Materials Science · Cross-listed from cond-mat.str-el
Cavity-induced coherent magnetization and polaritons in altermagnets
Mohsen Yarmohammadi, Libor Šmejkal and James K. Freericks
Altermagnets feature antiparallel
spin sublattices with $d$-, $g$-, or $i$-wave
spin order, yielding nonrelativistic
spin splitting without net magnetization. We show that
embedding a two-dimensional $d$-wave altermagnet in a driven optical cavity induces a finite, tunable magnetization. Coherent
photon driving couples selectively to electronic sublattices, and the resulting altermagnets'
symmetry-broken
spin texture yields a pronounced steady-state
spin imbalance – coherent magnetization – absent in conventional antiferromagnets for the same
lattice configuration. A mean-field Lindblad analysis reveals the dominance of quadratic over linear couplings. In the strong-coupling regime, distinct polariton signatures emerge in the steady state of induced magnetization. This work demonstrates cavity control of altermagnets for spintronic applications.
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Materials Science
Coherent and Dynamic Small Polaron Delocalization in CuFeO$_{2}$
Jocelyn L. Mendes, Srijan Bhattacharyya, Chengye Huang et al. (+10 more)
Small polarons remain a significant bottleneck in the realization of efficient devices using transition metal
oxides. Routes to engineer small polaron coupling to electronic states and
lattice modes to control carrier localization remain unclear. Here, we measure the formation of small polarons in CuFeO$_{2}$ using transient extreme ultraviolet reflection spectroscopy and compare it to theoretical predictions in realistically parameterized Holstein models, demonstrating that polaron localization depends on its coupling to the high-frequency versus low-frequency components of the
phonon bath. We measure that small polaron formation occurs on a comparable ~100 fs timescale to other Fe(III) compounds. After formation, a dynamic delocalization of the small polaron occurs through a coherent
lattice expansion between Fe-O layers and charge-sharing with surrounding Fe(IV) states. Our simulations of polaron formation dynamics reveal that two major factors dictate polaron formation timescales:
phonon density and reorganization energy distributions between acoustic and optical modes, matching experimental findings. Our work provides a detailed, real-time observation of how electronic-structural coupling in a polaron-host material can be leveraged to suppress polaronic effects for various applications.
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All authors Jocelyn L. Mendes, Srijan Bhattacharyya, Chengye Huang, Jonathan M. Michelsen, Isabel M. Klein, Finn Babbe, Thomas Sayer, Tianchu Li, Jason K. Cooper, Hanzhe Liu, Naomi S. Ginsberg, Andrés Montoya-Castillo, Scott K. Cushing
Materials Science
Exceptional Antimodes in Multi-Drive Cavity Magnonics
Mawgan A. Smith, Ryan D. McKenzie, Alban Joseph et al. (+2 more)
Driven-dissipative systems provide a natural setting for the emergence of exceptional points – i.e. non-Hermitian degeneracies where eigenmodes coalesce. These points are important for applications such as sensing, where enhanced sensitivity is required, and exhibit interesting and useful phenomena that can be controlled with experimentally accessible parameters. In this regard a four-port, three-mode, cavity-magnonics platform is demonstrated in which two microwave excitations can be precisely phase shifted and/or attenuated relative to one another. Destructive interference between the hybridised cavity-
magnon modes is shown to give rise to antimodes (antiresonances) in the transmission spectrum, enabling coherent perfect extinction of the outgoing signals at selected ports. This interference can be used to actively tune the position and properties of exceptional points, without the fine tuning conventionally required to obtain exceptional points. Such controllable, interference-based engineering of exceptional points provides a practical and flexible pathway toward next-generation, high-sensitivity sensing devices operating at microwave frequencies.
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All authors Mawgan A. Smith, Ryan D. McKenzie, Alban Joseph, Robert L. Stamps, Rair Macêdo
Materials Science · Cross-listed from cond-mat.str-el
Finite temperature magnetic interactions from first principles
Ravi Kaushik, Ryota Ono and Sergey Artyukhin
Density functional theory has demonstrated remarkable predictive power in calculating
magnetic properties at zero temperature. At finite temperatures, thermally excited
phonons may affect magnetism. Efficient ab-initio methods to calculate the temperature dependence of
magnetic exchange interactions are still lacking despite the importance of room temperature magnetism for applications. Exchange is controlled by an interplay between metal-ligand hybridization, Hubbard repulsion, band gap, interatomic distances and bond angles, all of which change with temperature. Here we present a method to calculate the exchange interactions at finite temperatures from first principles using only two supercell calculations and quantify these mechanisms. Changes in bond angles and the band gap are identified as a primary factors. In NiO with 180-degree bonds exchange decreases with temperature, while in Cr$_2$O$_3$ with the bond angles away from 180 degrees the exchange increases by 10% at room temperature.
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Materials Science
Confinement-Induced One-Dimensional Magnetism in CrSBr Chains via Carbon Nanotube Encapsulation
Diego López-Alcalá, Alberto M. Ruiz, Andrei Shumilin et al. (+1 more)
Encapsulating low-dimensional
magnetic materials within carbon nanotubes (CNTs) offers a compelling route to stabilize unconventional
magnetic states and engineer
quantum functionalities at the limit of miniaturization. In this work, we systematically investigate the structural, electronic, and
magnetic properties of one-dimensional (1D) CrSBr chains encapsulated within CNTs using density functional theory (DFT) and
spin dynamics simulations. We demonstrate the structural stability of CrSBr@CNT, where confinement and charge transfer cooperate to stabilize ferromagnetism in the 1D limit, which persists up to 50 K. These findings position CrSBr@CNT as a model platform for realizing 1D magnetism and establish CNT encapsulation as a powerful strategy for exploring emergent
quantum spin phenomena and engineering nanoscale spintronic devices.
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All authors Diego López-Alcalá, Alberto M. Ruiz, Andrei Shumilin, José J. Baldoví
Materials Science
Engineering phase-frustration induced flat bands in an aza-triangulene covalent Kagome lattice
Yuyi Yan, Fujia Liu, Weichen Tang et al. (+4 more)
Pi-conjugated covalent organic frameworks (COFs) provide a versatile platform for the realization of designer
quantum nanomaterials. Strong electron-electron correlation within these artificial
lattices can give rise to exotic phases of matter. Their experimental realization however requires precise control over orbital
symmetry, charge localization, and band dispersion all arising from the effective hybridization between molecular linkers and nodes. Here, we present a modular strategy for constructing diatomic Kagome
lattices from aza-[3]triangulene (A[3]T) nodes, in which a D3h symmetric ground state is stabilized through resonance contributions from a cumulenenic linker. First-principles density-functional theory and scanning tunnelling spectroscopy reveal that the hybridization of a sixfold degenerate set of edge-localized Wannier functions in the unit
cell gives rise to orbital-phase frustration-induced non-trivial flat bands. These results establish a general design principle for engineering orbital interactions in organic
lattices and open a pathway toward programmable COF-based
quantum materials with correlated electronic ground states.
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All authors Yuyi Yan, Fujia Liu, Weichen Tang, Han Xuan Wong, Boyu Qie, Steven G. Louie, Felix R. Fischer
Materials Science
Multiscale Modeling of Abnormal Grain Growth: Role of Solute Segregation and Grain Boundary Character
Albert Linda, Rajdip Mukherjee and Somnath Bhowmick
Abnormal grain growth (AGG) influences the properties of polycrystalline materials; however, the underlying mechanisms, particularly the role of solute segregation at the grain boundary (GB), are difficult to quantify precisely. This study demonstrates a multiscale framework that integrates atomic-scale segregation energetics (using density functional theory) with mesoscale grain growth dynamics (using phase-field model) to investigate AGG, using $\alpha$-Fe as an example system. Multisite segregation energies are calculated for symmetric tilt grain boundaries (STGBs) along the $\langle 110 \rangle$ axis for nine different solutes (Co, Cr, Mn, Mo, Nb, Ni, Ti, W, and V), encompassing three different types of coincident site
lattice (CSL) boundaries: $\sum 3 (11\bar{2})$, $\sum 9 (\bar{2}21)$, and $\sum 3 (\bar{1}11)$. The model takes into account the effect of solute drag on GB mobility, estimated using a bulk solute concentration of 0.1 at%. The results demonstrate that AGG originates due to GB anisotropy, the extent of which largely depends on the type of solute atom present. Such a complex dependence necessitates using a multiscale model to understand AGG comprehensively. In general, low-energy $\Sigma 3$ boundaries are found to have higher mobility and show preferential growth for most of the solutes, other than Co. The study reveals how the distribution of GB types significantly influences AGG. When 10-30% of the GBs are high-mobility type, crown-like morphologies are observed, leading to AGG. These findings underscore the critical role of GB chemistry and crystallography in governing AGG, and the model can be generalized to provide a predictive framework for controlling grain growth through strategic solute design in advanced
alloys.
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Materials Science · Cross-listed from quant-ph
Shin-Ming Huang
Geometry and
topology are fundamental to modern condensed matter physics, but their precise connection in
quantum systems remains incompletely understood. Here, we develop an analytical scheme for calculating the
curvature of the
quantum metric of Bloch bands. Using a gauge-invariant formulation based on eigenprojectors, we construct the full Riemannian geometry of the
quantum-state
manifold and apply it to a two-dimensional two-band model. We find that the Gauss
curvature is constant over regular regions, but the
manifold inevitably develops a closed curve of singular points where the metric tensor degenerates. These singularities obstruct the conventional Gauss-Bonnet
theorem. By introducing the notion of a front and a signed area form, we derive a generalized Gauss-Bonnet relation that includes a singular
curvature term defined along the fold curve. This result establishes a direct, quantized link between the total signed Gauss
curvature and the Chern number, providing a unified
geometric interpretation of Berry
curvature and
quantum metric. This framework bridges differential geometry and topological band theory, revealing how singular folds mediate the discrepancy between
quantum volume and topological charge.
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Materials Science
Lattice excitations with finite polarization and magnetization
Mike Pols, Carl P. Romao and Dominik M. Juraschek
Ferrons are a type of quasiparticle corresponding to elementary excitations of the ferroelectric order. Analogously to how
magnons modulate and transport magnetization, ferrons modulate and transport electric polarization. Here, we introduce multiferrons as elementary excitations with both electric and
magnetic character. Multiferrons lead to a tilt and elliptical precession of the polarization and at the same time create a magnetization through the mechanism of dynamical multiferroicity. Using first-principles calculations for LiNbO$_3$, we show that the electric polarization of multiferrons is perpendicular to the
equilibrium ferroelectric polarization, whereas the magnetization is parallel to it. Our calculations further demonstrate that multiferrons carry net electric and
magnetic quadrupole and octupole moments, which we term multipolons. These multipolons could couple to internal multipolar degrees of freedom, for example in altermagnets, or to external probes such as
neutrons, leading to potentially experimentally observable phenomena following coherent or thermal excitation of multiferrons.
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Materials Science
Atomically-resolved exciton emission from single defects in MoS$_2$
Lysander Huberich, Eve Ammerman, Gu Yu et al. (+11 more)
Understanding how atomic defects shape the nanoscale optical properties of two-dimensional (2D)
semiconductors is essential for advancing
quantum technologies and optoelectronics. Using scanning tunneling spectroscopy (STS) and luminescence (STML), we correlate the atomic structure and optical fingerprints of individual defects in monolayer MoS$_2$. A
bilayer of hexagonal boron nitride (hBN) effectively decouples MoS$_2$ from the
graphene substrate, increasing its band gap and extending the defect charge state lifetime. This enables the observation of sharp STML emission lines from MoS$_2$
excitons and trions exhibiting nanoscale sensitivity to local potential fluctuations. We identify the optical signatures of common point defects in MoS$_2$: sulfur vacancies (Vac$_\text{S}^-$), oxygen substitutions (O$_\text{S}$), and negatively charged carbon-hydrogen complexes (CH$_\text{S}^-$). While Vac$_\text{S}^-$ and O$_\text{S}$ only suppress pristine excitonic emission, CH$_\text{S}^-$ generate defect-bound
exciton complexes ($A^-X$) about 200\,meV below the MoS$_2$
exciton. Sub-nanometer-resolved STML maps reveal large spectral shifts near charged defects, concurrent with the local band bending expected for band-to-defect optical transitions. These results establish an atomically precise correlation between structure, electronic states, and optical response, enabling deterministic engineering of
quantum emitters in 2D materials.
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All authors Lysander Huberich, Eve Ammerman, Gu Yu, Yining Ren, Sotirios Papadopoulos, Chengye Dong, Joshua A. Robinson, Kenji Watanabe, Takashi Taniguchi, Oliver Gröning, Lukas Novotny, Tingxin Li, Shiyong Wang, Bruno Schuler
Materials Science
Atomic cluster expansion potential for the Si-H system
Louise A. M. Rosset and Volker L. Deringer
The silicon-hydrogen system is of key interest for
solar-
cell devices, including both crystalline and amorphous modifications. Elemental amorphous Si is now well understood, but the atomic-scale effects of hydrogenating the silicon
matrix remain to be fully explored. Here, we present a machine-learned interatomic potential model based on the atomic cluster expansion (ACE) framework that can describe a wide range of Si-H phases, from crystalline and amorphous bulk structures to surfaces and molecules. We perform numerical and physical validation across a range of hydrogen concentrations and compare our results to experimental findings. Our work constitutes an advancement toward the exploration of large structural models of a-Si:H at realistic device scales.
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Materials Science
Specimen preparation for atom probe tomography analysis of complex multifunctional nanoparticles and nanostructures: state-of-the-art and challenges
Varatharaja Nallathambi, Se-Ho Kim, Nikita Polin et al. (+4 more)
Atom probe
tomography (APT) provides the three-dimensional composition of materials at near-atomic length scales, achieving detection limits in the range of tens of atomic parts-per-million regardless of element type. APT requires the specimen to be shaped as a needle with a tip radius of ~100 nm. The development of site-specific lift-out procedures using focused ion beam-scanning electron microscopy (FIB-SEM) has enabled APT analysis of multifunctional materials, advancing our understanding of their structure-composition-property relationships. Yet these approaches are not readily suitable for analyzing many nanomaterials. Co-electrodeposition of metallic films forms a composite containing the nanomaterials of interest, thereby facilitating APT specimen preparation and enabling analysis of nanowires, nanosheets, and nano- and microparticles, etc. In this perspective article, we showcase diverse examples from simple elementary to compositionally complex
alloys of varying dimensionalities, from individual nanoparticles to aerogel structures. We emphasize the challenges encountered with specific material classes during co-electrodeposition procedures and provide recommendations for improving specimen preparation protocols to enhance measurement yield, thereby advancing APT analysis capabilities for optimizing the performance of functional nanomaterials.
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All authors Varatharaja Nallathambi, Se-Ho Kim, Nikita Polin, Natalia F. Shkodich, Sven Reichenberger, Stephan Barcikowski, Baptiste Gault
Materials Science
Transitions between positive and negative charge states of dangling bonds on a halogenated Si(100) surface
T. V. Pavlova and V. M. Shevlyuga
Dangling bonds (DBs) are common defects in silicon that affect its electronic performance by trapping carriers at the in-gap levels. For probing the electrical properties of individual DBs, a scanning tunneling microscope (STM) is an effective instrument. Here we study transitions between charge states of a single DB on chlorinated and brominated Si(100)-2$\times$1 surfaces in an STM. We observed transitions between positively and negatively charged states of the DB, without the participation of the neutral state. We demonstrated that the $(+/-)$ transition occurs when the DB and substrate states are out of
equilibrium. This transition is related to the charge neutrality level (CNL), which indicates a change in the DB's character from donor-like to acceptor-like. The STM voltage at which the $(+/-)$ transition took place varied depending to the electrostatic environment of the DB. Our results complement the understanding of the electronic properties of the DBs, and they should be taken into account in applications that use charge manipulation on the DBs.
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Materials Science
Calculations of pathways of precise P incorporation into chlorinated Si(100) surface
T. V. Pavlova
The precise incorporation of a phosphorus atom into a silicon surface is essential for the fabrication of nanoelectronic devices in which the active area is formed from single
impurities. The most accurate approach employs scanning tunneling microscopy (STM) lithography, which may be done with atomic precision. However, the accuracy decreases when phosphorus is incorporated into the surface because P substitutes one of two neighboring Si atoms with equal probability. Here, the P-Si exchange mechanism was studied theoretically on a chlorinated Si(100) surface with an asymmetric configuration of Cl vacancies surrounding the P atom. Density functional theory was used to estimate the activation barriers and exchange rates between a P atom and neighboring Si atoms on a Si(100)-2$\times$1-Cl surface with three Cl vacancies. The calculation of various P-Si exchange pathways revealed that phosphorus has a higher probability of substituting one Si atom than the others due to the asymmetric configuration of Cl vacancies. Based on the theoretical study of the P-Si exchange mechanism and experimental results from previous works, a scheme for controlled P incorporation into the silicon surface without uncertainty is proposed.
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Materials Science
Surface diffusion of phosphorus on Si(100) after PBr3 adsorption
T. V. Pavlova and V. M. Shevlyuga
Phosphorus
diffusion on a Si(100) surface was studied using scanning tunneling microscopy (STM) at temperatures of 77 and 300 K. The phosphorus source utilized was the PBr$_3$ molecule, which fully dissociates on the surface at 77 K. We observed
diffusion of P atoms both along and across the rows of Si dimers. To support the observation of different
diffusion pathways of phosphorus, activation energy calculations were performed using density functional theory. At 77 K, phosphorus
diffusion started and (or) finished mostly in bridge positions. At 300 K, phosphorus diffuses predominantly between end-bridge positions, accompanied by bromine
diffusion. The presence of Br near phosphorus significantly restricts its mobility. Additionally, phosphorus was found to diffuse to an oxygen atom that appeared on the surface as a result of water adsorption. This
diffusion occurs because the P site near the oxidized dimer is more stable compared to that on the clean surface. The obtained results complement the knowledge about the interaction of phosphorus with the silicon surface, specifically the phosphorus
diffusion pathways on the Si(100) surface.
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Materials Science
Quantifying non-Gaussian diffusion in transient microscopy using excess kurtosis
Enrique Arévalo Rodríguez, Marc Meléndez Schofield, Jorge Cuadra et al. (+1 more)
Research on energy transport has advanced in recent years with the emergence of transient microscopy techniques that allow for imaging of carriers with high spatial and temporal resolution. In this context, transient scattering microscopy (TScM), has emerged as an alternative to traditional techniques. However, the sensitivity of TScM to different carriers can complicate the interpretation of results, highlighting the need to develop models tailored to TScM. Here, TScM is used to visualize
exciton transport in bulk TMDCs. We show that
exciton populations exhibit non-Gaussian profiles by analyzing the their excess kurtosis. Numerical simulations incorporating anomalous
diffusion – such as Auger recombination and trap states – reproduce these experimental observations. Furthermore, by tuning the injected carrier density, we demonstrate that the temporal signature of the kurtosis is distinct for Auger-dominated and trap-dominated regimes. Additionally, we find that traditional Gaussian-fitting methods can yield inconsistent results for the extracted diffusivities. As an alternative, we implement a discrete variable calculation which yields robust, consistent diffusivity values. Our results establish kurtosis as a vital diagnostic parameter for identifying anomolous
diffusion and demonstrate the necessity of moving beyond Gaussian approximations for accurate analysis of TScM data.
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All authors Enrique Arévalo Rodríguez, Marc Meléndez Schofield, Jorge Cuadra, Ferry Prins
Materials Science
A finite-element Delta-Sternheimer approach for computing accurate all-electron RPA correlation energies of polyatomic molecules
Hao Peng, Haochen Liu, Chuhao Li et al. (+2 more)
Attaining a reliable complete basis set (CBS) limit remains a significant challenge in ab initio correlated electronic-structure calculations. Building on our previous work for atoms and diatomic molecules, we present a finite-element (FE) Delta Sternheimer approach for numerically accurate random phase approximation (RPA) calculations applicable to general molecules. This approach seamlessly integrates atomic orbital basis sets with FE grids, enabling an arbitrary precision representation of first order wavefunctions. As a result, the density response function and RPA correlation energies can be computed with fully controlled numerical precision. The Delta Sternheimer approach thus provides direct access to RPA correlation energies at the CBS limit, eliminating reliance on conventional extrapolation schemes. We apply this approach to two problems: The energy hierarchy of 20 water-dimer configurations and the atomization energies of 50 molecules from the G2 set. For the water dimer, we examine the basis set dependence of the isomer energy ordering. For the G2 set, we investigate the residual numerical uncertainty in the conventional extrapolated CBS limit, both with and without correction for basis-set superposition error (BSSE).
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All authors Hao Peng, Haochen Liu, Chuhao Li, Hehu Xie, Xinguo Ren
Materials Science
Facet Specific Electron Conduction in Pentavalent (W5+) WO3 Drives Superior Photocatalytic CO 2 Reduction in (002) Plane
Muhammad Rizwan Kamal, Mohammad Z. Rahman, Amil Aligayev et al. (+17 more)
This article reports a concept of heat-induced topological modifications of non-layered WO 3 followed by successful synthesis of oxygen-vacant more-porous nanosheets with exposed active (002) facet. Experimental measurements and Density Functional Theory (DFT) calculations have revealed that the photoexcited electrons are found to accumulate preferentially on (002) facet to yield enhanced electron conduction, and consequently, strengthen the reduction potential as active catalytic sites for photocatalytic CO2 reduction. Owing to these beneficial properties, the more-porous nanosheets of WO 3 with (002) facet have exhibited superior performance than that of less-porous nanosheets of WO3 with (220) facet and bulk WO3 with (205) facet. This study therefore provides a new understanding of regulating physical, optical, and electronic properties through intricate atomic structure modulation of WO3, and may find widespread application in optoelectronics, sensors, and energy conversion.
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All authors Muhammad Rizwan Kamal, Mohammad Z. Rahman, Amil Aligayev, Min Liu, Li Zhong, Pengfei Xia, Yueheng Li, Yue Ruan, Xia Xiang, Pir Muhammad Ismail, Qaisar Alam, Ahmed Ismail, Muhammad Zahid, Xiaoqiang Wu, Abdullah N. Alodhayb, Qing Huang, Raj Wali Khan, Fazal Raziq, Sharafat Ali, Liang Qiao
Materials Science
CoNi-MOF laccase-like nanozymes prepared by dielectric barrier discharge plasma for treatment of antibiotic pollution
Chao Liu, Yi Cao, Qi Xia et al. (+2 more)
Laccase is a natural green catalyst and utilized in pollution treatment. Nevertheless, its practical application is constrained by limitations including high cost, poor stability, and difficulties in recovery. Herein, with inspiration from catalytic mechanism of natural laccase, we designed and prepared a bimetallic metal-organic framework, namely, CoNi-MOF, using low-temperature
plasma (LTP) technology. We employed dielectric barrier discharge (DBD)
plasma to prepare CoNi-MOF, and by precisely modulating the N2/O2 gas ratio, we could modulate the distribution concentration of oxygen vacancies in CoNi-MOF. Experimental investigations and density functional theory (DFT) calculations elucidated that the critical role of the oxygen vacancies in enhancing the laccase-like activity, which promoted the activation of molecular oxygen (O2) for generation of reactive oxygen species (ROS). Compared to natural laccase, CoNi-MOF exhibited superior catalytic performance in the degradation of antibiotic tetracycline (TC), along with enhanced resistance to harsh environmental conditions, improved stability, and low biotoxicity. Notably, aeration increased the dissolved oxygen (DO) content, further improving the TC degradation efficiency. As such, this study not only proposes a facile and efficient low-temperature
plasma technology for synthesizing high-performance laccase-like nanozymes but also provides a promising and environmentally friendly strategy for the remediation of antibiotic contamination in the environment.
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All authors Chao Liu, Yi Cao, Qi Xia, Amil Aligayev, Qing Huang
Materials Science
Synergistic modulation of band structure and phonon transport for higher thermoelectric performance of WSe2
Mazhar Hussain Danish, Amil Aligayev, Zahir Muhammad et al. (+8 more)
Tungsten diselenide (WSe2) emerges as a promising thermoelectric (TE) candidate due to its high thermopower (S), cost-effectiveness, and environmentally friendly characteristics. However, pristine WSe2 exhibits limited electrical conductivity (sigma), a low power factor (PF), and high
lattice thermal conductivity (k_L), which restrict its overall TE performance. Here, we show that through co-doping of Nb for W and Te for Se in WSe2, its power factor increases 17-fold, reaching 8.91 microW cm^-1 K^-2 at 850 K. Simultaneously, its
lattice thermal conductivity (k_L) decreases from 1.70 W m^-1 K^-1 to 0.48 W m^-1 K^-1. Experiments and density functional theory (DFT) analysis demonstrate that the enhancement of PF is linked to an increased density of states, higher effective mass (md*), improved mobility (mu), and elevated electrical conductivity (sigma) owing to the replacement of Se2- with Te2-; while the observed 72% reduction in k_L results primarily from
phonon scattering at Te-Se and Nb-W defects. As a result, a remarkable ZT_max ~ 1 is obtained at 850 K for the sample W0.95Nb0.05Se2-yTey with y = 0.3, which is about a 30-fold increase compared to WSe2, proving that Nb and Te co-doping in WSe2 can significantly boost its TE performance.
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All authors Mazhar Hussain Danish, Amil Aligayev, Zahir Muhammad, Tao Chen, Adil Mansoor, Zia Ur Rahman, F. J. Dominguez-Gutierrez, Di Li, Jian Zhang, Zhuang Hao Zheng, Xiaoying Qin
Materials Science · Cross-listed from cond-mat.mes-hall
Gate-tunable Josephson diodes in magic-angle twisted bilayer graphene
A. Rothstein, R. J. Dolleman, L. Klebl et al. (+8 more)
We report low-temperature measurements of two adjacent, gate-defined Josephson junctions (JJs) in magic-angle twisted
bilayer graphene (MATBG) at a moiré filling factor near $\nu = -2$. We show that both junctions exhibit a prominent, gate-tunable Josephson diode effect, which we explain by a combination of large kinetic inductance and non-uniform supercurrent distribution. Despite their proximity, the JJs display differences in their interference patterns and different diode behavior, underscoring that microscopic inhomogeneities such as twist angle variations shape the non-uniform supercurrent and drive the diode behavior. As a result, the nonreciprocal supercurrent can be tuned by gate voltage, enabling tuning of the diode efficiency and even reversing the polarity at fixed
magnetic fields. Our findings offer potential routes for tailoring Josephson diode performance in superconducting
quantum circuits.
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All authors A. Rothstein, R. J. Dolleman, L. Klebl, A. Achtermann, F. Volmer, K. Watanabe, T. Taniguchi, F. Hassler, L. Banszerus, B. Beschoten, C. Stampfer
Materials Science
Antiphase boundaries in Ni-Mn-Ga single crystal - experiment and model
O. Heczko, F. Maca, V. Drchal et al. (+3 more)
Thermally induced antiphase boundaries (APBs) in
ferromagnetic, ordered Ni-Mn-Ga single
crystal exhibit complex, irregular shapes and closed loops without any
lattice plane preferences. The APBs were visualized on polished (100) surface using
magnetic force microscopy (MFM) at the same location in parent cubic austenite and monoclinic martensite with uniaxial
magnetic anisotropy. Based on ab-initio calculation we suggest that one APB curve with dark and light contrast consists of a pair of APB interfaces with narrow, only one-layer thick, core with structural partial B2' order in contrast to full L21 order of bulk. Calculated
magnetic contrast using magnetostatic continuum simulations agrees well with MFM observation.
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All authors O. Heczko, F. Maca, V. Drchal, L. Fekete, L. Straka, J. Zemen
Materials Science
Unravelling the Catalytic Activity of Dual-Metal Doped N6-Graphene for Sulfur Reduction via Machine Learning-Accelerated First-Principles Calculations
Sahil Kumar, Adithya Maurya K R and Mudit Dixit
Understanding and optimizing polysulfide adsorption and conversion processes are critical to mitigating shuttle effects and sluggish redox kinetics in lithium-sulfur batteries (LSBs). Here, we introduce a machine-learning-accelerated framework, Precise and Accurate Configuration Evaluation (PACE), that integrates Machine Learning Interatomic Potentials (MLIPs) with Density Functional Theory (DFT) to systematically explore adsorption configurations and energetics of a series of N6-coordinated dual-atom catalysts (DACs). Our results demonstrate that, compared with single-atom catalysts, DACs exhibit improved LiPS adsorption and redox conversion through cooperative metal-sulfur interactions and electronic coupling between adjacent metal centers. Among all DACs, Fe-Ni and Fe-Pt show optimal catalytic performance, due to their optimal adsorption energies (-1.0 to -2.3 eV), low free-energy barriers (<=0.4 eV) for the Li2S2 to Li2S conversion, and facile Li2S decomposition barriers (<=1.0 eV). To accelerate catalyst screening, we further developed a machine learning (ML) regression model trained on DFT-calculated data to predict the Gibbs free energy (\Delta G) of Li2Sn adsorption using physically interpretable descriptors. The Gradient Boosting Regression (GBR) model yields an R^2 of 0.85 and an MAE of 0.26 eV, enabling the rapid prediction of \Delta G for unexplored DACs. Electronic-structure analyses reveal that the superior performance originates from the optimal d-band
alignment and S-S bond polarization induced by the cooperative effect of dual metal centres. This dual ML-DFT framework demonstrates a generalizable, data-driven design strategy for the rational discovery of efficient catalysts for next-generation LSBs.
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Materials Science · Cross-listed from cond-mat.soft
Friction-controlled reentrant aging and fluidization in granular materials
Ye Yuan, Walter Kob and Hajime Tanaka
Granular materials densify under repeated mechanical perturbations, a nonequilibrium dynamics that underlies many natural and industrial processes. Because granular relaxation is governed by frictional contacts and energy dissipation, this aging behavior fundamentally differs from that of thermal glasses despite their apparent similarities. Here, we uncover how friction controls the compaction dynamics of granular packings subjected to cyclic shear. Using discrete element simulations, we construct a dynamic state diagram as a function of strain amplitude and friction, revealing a rich interplay between jamming marginality, stabilization, and fluidization. We identify a friction-dependent crossover strain that separates aging and fluidized regimes, showing reentrant, non-monotonic behavior: Increasing friction first suppresses fluidization, then promotes it through smooth, creep-like rearrangements. This transition is marked by a shift from intermittent, avalanche-like rearrangements to continuous, diffusive motion. Our findings demonstrate that friction exerts a dual role in granular aging – both stabilizing and fluidizing – thereby uncovering the fundamental nonequilibrium mechanisms that govern compaction, rheology, and aging in athermal disordered systems. More broadly, our results reveal a general principle for how friction governs metastability and flow in athermal matter – from granular and frictional colloids to soils and seismic faults – linking microscopic contact mechanics to macroscopic dynamics.
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Materials Science
Dielectric Deposition Enhanced Crystallization in Atomic-Layer-Deposited Indium Oxide Transistors Achieving High Gated-Hall Mobility Exceeding 100 cm2/Vs at Room Temperature
Chen Wang, Kai Jiang, Jinxiu Zhao et al. (+4 more)
In this work, we report high-performance atomic-layer-deposited indium
oxide (In2O3) transistors with high gated-
Hall mobility ({\mu}H) exceeding 100 cm2/Vs at room temperature (RT). It is found that the deposition of top hafnium
oxide (HfO2) above the In2O3 channel significantly enhances its crystallization, leading to an average grain size of 97.2 nm in a 4.2-nm In2O3 channel. The ALD of In2O3 exhibits an epitaxy-like growth behavior, with its (222) planes aligning parallel to the (111) planes of both the top and bottom HfO2 dielectrics. As a result, bottom-gate In2O3 transistors with a high {\mu}H of 100.9 cm2/Vs and a decent subthreshold swing (SS) of 94 mV/dec are achieved by gated-
Hall measurement at RT. Furthermore, the devices maintain excellent performance at low temperatures, achieving a {\mu}H of 162.2 cm2/Vs at 100 K. Our study reveals the critical role of dielectric deposition induced crystallization in enhancing carrier transport and offers a scalable pathway toward high-mobility devices.
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All authors Chen Wang, Kai Jiang, Jinxiu Zhao, Ziheng Wang, Guilei Wang, Chao Zhao, Mengwei Si
Materials Science · Cross-listed from cond-mat.mes-hall
Altermagnetism induced surface Chern insulator
Xuance Jiang, Sayed Ali Akbar Ghorashi, Deyu Lu et al. (+1 more)
We propose a new pathway to the quantized anomalous
Hall effect (QAHE) by coupling an altermagnet to a topological crystalline
insulator (TCI). The former gaps the topological surface states of the TCI, thereby realizing the QAHE in a robust and switchable platform with near- vanishing magnetization. We demonstrate the feasibility of this approach by studying a slab of the TCI SnTe coupled to an altermagnetic RuO2 layer. Our first-principles calculations reveal that the d-wave altermagnetism in RuO2 induces a 7 meV gap to the Dirac surface states on the (110) surface of SnTe, producing a finite anomalous
Hall effect. Our approach generalizes to broader classes of altermagnetic materials and TCIs, thereby providing a family of topological altermagnetic
heterostructures with small or vanishing magnetization that support nontrivial Chern numbers. Our results highlight a promising new topological platform with great tunability and applications to spintronics.
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All authors Xuance Jiang, Sayed Ali Akbar Ghorashi, Deyu Lu, Jennifer Cano
Materials Science
Ab-initio study of structural, vibrational and non-linear optical properties of (TiO2)-(Tl2O)-(TeO2) glasses
Raghvender Raghvender, Assil Bouzid, Evgenii M. Roginskii et al. (+4 more)
This paper reports on a systematic first-principles molecular dynamics investigation of binary (TlO$_{0.5}$)$_{y}$-(TeO$_2$)$_{1-y}$ and ternary $(TiO$_{2}$)$_{x}$-(TlO$_{0.5}$)$_{y}$-(TeO$_2$)_{1-x-y}$ tellurite glasses. The obtained structural models are validated against available measured X-ray pair distribution functions. In the binary system, increasing TlO$_{0.5}$ content induces network depolymerization through the reduction of Te coordination number, the substitution of Te-O-Te linkages with Te=O$^{-}$...Tl$^{+}$ units, and the proliferation of non-bridging oxygens. In addition, rings analysis demonstrates a loss of the network connectivity via the opening of small n-membered rings. In contrast, TiO$_2$ acts as a network former in ternary glasses, preserving Te coordination number, and promoting a high fraction of bridging oxygens. Ti atoms induces a network repolymerization that manifests through the formation of smaller Ti-containing n-membered rings thereby balancing the strong effect of Tl$_2$O modifier. Beside the structural analysis, we also computed Raman spectra and non-linear optical properties on the obtained large periodic models. Our results reproduce experimental trends in Raman band shifts with composition, while nonlinear optical calculations show that <$\chi^{(3)}$> remains stable with TlO$_{0.5}$ addition in binary glasses, consistent with experiment. In the case of ternary systems, we find that the inclusion of a small fraction of TiO$_2$ preserves the high optical nonlinearity of the TeO$_2$ network while maintaining the overall network connectivity. These results establish a predictive framework for tailoring the atomic structure and nonlinear optical response of tellurite glasses through the controlled interplay of modifiers nature and concentration.
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All authors Raghvender Raghvender, Assil Bouzid, Evgenii M. Roginskii, David Hamani, Olivier Noguera, Philippe Thomas, Olivier Masson