Materials Science · Cross-listed from nlin.PS
Localization region detection with directionality estimation in a two-dimensional hexagonal crystal lattice model
Filips Kozirevs and Jānis Bajārs
This work is devoted to data-driven identification of discrete breathers in numerical simulations of a two-dimensional
crystal lattice using locally sampled wave data. Different
lattice wave
datasets are considered, with data collected from regions of different shapes and sizes defined by the
lattice particles in mechanical
equilibrium. Specifically, in addition to regions with a regular hexagonal shape, one- and quasi-one-dimensional regions reflecting the quasi-one-dimensionality of discrete breathers in two-dimensional hexagonal
crystal lattices are proposed. To improve numerical efficiency,
dataset dimensionality is reduced using Principal Component Analysis, and highly accurate Support Vector Machine classifiers are trained to distinguish between linear and nonlinear wave data. The obtained classifiers, together with the sliding window method, are applied to detect localization regions in two-dimensional hexagonal
crystal lattice numerical simulations. High-precision
algorithms for detected localization region
segmentation and localized wave directionality estimation within the detected regions are further proposed, and their performance is evaluated. The presented methods are successfully applied to detect localized waves and their collision regions, as well as their directionality, performing a numerical study of stationary and traveling two-dimensional discrete breather interactions. Qualitatively better results are obtained when considering wave-data collection regions respecting the quasi-one-dimensional nature of two-dimensional discrete breathers in the hexagonal
crystal lattice model.
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Materials Science · Cross-listed from quant-ph
Constraint-Aware Quantum Optimization of Defect Configurations in Doped ZrO2: XY-Mixer QAOA and Grover Adaptive Search
Huajing Song
Quantum optimization offers a route to searching the large defect-configuration spaces that arise in materials design. We develop an end-to-end, constraint-aware
quantum optimization workflow for composition-defect search in a doped ZrO2 thermal-barrier-coating (TBC) material system, using a MACE-MPA-0 energy
dataset to fit a 24-variable QUBO over 8 cation-occupation and 16 oxygen-vacancy variables with exactly two rare-earth substitutions and one oxygen vacancy, yielding 448 feasible configurations. The QUBO surrogate reproduces the MACE energies with held-out R2 = 0.997 (full-data R2 = 0.999, RMSE = 17 meV). We validate two complementary
quantum pathways against exact enumeration: a constraint-preserving XY-mixer QAOA that confines sampling to the feasible subspace and places 86% of probability mass within 1 meV of the MACE optimum at depth p = 3, and a fault-tolerant constrained Grover Adaptive Search oracle with explicit fixed-point arithmetic, branch-safe comparison, feasibility checking, and phase kickback. Across threshold cases, the validated oracle uses 324 high-level logical
qubits, or 352 to 358 with conservative clean-ancilla v-chain accounting, and requires 3.6 to 4.3 x 104 Toffoli gates per Grover (GAS) iteration. An idealized feasible-space amplification estimate suggests up to a 240x reduction in total Toffoli cost relative to the full 224 occupation space, providing a resource-estimation bridge between materials-informed QUBO modeling, constraint-aware QAOA, and fault-tolerant threshold search.
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Materials Science · Cross-listed from cond-mat.str-el
Evolution of anisotropic magnetostriction in LaMn1-xCoxO3 (x= 0.1-0.9)
M. Manikandan and R. Mahendiran
Polycrystalline samples of LaMn1-xCoxO3 series over a wide compositional range (x = 0.1 - 0.9) were synthesized by microwave irradiation of
oxide precursors and their
magnetic and magnetostrictive properties were investigated. Magnetostrictions parallel (l_par) and perpendicular (l_per) to the applied
magnetic field were measured to estimate anisotropic(l_anis) and volume magnetostrictions(l_vol). In all the compositions, l-par (l_per) is negative (positive) and (l_anis) >> (l_vol), suggesting dominance of anisotropic
lattice distortion under a
magnetic field. The value of l_anis at 10 K for H = 50 kOe initially increases with x from 178 ppm for x = 0.1 to a maximum of 1221 ppm at x = 0.5 before decreasing for higher x. The composition dependence of magnetostriction is asymmetric about x = 0.5, the decrease for x > 0.5 is more steeper than for x < 0.5 whereas saturation magnetization decreases monotonically with increasing x except for an abrupt change at x = 0.6. The largest anisotropic magnetostriction observed for x = 0.5 is attributed to the presence of high-
spin Co2+ ions with a non-zero orbital moment in the maximum fraction whereas Mn3+/4+ or Co3+ ions play minor roles. The composition dependence of magnetostriction is suggested to arise from changes in the structure, valence states of Mn and Co ions and
magnetic interactions among them.
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Materials Science · Cross-listed from physics.app-ph
Defect-Width-Tunable Resonant Elastic-Wave Transmission in Micro-Pillar Arrays
Alok Pokharel
Periodic micro-pillar
lattices integrated on elastic substrates provide a promising plat-form for controlling elastic-wave propagation through localized resonant interactions. In this work, defect-engineered resonant transmission in periodic tungsten micro-pillar arrays deposited on silicon substrates is numerically investigated using finite-element simulations. Two-dimensional frequency-domain analyses were performed to evaluate the influence of one-, two- and three-pillar defects on elastic wave transmission characteristics. The results reveal strong defect-width-dependent transmission modulation together with the localized resonant elastic-wave redistribution within the periodic
lattice. Full three-dimensional simulations further confirm the presence of defect-sensitive resonant localization and modified elastic-wave transport pathways. Floquet dispersion analysis of a periodic unit
cell reveals multiple nearly flat resonant branches associated with low-group-velocity elastic-wave modes, indicating predominantly subwavelength locally resonant behavior. A comparative study between tungsten and copper resonators demonstrates enhanced resonant confinement in tung-sten-based structures due to their larger inertial contrast with the supporting sub-strate. The proposed defect-engineered micro-pillar
lattices provide an effective approach for frequency-selective elastic-wave control and localized resonant wave ma-nipulation in elastic metamaterial systems.
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Materials Science · Cross-listed from cond-mat.str-el
Magnetovolume effect in SrRu1-xCoxO3 (x = 0.0, 0.05)
M. Manikandan and R. Mahendiran
Polycrystalline SrRu1-xCoxO3 (x = 0.0, 0.05) and CaRuO3 were rapidly synthesized (< 1 hour) by microwave irradiation of
oxide powders, and their
magnetic, magnetoresistance, thermal expansion, and magnetostriction properties were investigated. The microwave-synthesised SrRuO3 exhibits a
ferromagnetic transition at TC = 160 K, metallic-type resistivity, and negative magnetoresistance, with magnitudes comparable to those of a sample synthesized by conventional heating over 24 hours. Upon lowering the temperature from 300 K, the linear thermal expansion shows a transition from the usual contraction in the paramagnetic state to spontaneous expansion in the
ferromagnetic state (invar-like effect). The application of an external
magnetic field at a fixed temperature results in isotropic expansion of the length, implying a positive magnetovolume effect. The volume magnetostriction is 40 ppm at 10 K in a
magnetic field of 50 kOe, and it reaches a maximum value of 60 ppm close to TC. The spontaneous thermal expansion is diminished in SrRu0.95Co0.05O3. While the magnetostriction is anisotropic at 10 K, the isotropic behaviour is recovered above 80 K, and the maximum value of the positive magnetovolume is comparable to that of the parent compound. Our results suggest that the magnetovolume effect in SrRu1-xCoxO3 is related to competition between robust tilting/rotation of RuO6 octahedra and
spin-orbit interaction of the doped Co2+ ions
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Materials Science · Cross-listed from cond-mat.str-el
Van Hove Singularity and Phase Instability: Exploring the Role of Electron Correlation in the Magnetic Behavior of $\mathrm{Fe}_{16}\mathrm{N}_2$
Peter Stoeckl, Przemyslaw Wojciech Swatek and Jian-Ping Wang
The ordered iron nitride phase $\alpha''-\mathrm{Fe}_{16}\mathrm{N}_2$ is a promising candidate for environment-friendly, rare-earth-free permanent magnets due to its demonstrated
giant saturation magnetization ($M_s$). However, first-principles electronic-structure calculations have struggled to consistently reproduce experimentally-observed high $M_s$, and have yielded highly variable magneto-crystalline anisotropy (MCA) values. In this work, we employ Density Functional Theory under the GGA+$U$ framework to study the effect of the Hubbard parameters $U$ and $J$ on the
magnetic properties of $\mathrm{Fe}_{16}\mathrm{N}_2$. We demonstrate that the electronic structure exhibits high sensitivity to these parameters, specifically uncovering a van Hove singularity near the
Fermi level ($E_F$), inherently tied to the material's structural and thermal phase instability. By linking this topological anomaly to the calculated
magnetic properties, we demonstrate that the selection of $U$ not only tunes $M_s$ and MCA energy towards experimental values but also reveals an underlying electronic mechanism potentially responsible for the phase's metastability. This provides a framework for understanding the correlation-driven
magnetic behavior of $\mathrm{Fe}_{16}\mathrm{N}_2$ and offers a pathway for optimizing its stability and performance in practical applications.
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Materials Science
Delafossites as an unexpected competing phase to infinite-layer oxides
Armin Sahinovic, Benjamin Geisler and Rossitza Pentcheva
Motivated by the discovery of superconductivity in Sr-doped infinite-layer nickelate films on SrTiO$_3$(001), we explore the broader landscape of $AB$O$_2$
oxides through comprehensive high-throughput first-principles simulations. Specifically, delafossites and their ordered rock-salt (111) variants stand out as intriguing layered
oxides that share the infinite-layer $AB$O$_2$ stoichiometry and simultaneously retain a perovskite-like octahedral motif. This positions them as a unique structural bridge between these two phases and as promising candidates for novel correlated electronic states. We compile a phase diagram that compares the relative stability of these four distinct
oxides across the periodic table. Surprisingly, we find that the delafossite structure rivals the infinite-layer phase in thermodynamic stability for the nickelates, and even more for the recently suggested palladate and platinate analogs. Comparison of the respective electronic structures reveals that the delafossite compounds, which we find to be characterized by reversed cation order, exhibit a strongly $d_{z^2}$-dominated
Fermi surface, in stark contrast to the $d_{x^2-y^2}$ character observed in the infinite-layer phases. Among all candidates, the La-Ni combination stands out as a thermodynamic optimum for stabilizing the infinite-layer motif. Furthermore, we show that hole doping via Ca, Sr, and Ba systematically enhances the stability of the infinite-layer phase in all three transition-metal families. These results reveal fundamental challenges in realizing bulk substrate-free infinite-layer
oxides, and simultaneously offer guidance for future experimental synthesis efforts targeting novel superconducting compounds.
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Materials Science · Cross-listed from cond-mat.mes-hall
Non-equilibrium angular momentum selectivity and filtering in chiral carbon nanotubes
Sergio Shmayev, D. R. da Costa and D. A. Bahamon
Carbon nanotubes (CNTs) constitute a highly tunable platform for probing the interplay between structural chirality and
quantum transport in quasi-one-dimensional systems. Here, we perform a systematic study of the non-
equilibrium orbital response across a broad set of metallic and semiconducting
chiral CNTs. We find that the orbital Edelstein susceptibility depends strongly on both chirality and nanotube diameter, revealing that the orbital response cannot be captured by a universal scaling law. Instead, distinct families of CNTs emerge, forming characteristic orbital-response branches uniquely determined by the
chiral wrapping vector. We further investigate the role of metallic contacts on orbital-current generation and orbital selectivity. While metallic CNTs rapidly recover their intrinsic orbital response away from the contact region, semiconducting CNTs display pronounced oscillatory behavior arising from interference between transport channels carrying different angular momenta injected by wide-band metallic contacts. Finally, by incorporating angular correlations into the contact self-energy, we demonstrate that
chiral CNTs can operate as efficient orbital-angular-momentum filters, selectively transmitting orbitally textured electronic states in accordance with the
crystal angular momentum of the propagating bands.
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Materials Science
Fine-Tuned Machine-Learned Interatomic Potentials for Structural and Vibrational Properties of Twisted 2D Materials
Viet-Anh Tran, Viet-Hung Nguyen, Wei Chen et al. (+2 more)
Twisted van der Waals
bilayers form moiré superlattices whose structural and vibrational properties are highly sensitive to variations in local stacking registry and the degree of atomic reconstruction, yet accurate atomistic modeling of these systems at the DFT level remains computationally prohibitive at small twist angles. We investigate machine-learned interatomic potentials for moiré systems, using twisted
bilayer graphene, h-BN, and MoS$_2$ as representative materials spanning a broad spectrum of mechanical compliance and atomic reconstruction behavior. We show that fine-tuning universal atomistic foundation models is essential to achieve DFT accuracy for layered materials, as broadly trained foundation models prove insufficient for resolving the subtle interlayer energetics that govern atomic reconstruction. Through local strain tensor analysis and the
phonon band unfolding technique, our fine-tuned MACE model reveals a consistent reconstruction-induced strain landscape in all three materials, with extended low-energy stacking domains separated by narrow
soliton lines where deformation concentrates. The system progressively optimizes the local stacking registry within each domain, giving rise to a spatially structured deformation field whose amplitude scales with the mechanical compliance of the material and can be further tuned by external perturbation. The obtained results of both atomic reconstructed structures and moiré
phonon spectra present a good agreement with the reported experiments, thereby demonstrating the accuracy and efficiency of our methodology in modeling of these large scale nanomaterials.
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All authors Viet-Anh Tran, Viet-Hung Nguyen, Wei Chen, Gian-Marco Rignanese, Jean-Christophe Charlier
Materials Science
Open-quantum-system theory of non-Markovian electron-phonon dynamics
Gabriele Riva, Jacopo Simoni and Yuan Ping
We present a non-Markovian open-
quantum-system formalism for nonequilibrium electron-
phonon dynamics: a closed set of five coupled equations of motion, derived directly from the density
matrix, in which
memory, dissipative broadening, and coherent-
phonon dynamics arise on an equal footing without two-time correlators. It recovers the Fan-Migdal, RPA-polarization, and Ehrenfest self-energies and the Lindblad and Boltzmann limits. In the strongly driven Holstein dimer it separates the coherent polaronic peak, of Ehrenfest origin, from the linewidths and multiphonon structure of Fan-Migdal origin.
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Materials Science · Cross-listed from astro-ph.HE
Crust glass formation reveals the neutron star birth properties in IGR J17480-2446
D. A. Baiko and A. I. Chugunov
IGR J17480-2446 is a low-mass X-ray binary, harboring an exceptional accreting
pulsar (a
neutron star) with an unusual
spin frequency of 11 Hz and a very slow post-outburst crust cooling. The former may imply that it is observed at an early stage of recycling, while the latter was shown to indicate the presence in the outer crust of a low thermal conductivity layer, possibly made of glass. Here we argue that the glass layer formation is a natural result of
accretion induced failure of pristine cold
crystal crust. This allows us to determine the mass of the accreted material as $\Delta M \approx 2.4\times 10^{-6}~M_\odot$, confirming very early
accretion stage for this
neutron star. An analysis of
spin and thermal state reveals a peculiar set of
neutron star birth properties which is commonly associated with `recycled'
neutron stars, i.e.\ those that have been experiencing prolonged periods of
accretion from a companion. We speculate that such birth properties may represent the outcome of
neutron star formation in an electron-capture
supernova.
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Materials Science
A correlation of structural changes with nanomechanical properties in TiN-AlN multilayer films
Nidhin George Mathews, Aidan A. Taylor, Johannes Zechner et al. (+5 more)
The present work investigates the changes in overall nanomechanical properties of reactively sputtered TiN-AlN multilayer films arising due to phase transformation in the AlN layers. Multilayered TiN-AlN films were sputter deposited with constant TiN layer thickness of 5 nm while the AlN layer thickness varied between 1-5 nm. The AlN underwent a phase transition from cubic rock salt to hexagonal wurtzite above 3 nm thickness due to the
lattice strains. The hardness and indentation modulus of the multilayers decreased with increasing AlN film thickness, up to 3 nm, due to increased volume fraction of softer AlN layer and then stabilized for 4 nm and 5 nm thickness films. Micropillar compression of these multilayers showed a transition from columnar brittle to partially ductile failure associated with crack deflection with increasing AlN film thickness. Interestingly, nanoindentation scratch resistance of 3 nm AlN multilayer was observed to be superior compared to all other films. The crack propagation behavior in scratching showed increased microcracking tendency towards higher AlN film thickness. This shows that cubic to hexagonal transformation in AlN is beneficial for improving the damage tolerance of the multilayer system.
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All authors Nidhin George Mathews, Aidan A. Taylor, Johannes Zechner, Helmut Riedl, Paul H. Mayrhofer, Johann Michler, Vipin Chawla, Gaurav Mohanty
Materials Science · Cross-listed from physics.class-ph
On Potentials and Complementary Potentials in One-Dimensional Nonlocal Integral Formulations
Marko Čana{\dj}ija and Ante Skoblar
The present research presents potentials and complementary potentials used in the one-dimensional nonlocal integral formulations. The pure stress and the pure strain nonlocal formulations were considered. While the potential used in the strain driven formulation is well known, the complementary potential has not yet been presented in the literature. The same applies to the stress driven formulation. The equivalent formulations are obtained by resorting to the Legendre transformation, and their equivalence is proved. It is also shown that these results can be used to postulate a novel potential, i.e. a kind of mixed stress-strain potential, which is, however, as ill-conditioned as the pure strain-driven formulation. Finally, an example is given that practically confirms that the stress-driven formulations resulting from the potential and the complementary potential are equivalent.
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Materials Science
Cladding Layer Enhanced GHz Bulk Acoustic Wave Resonance in Sodium Niobate Thin Films on Silicon
Zhi Shiuh Lim, Qibin Zeng, Hui Kim Hui et al. (+17 more)
Bulk acoustic wave resonators (BAWR) and bandpass filters operating at GHz frequency are the workhorse of (Vo-)LTE telecommunication and broadband internet. In line with the Singapore Green Plan 2030 for innovating environmentally friendly products, we fabricated lead-free BAWR with sodium niobate (NaNbO3) piezoelectric on silicon with a high electromechanical coupling factor up to 31.3% operating at ~4 GHz. We disclose our crucial strategy where the NaNbO3 layer is cladded between two thin layers of high band gap
insulators, which satisfies two primary objectives, i.e. leakage current mitigation and crack avoidance. In addition, we also verified the efficacy of reducing
lattice parameters of the cladding layers in promoting vertically distorted tetragonal phase NaNbO3 and producing stronger BAWR signals.
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All authors Zhi Shiuh Lim, Qibin Zeng, Hui Kim Hui, Mengyao Xiao, Tiancheng Luo, Weifan Cai, Shengwei Zeng, Samantha Faye Duran Solco, Baichen Lin, Celine Sim, Zhen Ye, Jinlong Xu, Mingxi Chen, Wei Fu, Chee Kiang Ivan Tan, Seeram Ramakrishna, Yeng Ming Lam, Vincent Chengkuo Lee, Ariando Ariando, Huajun Liu
Materials Science
Reversible nonrelativistic magnon spin transport in ferroelastic altermagnets
Haozhou Cai, Jian Wu and Weiyi Pan
Magnons in
antiferromagnetic (AFM)
insulators facilitate low-dissipation, stray-field-free
spin transport. However, achieving nonvolatile, field-free control over
magnon spin currents remains elusive. Here, based on
symmetry analysis, we propose a universal mechanism for the active manipulation of
magnon spin transport via ferroelastic transitions in two-dimensional (2D) altermagnets (AMs)-a class of unconventional AFMs simultaneously exhibiting compensated magnetization and nonrelativistic
spin splitting. We show that these transitions effectively reorient principal
crystal axes and modulate the underlying
magnetic exchange anisotropy. Consequently, this magnetoelastic coupling drives nonrelativistic anisotropic
spin transport that is ferroelastically switchable without the need for external
magnetic fields or Berry
curvature, leading to sign reversals in the
spin Seebeck and
spin Nernst conductivities. We validate this mechanism using first-principles calculations and
spin-model analyses of an AM CoTe2 monolayer. Our findings establish a
symmetry-based magnetoelastic paradigm for the nonvolatile control of
magnon spin transport in 2D AMs, opening new avenues toward energy-efficient, reconfigurable AFM magnonic devices.
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Materials Science
Bridging Phase-Field Model and Deep Learning for Predicting 2D and 3D Microstructure Evolution in Ternary Alloys
Owais Ahmad, Aravind K, Naveen Kumar et al. (+3 more)
We develop a hybrid framework that integrates a phase-field model (PFM) with an
attention-enhanced deep learning (DL) architecture to study ternary spinodal dealloying, a sophisticated self-organization approach used to fabricate three-dimensional bicontinuous, hierarchical nanoporous materials. The study captures three distinct phase-separation mechanisms that emerge during the early stages of spinodal decomposition in both two and three dimensions. The DL workflow consists of three key components: (i) a dimensionality-reducing autoencoder that provides compact representations of high-resolution microstructure images (256x256x3), (ii) an
attention-augmented convolutional long short-term
memory (ConvLSTM) network that learns complex spatiotemporal correlations governing microstructure
evolution, and (iii) a novel slice-by-slice strategy that enables extension of the model to three-dimensional systems (128x128x128x3). We further demonstrate a hybrid simulation strategy in which PFM accurately captures rapid early-stage microstructure
evolution, while the DL model efficiently predicts late-stage coarsening dynamics. The trained DL model achieves remarkable predictive accuracy, maintaining fidelity up to 400 timesteps ahead and generalizing to compositions outside the training distribution. By bridging the physical fidelity of PFM with the computational efficiency of DL, this framework establishes a robust platform for predictive modeling of microstructure
evolution in complex multicomponent systems.
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All authors Owais Ahmad, Aravind K, Naveen Kumar, T.A. Abinandanan, Somnath Bhowmick, Rajdip Mukherjee
Materials Science · Cross-listed from cond-mat.mes-hall
Superconducting cavity probes sliding ferroelectricity in small-angle twisted WSe$_2$
Krishnendu Maji, Supriya Mandal, Sriram H. et al. (+8 more)
Ferroelectricity is a property of materials that exhibit spontaneous charge polarization. Ferroelectricity in 2D materials is interesting because of their applications in
memory devices and field-effect transistors. Recently, a new type of ferroelectricity, known as sliding ferroelectricity, has been discovered, in which parallel-stacked
bilayers of hexagonal boron nitride (hBN) or transition metal dichalcogenides (TMDCs) develop an out-of-plane electric polarization. In this work, we probe the polarization of small-angle parallel stacked WSe$_2$ by measuring its high-frequency AC response, achieved by
embedding it into a half-wave superconducting coplanar waveguide cavity. We observe a hysteretic response in the capacitance of the stack and quality factor of the cavity, confirming ferroelectric switching in the system. Our results further reveal relaxation effects associated with ferroelectric domain-wall motion. This cavity-based technique has potential applications in probing domain-wall dynamics in a ferroelectric system at high frequencies.
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All authors Krishnendu Maji, Supriya Mandal, Sriram H., Rishiraj Rajkhowa, Malhar Date, Sayani Pal, Meghan P. Patankar, Kenji Watanabe, Takashi Taniguchi, Vibhor Singh, Mandar M. Deshmukh
Materials Science
First-principles study of the impact of As doping on the structural and electronic properties of MoS$_2$ monolayer
A. Daouadi and M. L. Benkhedir
This study is aimed at exploring the structural and electronic properties of doped MoS$_2$ monolayers, including Mo and S vacancies and As doped systems, employing DFT calculations. The electronic properties were analyzed to understand how these modifications affect the behavior of the material. Introduction of defects generates new defect states in the midgap. In the S-vacancy (V$_\text{S}$), Mo-vacancy (V$_{\text{Mo}}$), As-Mo (As substituting Mo), and As-S (As substituting S) doped systems, the downward shift of the
Fermi level to the valence band indicates a $p$-type behavior. In the As interstitial system the
Fermi level shifts to the conduction band, suggesting an $n$-type
semiconductor. The results highlight that doping MoS$_2$ with As, particularly at the Mo site, can be used in photocatalysis and high-efficiency photovoltaics. Additionally, the As interstitial system demonstrates an enhanced performance in field-effect transistors (FETs).
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Materials Science · Cross-listed from math-ph
Electromagnetic Characterization of Magnetic Bar: Case of Square Cross-Section Shape
Taha El Hajji, Bruno Ricardo Marques and Lars Sjöberg
This paper presents a complete two-dimensional theoretical model for the electromagnetic behavior of square-section solid
magnetic bars under sinusoidal loading. Through the application of Maxwell's equations within a Cartesian coordinate system and the integration of complex permeability, exact mathematical expressions are derived for mutual impedance, internal
magnetic fields, flux, and core losses.
Hyperbolic functions are utilized to separate the variables, enabling the accurate representation of edge flux accumulation and the 2D skin effect. In addition to mathematically decoupling eddy current and hysteresis losses, this formulation yields a new apparent permeability parameter. This parameter establishes a fast, reliable method for
magnetic steel characterization that bypasses the extensive processing times associated with Finite Element Analysis (FEA). Numerical results over 1 Hz-1 MHz show the apparent relative permeability decreasing from 500 to 300 and a characteristic resistance peak near 700 kHz, marking the transition from volumetric to surface-dominated loss regimes.
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Materials Science · Cross-listed from cs.CV
Accurate identification and measurement of the precipitate area by two-stage deep neural networks in novel chromium-based alloys
Zeyu Xia, Kan Ma, Sibo Cheng et al. (+7 more)
The performance of advanced materials for extreme environments is underpinned by their microstructure, including the size and distribution of reinforcing phases. Chromium-based superalloys are a recently proposed alternative to conventional face-centred-cubic superalloys for high-temperature applications, such as Concentrated
Solar Power, and their development requires efficient measurement of precipitate volume fraction and size distribution from electron microscopy images. Traditional fixed-threshold image processing is sensitive to background noise, generalises poorly across materials, and requires substantial manual measurement effort. To address these bottlenecks, this study proposes DT-SegNet, an end-to-end two-stage deep learning scheme based on YOLOv5 and SegFormer for object detection and
segmentation in electron microscopy images. The approach combines the training efficiency of convolutional neural networks at the detection stage with the
segmentation accuracy of a
Vision Transformer. Numerical experiments show that DT-SegNet substantially outperforms state-of-the-art
segmentation tools offered by Weka and ilastik across metrics including accuracy, precision, recall, and F1-score. The model provides a useful tool for
alloy-development microstructure examinations and helps address the large
datasets associated with high-throughput
alloy development.
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All authors Zeyu Xia, Kan Ma, Sibo Cheng, Thomas Blackburn, Ziling Peng, Kewei Zhu, Weihang Zhang, Dunhui Xiao, Alexander J Knowles, Rossella Arcucci
Materials Science
Halide substitution effects on the photovoltaic properties of Ca$_3$PX$_3$ (X = F, Cl, Br, I) perovskites: advancing solar cell efficiency
P. Dhariwal, D. Prakash, K. D. Verma et al. (+3 more)
Herein, the fundamental physical characteristics like structural, electronic, optical parameters of the Ca$_3$PX$_3$ (X = F, Cl, Br, I) materials have been investigated for their potential optoelectronic applications, particularly for
solar cells and related devices. To the crystallographic investigations, Ca$_3$PI$_3$ has the most stable configuration among all investigated materials. From the band structure analyses of these materials indicate that all materials have a direct bandgap in the range of 2.0 eV to 3.788 eV, which makes them ideal for light absorption. For the photovoltaic applications, we have analysed first-principles spectroscopic screening limited maximum efficiency (SLME) which confirms that the Ca$_3$PI$_3$ material exhibits the highest
solar cell efficiency 29.6% and Ca$_3$PF$_3$ and shows lower efficiency for
solar cell suitability 0.6%. Thus, these results demonstrate the real potential and abilities of halide substitution to tune the materials for particular optoelectronic devices.
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All authors P. Dhariwal, D. Prakash, K. D. Verma, A. Kumari, P. K. Kamlesh, A. S. Verma
Materials Science
Spin-orbit-enabled Fermi-surface splitting in noncollinear antiferromagnetic SmBi
Long Zhang, Ming Cheng, Jingyu Li et al. (+10 more)
Spin-split electronic structures in compensated antiferromagnets are commonly sought in the nonrelativistic limit, where
magnetic order lifts
spin degeneracy without
spin-orbit coupling (SOC). Whether SOC can instead be the indispensable
symmetry-breaking ingredient remains largely unexplored. Here we combine
quantum oscillations detected by ultrahigh-sensitivity ac magnetostriction,
magnetic-
symmetry analysis and first-principles calculations to resolve the bulk
Fermi-surface
evolution of SmBi across two successive
antiferromagnetic (AFM) transitions. New oscillation branches emerge below TN and undergo a further reconstruction below T*, whereas isostructural SmSb shows no comparable change. For the candidate noncollinear orders of SmBi, breaking global parity-time
symmetry is insufficient in the nonrelativistic limit because residual
spin-space
symmetries protect twofold band degeneracy; conversely, SOC alone cannot lift the degeneracy of the centrosymmetric paramagnetic (PM) phase. Only the coexistence of noncollinear order and SOC locks
spin to the
lattice and removes the residual protection. SmBi therefore realizes a cooperative, relativistic route to
spin-split
Fermi surfaces, broadening unconventional magnetism beyond systems whose splitting is already present in the nonrelativistic limit.
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All authors Long Zhang, Ming Cheng, Jingyu Li, Honghao Wan, Xiaoyuan Zhou, Mingquan He, Aifeng Wang, Yuping Sun, Dong-Hui Xu, Huixia Fu, Youguo Shi, Xuan Luo, Yisheng Chai
Materials Science
Sliding ferroelectricity tunable conventional and anomalous spin Hall effects in bilayer 1T'-WTe2
Chao Wu, Pengqiang Dong, Kai Wei et al. (+2 more)
The
spin Hall effect, recognized for its high-speed, low-power, and highly controllable characteristics, is a key enabler for next-generation
memory and logic devices. However, a primary challenge lies in achieving 180$^{\circ}$ magnetization switching without an external
magnetic field in
spin-orbit torque devices. Here, we propose a method to tune the conventional and anomalous
spin Hall effects by the intrinsic sliding ferroelectricity. Importantly, the anomalous
spin Hall effect can enable the field-free switching of perpendicular magnetization. We find a substantial anomalous
spin Hall conductivity of $\sigma_{xy}^{y}$ = 45.62 ($\hbar$/e)S/cm and $\sigma_{yx}^{y}$ = 56.84 ($\hbar$/e)S/cm in monolayer 1T'-WTe$_2$. These values are significantly enhanced to $\sigma_{xy}^{y}$ = -96.77 ($\hbar$/e)S/cm and $\sigma_{yx}^{y}$ = 104.03 ($\hbar$/e)S/cm in the
bilayer 1T'-WTe$_2$. More interestingly, the sliding ferroelectricity enables reversible switching of the signs and magnitudes for both the conventional and anomalous
spin Hall conductivities. This originates from the fact that the sliding ferroelectric markedly shifts the relative
spin Berry
curvature contributions from the valence and conduction bands around the $\Gamma$-X path. Our findings not only reveal a strong coupling between sliding ferroelectricity and
spin transport, but also propose a strategy for the nonvolatile electrical control of spintronic devices.
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All authors Chao Wu, Pengqiang Dong, Kai Wei, Hanbo Sun, Ping Li
Materials Science
Stacking-Directed Polarization and Excitonic Engineering in MoS$_2$/MoSe$_2$ van der Waals Heterostructures
Mohammed El Amine Miloudi and Oliver Kühn
The stacking-dependent polarization and excitonic response of MoS$_2$/MoSe$_2$
heterostructures were investigated using GW+BSE many-body perturbation theory. While homobilayer MoS$_2$ exhibited a switchable interlayer dipole driven by registry-induced
symmetry breaking, the MoS$_2$/MoSe$_2$ hetero-interface remained pinned by the intrinsic chemical potential mismatch between sulfur and selenium. In 2L-MoS$_2$/MoSe$_2$ trilayers, the stacking sequence enabled a deterministic control of photogenerated electrons between the central and bottom MoS$_2$ layers, governed by internal electric fields and quasiparticle band-edge shifts of 60–70~meV. Our calculations predicted a 36~meV interlayer excitonic shift, in remarkable agreement with recent experiments. These results elucidate the microscopic link between atomic registry and many-body interactions, establishing transition metal dichalcogenide trilayers as a potential platform for sliding ferroelectricity and programmable optoelectronic functionalities.
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Materials Science · Cross-listed from physics.chem-ph
The impedance of a charged flat-plate electric double-layer capacitor
Adrian L. Usler, David Fertig and Mathijs Janssen
We calculate the impedance of a flat-plate electric double-layer (EDL) capacitor by means of Finite Element Method simulations of modified Poisson–Nernst–Planck equations. In Nyquist representation, the impedance spectra show a slanted line at intermediate frequencies if the capacitor is biased by a voltage, $U_\mathrm{bias}\neq 0$, or if the cation and anion
diffusion coefficients differ, $D_-\neq D_+$. By inspecting the concentration perturbations in the relevant frequency range, we confirm that the slanted line is in both cases related to ambipolar salt
diffusion. On the basis of our impedance data, we disprove two previously made claims: 1) that the width $R_\mathrm{sl}$ of the slanted-line region represents an EDL resistance; and 2) that the slope $k_\mathrm{sl}$ of the slanted line is a measure of the ratio of the
diffusion and charging time scales, $\tau_\mathrm{diff}/\tau_\mathrm{c}$. For the quantitative analysis of flat-electrode EDL capacitor impedance, we propose instead two equivalent
circuits, for the cases $D_-\neq D_+$ and $U_\mathrm{bias}\neq 0$. These two cases give rise to antisymmetric and symmetric salt perturbations, which are best described by a Warburg short and Warburg open element, respectively. From our
circuit analysis, we obtain quantitative relations that link the Warburg prefactors to the ambipolar
diffusion coefficient, the chemical capacitance of the bulk electrolyte, and the differential charge efficiency of the EDLs. We thus provide a theoretical framework that explains why the width of the slanted line saturates at large biases, why it vanishes for large ion packing fractions, and how the system's overall capacitance is limited by the finite amount of ions in a closed system.
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Materials Science · Cross-listed from physics.app-ph
Revisiting Theoretical Modeling of Seebeck Coefficient of Semiconductors
Yuchao Hua
We revisit the closed-form models of Seebeck coefficient, and identify the thermodynamic flaws in those extensively-used methodologies, essentially including the confusion of electrochemical potential and electrical potential within the definition, arbitrarily neglecting the dependence on conduction band bottom and
Fermi level when calculating distribution function spatial gradient, and the improper heat flux presentation. Here, an alternative methodology is presented, which derives the Seebeck coefficient model based on the drift-
diffusion equation with the Soret effect in the open
circuit condition. The reversible model that eliminates the electron velocity and relaxation terms in the formulation is recovered for the band term in the near-
equilibrium case, and it can give the lower bound of Seebeck coefficient in theory, while the
phonon-drag term is of the identical form to the Boltzmann transport equation(BTE)-based one. A case study is performed for highly-n-doped Silicon, where the reversible, ballistic(based on Landauer formulation) and BTE models are compared with each other and with the experimental data. The reversible model gives the fairly-good predictions for the experiments. Given its theoretical-soundness, simple form and low computation cost, the reversible model can serve as a concise alternative for evaluating thermoelectric properties in both the reversible and near-
equilibrium cases.
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