losing structural stability, and that Fe Ni atomic exchange between kappa and B2 is thermodynamically favorable at 800 C. This exchange drives the B2 phase to evolve from a NiAl type towards an FeAl type, improving the stability of both phases during co-precipitation. These results provide understanding of kappa B2 interactions and offer insights for designing nanosized intermetallic strengthened microstructures in Al alloyed lightweight steels.
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All authors Bowen Zou, Yixu Wang, Xiao Shen, Philipp Krooss, Thomas Niendorf, Richard Dronskowski, Wenwen Song
Materials Science
Scaling Two-Dimensional Semiconductor Nanoribbons for High-Performance Electronics
Hao-Yu Lan, Shao-Heng Yang, Yongjae Cho et al. (+10 more)
As silicon transistors scale toward future technology nodes, three-dimensional architectures – including gate-all-around (GAA) nanoribbon and complementary field-effect transistors (CFETs) – require channel widths in the tens of nanometers to meet density targets. Monolayer transition metal dichalcogenides (TMDs), with their atomically thin bodies, are promising channel materials for these architectures, yet most TMD-based FETs remain limited to micrometer-scale widths. Here, we show that channel width scaling of monolayer MoS2 nanoribbon transistors not only preserves but also enhances device performance. Reducing the channel width from hundreds of nanometers to $\sim$30–40 nm increases the median on-current density by $\sim$42% and reduces the median subthreshold swing by $\sim$16%, with a champion device reaching 995 $\mu$A $\mu$m$^{-1}$ at a drain-to-source voltage of 1 V and an overdrive voltage of 2.5 V. We attribute these improvements to three mechanisms: minimal edge-induced disorder, enhanced gate electrostatics at ribbon edges, and more efficient side-contact injection, together reducing contact resistance from $\sim$860 $\Omega$ $\mu$m to $\sim$270 $\Omega$ $\mu$m. Extending the platform to n-type WS2 and p-type WSe2 FETs, we achieve WSe2 p-FET on-currents of 357 $\mu$A $\mu$m$^{-1}$. These findings suggest that monolayer TMD nanoribbon FETs are promising candidates for future ultra-scaled electronics.
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All authors Hao-Yu Lan, Shao-Heng Yang, Yongjae Cho, Yuanqiu Tan, Jun Cai, Zheng Sun, Chenyang Li, Lin-Yun Huang, Yi Wan, Lain-Jong Li, Thomas Beechem, Joerg Appenzeller, Zhihong Chen
Materials Science
GPUTB-2:An efficient E(3) network method for learning high-precision orthogonal Hamiltonian
Yunlong Wang, Zhixin Liang, Chi Ding et al. (+5 more)
Although equivariant neural networks have become a cornerstone for learning electronic
Hamiltonians, the intrinsic non-orthogonality of linear combinations of atomic orbitals (LCAO) basis sets poses a fundamental challenge. The computational cost of
Hamiltonian orthogonalization scales as O(N^3), which severely hinders electronic structure calculations for large-scale systems containing hundreds of thousands to millions of atoms. To address this issue, we develop GPUTB-2, a framework that learns implicitly orthogonality-preserving
Hamiltonians by training directly on electronic band structures. Benefiting from an E(3)-equivariant network accelerated by Gaunt tensor product and SO(2) tensor product layers, GPUTB-2 achieves significantly higher accuracy than GPUTB across multiple
benchmark systems. Moreover, GPUTB-2 accurately predicts large-scale electronic structures, including transport properties of temperature-perturbed SnSe and the band structures of magic-angle twisted
bilayer graphene. By further integrating this framework with the linear-scaling
quantum transport (LSQT) method, we investigate the electronic properties of million-atom amorphous
graphene and uncover pressure-induced electronic structure transitions in more complex amorphous silicon. Together, these results establish GPUTB-2 as a high-accuracy and scalable approach for predicting orthogonal
Hamiltonians.
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All authors Yunlong Wang, Zhixin Liang, Chi Ding, Junjie Wang, Zheyong Fan, Hui-Tian Wang, Dingyu Xing, Jian Sun
Materials Science · Cross-listed from cond-mat.str-el
When electrons meet ferroelastic domain walls in Strontium Titanate
Shashank Kumar Ojha, Jyotirmay Maity and Srimanta Middey
Strontium titanate (SrTiO$_3$), famously described by Nobel laureate K. A. Müller as the "drosophila of solid-state physics", has been extensively investigated over the last seventy five years for its intricate coupling of structural, electronic, and dielectric properties and continues to serve as a foundational platform for advancing
oxide electronics. In its pristine form, SrTiO$_3$ exhibits
quantum paraelectric behavior below 35 K and undergoes an antiferrodistortive phase transition near 105 K. This transition generates ferroelastic twin domains separated by a dense network of domain walls, which function as nanoscale structural defects with far-reaching consequences. While the static influence of ferroelastic domain walls on carrier transport in electron-doped SrTiO$_3$ is well established, recent experimental results show that the emergence of polarity at these walls, combined with strain fields and inherent
quantum fluctuations, induces correlated dynamical phenomena such as glass-like relaxations of electrons and
memory effects. In this review, we highlight these recent advances, focusing on the subtle interplay between the emergence of nanoscale polar order,
quantum fluctuations, and long-range strain fields. We propose that understanding charge carrier dynamics in the background of these complex ferroelastic domain wall landscapes offers a new paradigm for exploring electronic transport in the presence of local polar order and
quantum fluctuations, with broad implications for correlated
oxides.
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Materials Science · Cross-listed from cond-mat.mes-hall
Classical transport theory for the planar Hall effect with threefold symmetry
Akiyoshi Yamada and Yuki Fuseya
In recent years, the planar
Hall effect (PHE) has become a key probe of Berry
curvature and the anomalous
Hall effect (AHE). Threefold-symmetric signals under in-plane fields are often attributed to such
quantum mechanisms. Here, we establish a purely classical origin for a three-fold-symmetric PHE. The idea is simple yet decisive: a third-order expansion of the Boltzmann equation in the
magnetic field reveals that the threefold component originates from the relative positions of the mirror planes in the
crystals with respect to the measurement setups. Remarkably, the threefold contribution should be ubiquitous because this
symmetry condition can be realized across a broad range of
crystals. Numerical estimates based on concrete models further show that its amplitude is comparable to that expected from the AHE.
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Materials Science
Hybrid Epitaxial Al/InGaAs system: Solid-state dewetting and Al facet formation
A. Elbaroudy, N. Shaw, Sandra J. Gibson et al. (+4 more)
Hybrid
superconductor–
semiconductor platforms can host subgap electronic excitations such as Andreev bound states (ABSs); in topological regimes, a special zero-energy class, Majorana bound states (MBSs), can emerge. Here we report the growth of epitaxial Al films by molecular-beam epitaxy on $\mathrm{In_{0.75}Ga_{0.25}As}$ under near-room-temperature substrate conditions. Using a combination of AFM/SEM, cross-sectional TEM, and in situ RHEED, we map how substrate temperature and Al deposition rate govern film morphology, continuity, and interface quality. We identify a growth window that yields continuous, superconducting Al films with an abrupt $\mathrm{Al}/\mathrm{In_{0.75}Ga_{0.25}As}$ interface and no detectable indium interdiffusion. We further investigate the thermal stability of these films under in situ post-growth heating and ex situ annealing following surface oxidation. For unoxidized Al, rapid surface
diffusion triggers solid-state dewetting at approximately $165\,^\circ\mathrm{C}$, resulting in the formation of $\{111\}$-faceted Al islands. In contrast, the presence of a native
oxide largely suppresses dewetting, with failure occurring only locally at surface defects. Annealing above the indium melting point ($156.6\,^\circ\mathrm{C}$) induces significant In surface migration in both cases, leading either to localized interfacial In inclusions beneath Al agglomerates or to uniform surface contamination at sites of localized layer breakdown. Together, these results define growth and annealing conditions for thermally robust epitaxial Al on III–V
semiconductors and provide practical guidance for fabricating high-quality
superconductor–
semiconductor hybrid platforms for
quantum devices.
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All authors A. Elbaroudy, N. Shaw, Sandra J. Gibson, B. D. Moreno, F. Sfigakis, J. Baugh, Z. R. Wasilewski
Materials Science
Autonomous computational catalysis through an agentic research system
Honghao Chen, Jiangjie Qiu, Yi Shen Tew et al. (+1 more)
Autonomous
agents are beginning to transform scientific research from tool-assisted workflows toward self-sustaining discovery processes. Computational catalysis provides a representative challenge, as catalyst discovery requires high-level questions to be translated into coordinated model construction, atomistic simulation, mechanistic analysis, and iterative design across multiple scales. Here we introduce CatMaster, a catalysis-native agentic research system that recasts computational catalysis as a low-barrier virtual ecosystem for autonomous research. CatMaster maintains an evolving research state and extends capabilities through self-feedback across model construction, calculation, critique and catalyst-design decisions within one extensible environment. Across progressively challenging tasks, CatMaster converts natural-
language requests into concrete computational studies, from essential atomistic modelling and standard calculations to mechanism exploration and closed-loop catalyst design. It showed robust execution in representative computational-catalysis scenarios and near-leading performance across selected MatBench tasks, with
phonons scenario demonstrating its modelling self-
evolution capability. In the independent CO2-to-CO catalyst design case, CatMaster used iterative self-critique and evidence refinement to identify competitive B-CoN4 and NiN3B/N-NiN3B motifs. These results establish a virtual-ecosystem paradigm in which AI
agents move beyond simulation execution toward end-to-end computational research, providing a foundation for autonomous discovery in catalysis and materials science.
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All authors Honghao Chen, Jiangjie Qiu, Yi Shen Tew, Xiaonan Wang
Materials Science
Current-driven nonlinear skyrmion dynamics in altermagnets
Yang Liu, Zhejunyu Jin, Jie Liu et al. (+1 more)
The center of mass and helicity are two dynamic degrees of freedom of skyrmions. In this work, we study the current-driven skyrmion motion in frustrated altermagnets. Contrary to conventional wisdom, we find that the skyrmion helicity is not locked with the skyrmion
Hall angle, but unidirectionally rotates with a global angular velocity proportional to the square of the current density. In addition, we find that the helicity rotation velocity is highly anisotropic, depending on the direction of current flows. We also observe helicity oscillation in the terahertz regimes, where the nonlinear mixing between the fast and slow modes generates a
magnon frequency comb. Full atomistic
spin dynamics simulations verify our theoretical predictions. Our results establish frustrated altermagnets as a promising platform for skyrmionics, THz technology, and frequency comb.
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All authors Yang Liu, Zhejunyu Jin, Jie Liu, Peng Yan