Materials Science · Cross-listed from cond-mat.soft
Interplay of network architecture and ionic environment in dictating pNIPAM microgel thermoresponsiveness
Syamjith KS and Alan Ranjit Jacob
The utility of non functionalized poly(N-isopropylacrylamide) (pNIPAM) microgels in physiological and environmental applications is strictly dependent on their reversible thermoresponsiveness and stability in saline media. Despite their importance, a unified understanding of how network
topology specifically crosslinker concentration and distribution regulates ionic sensitivity remains fragmented in the literature. This work systematically investigates the interplay between network
topology and ionic strength (0 to 100 mM NaCl) across eight distinct microgel architectures, ranging from ultra-low crosslinked (ULC) to core-corona and homogeneously crosslinked (HC) variants. Utilizing dynamic light scattering across 22 batches, we analyzed critical thermoresponsive properties, including volume phase transition temperature (VPTT) shifts, salt tolerance thresholds, hysteresis indices, and flocculation kinetics (only at extreme salinity, 1000 mM NaCl and at 25 deg C). This comprehensive investigation enables a multidimensional analysis of how ionic strength, the presence or absence of crosslinkers (MBA), spatial crosslinking distribution, and thermodynamic states dictate microgel behavior across varying temperatures. Finally, we evaluate the applicability of this experimental library to established theoretical frameworks, specifically the Flory Rehner and Flory Rehner Donnan models, addressing ongoing debates regarding their validity in describing complex microgel systems.
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Materials Science · Cross-listed from cs.DL
Benchmarking Cross-Scale Perception Ability of Large Multimodal Models in Material Science
Yuting Zheng, Zijian Chen and Qi Jia
Unraveling the hierarchical structure-property relationships is the central challenge of materials science, necessitating the interpretation of data across vast physical scales from micro to macro. Despite the rapid integration of Large
Multimodal Models (LMMs) into scientific workflows, existing scientific
benchmarks primarily focus on general chart interpretation or isolated common-sense
reasoning, failing to capture
reasoning ability across intricate physical dimensions. To address this, we introduce CSMBench, a
dataset comprising 1,041 high-quality figures curated from premier journals up to September 2025. CSMBench categorizes data into four scientifically distinct regimes: atomic, micro, meso, and macro scales, strictly aligning with the focus and definitions in materials study. Through open-ended figure description and multiple-choice caption matching tasks, we evaluate state-of-the-art open-source and closed-source models. Our analysis identifies that performance varies significantly across physical scales due to the distinct visual characteristics, highlighting the limitations of current generalist models and identifying critical directions for achieving hierarchical and accurate understanding in materials research. The CSMBench is publicly released at: https://huggingface.co/
datasets/lututu/CSMBench.
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Materials Science
Asymmetric Energy Landscapes Control Diffusion in Glasses
Ajay Annamareddy, Bu Wang, Paul M. Voyles et al. (+2 more)
While
diffusion in crystalline solids is quantitatively understood through defect-mediated atomic hops, no comparable quantitative framework exists for glasses. In these systems, the origin of large
diffusion activation energies remains puzzling, despite local rearrangements involving low barriers. Using molecular dynamics simulations of metallic glasses, we decompose
diffusion into random-walk and correlation contributions and find that back-and-forth correlated motion, not local rearrangement barriers, dominates the activation energy, resolving how low-barrier rearrangements yield large macroscopic activation energies. These correlations arise from asymmetry between forward and reverse barriers, a generic feature of disordered energy landscapes. We find that the correlation-driven mechanism is active beyond metallic glass
alloys, including SiO2 and a single-component Lennard-Jones glass. The latter demonstrates that the correlation originates from structural disorder rather than chemical complexity. The framework also explains accelerated surface
diffusion, where reduced activation energies arise primarily from weaker correlations rather than changes in local rearrangement barriers. Our results establish a direct, quantitative link between atomic-scale dynamics and macroscopic transport, providing a predictive basis for kinetics in disordered materials.
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All authors Ajay Annamareddy, Bu Wang, Paul M. Voyles, Izabela Szlufarska, Dane Morgan
Materials Science
From Atomistic Models to Machine Learning: Predictive Design of Nanocarbons under Extreme Conditions
Xiaoli Yan, Millicent A. Firestone, Murat Keceli et al. (+2 more)
The formation of technologically valuable nanocarbon structures under extreme conditions, such as those produced during high-explosive detonations, remains poorly understood but holds significant potential for the development of controlled synthesis pathways. While detonation shockwaves provide the HPHT environment required for nanodiamond formation, subsequent cooling and decompression dictate whether the diamond phase is preserved or transformed into other nanocarbon structures. Here, we employ GPU-accelerated ReaxFF simulations to investigate the graphitization and structural remodeling of detonation nanodiamond under nonlinear quench and pressure-release conditions. We further investigate how the initial nanodiamond morphology influences the resulting transformation products.
Evolution of nanostructure, allotrope, carbon hybridization, and ring statistics are tracked. Rapid cooling combined with slow decompression optimizes cubic diamond retention, whereas slow cooling with rapid pressure release promotes surface-to-core graphitization, producing concentric sp2 layers and hollowed inner shells. Octahedral nanodiamonds evolve into carbon nano-onions, initially forming bucky diamonds that progressively transform into full sp2 structures, while hexagonal prisms preferentially form parallel-stacked graphite layers resembling carbon dots. Lonsdaleite emerges as an interfacial phase, suggesting potential reversibility in the shock-induced graphite-to-diamond transformation pathway transformation route. To extend predictive capabilities, we trained MLP regressors on over 10^5 node-hours of simulations. The model reliably predicts the number of graphitized layers from T-P trajectories with R^2 exceeding 0.90. Collectively, morphological control combined with optimized quench-decompression conditions promote the selective synthesis of nanocarbon allotropes.
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All authors Xiaoli Yan, Millicent A. Firestone, Murat Keceli, Santanu Chaudhuri, Eliu Huerta
Materials Science · Cross-listed from cond-mat.soft
Synthesis, Solvent-dependent Self-Assembly and Partial Oxidation of Ultrathin Cerium Fluoride Nanoplatelets
Chiara Moretti, Damien Alloyeau, Benjamin Aymoz et al. (+5 more)
Two-dimensional colloidal nanoplatelets (NPLs) with atomically defined thickness exhibit unique physical properties, yet understanding their formation mechanism and assembly remains essential for tuning their collective behavior. We report an optimized synthesis of triangular cerium-based NPLs with narrow size and shape distributions via thermal decomposition of cerium trifluoroacetate. Combining X-ray diffraction, XPS, and high-resolution STEM, we show that the expected CeF3 NPL structure undergoes partial oxidation, yielding an oxyfluoride composition CeOxFy. Beyond their composition, we investigate how these oleic acid-capped NPLs organize in solution and at interfaces. The choice of solvent governs both the solution-phase organization and the resulting superstructures formed upon evaporation at the
liquid–air interface. In solvents that promote face-to-face stacking in solution, evaporation produces films organized into columnar assemblies tens of micrometers long, with the NPL planes oriented perpendicular to the interface. In contrast, solvents in which NPLs remain individually dispersed yield extended hexagonally ordered superlattices with edge-to-edge stacking spanning several micrometers, where the NPLs lie parallel to the interface in an edge-to-edge arrangement. These results highlight that solvent-mediated interactions and pre-existing organization in solution are decisive factors in determining the outcome of evaporative self-assembly of colloidal nanocrystals.
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All authors Chiara Moretti, Damien Alloyeau, Benjamin Aymoz, Laurent Lermusiaux, Rodolphe Valleix, Benoit Mahler, Marianne Impéror-Clerc, Benjamin Abécassis
Materials Science
Long photoexcited carrier lifetime in a stable and earth-abundant zinc polyphosphide
Zhenkun Yuan, Genevieve Amobi, Shaham Quadir et al. (+16 more)
Halide perovskites have revolutionized optoelectronics by demonstrating that long carrier lifetime can be achieved in materials processed in relatively uncontrolled environments, whereas conventional inorganic
semiconductors typically suffer from short carrier lifetime unless very carefully prepared and postprocessed. Here, we report the discovery of exceptionally long photoexcited carrier lifetime in monoclinic ZnP2, effectively bridging the carrier lifetime gap between direct-gap inorganic
semiconductors and halide perovskites. Through computational screening, ZnP2 is identified as a long carrier lifetime
semiconductor characterized by an unconventional polyphosphide bonding, combining covalently bonded phosphorus chains and polar-covalent Zn-P tetrahedra. Experimentally, ZnP2
crystals synthesized from low-purity precursors exhibit bright band-to-band photoluminescence at 1.49 eV and carrier lifetimes of up to 1 $\mu$s. Further analysis reveals that the polyphosphide bonding of ZnP2 suppresses the formation of deep intrinsic defects, making it defect resistant. Combined with its remarkable environmental stability, ZnP2 presents a highly promising material for
solar absorbers and light emitters. Our work illustrates that underexplored inorganic materials spaces with unusual chemical bonding hold great promise for discovering novel optoelectronic materials.
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All authors Zhenkun Yuan, Genevieve Amobi, Shaham Quadir, Smitakshi Goswami, Guillermo L. Esparza, Gideon Kassa, Gayatri Viswanathan, Joseph T. Race, Muhammad R. Hasan, Jack R. Palmer, Sita Dugu, Yagmur Coban, Andriy Zakutayev, Obadiah G. Reid, David P. Fenning, Kirill Kovnir, Sage R. Bauers, Jifeng Liu, Geoffroy Hautier
Materials Science · Cross-listed from physics.optics
Direct observation of ultrafast defect-bound and free exciton dynamics in defect-engineered WS$_2$ monolayers
Tae Gwan Park, Xufan Li, Kyungnam Kang et al. (+7 more)
Defects in two-dimensional transition metal dichalcogenides (TMDCs) broadly affect their optical and electronic properties. Directly capturing the ultrafast processes of
exciton trapping and defect-bound
exciton formation is crucial for understanding and advancing defect-mediated optoelectronics and
quantum technologies. However, the weak transient optical absorption of defect-bound
excitons has limited their experimental observation to date. Here, we report the direct observation of the ultrafast dynamics of defect-bound
excitons in monolayer WS$_2$
crystals with a high density of mono-sulfur vacancies (V$_S$) and W-site defect complexes (S$_W$V$_S$) resulting from synthesis by alkali metal halide-assisted chemical vapor deposition. The dynamics of
excitons bound to these defects, along with their coherent interactions with free
excitons, are elucidated using ultrafast optical spectroscopy. Using above band-edge photoexcitation, we find that both free and defect-bound
excitons simultaneously form within 300 fs from hot carrier relaxation. The defect-bound
excitons exhibit shorter lifetimes than free
excitons, leading to a population difference of the corresponding excitonic states and free
exciton trapping within a 1–100 ps window. Band-edge photoexcitation of free and defect-bound
exciton states reveals ultrafast interconversion within ~150 fs (comparable to our temporal resolution), indicating possible coherent coupling between these states. We further demonstrate efficient up-conversion of defect-bound
excitons to free
excitons with
photon energies up to ~300 meV below the free
exciton resonance. These findings provide insights into the ultrafast dynamics of defect-bound
excitons in TMDCs and their coupling with free
excitons, which are relevant to defect-engineered optoelectronic,
quantum photonic, and valleytronic applications.
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All authors Tae Gwan Park, Xufan Li, Kyungnam Kang, Austin Houston, Liam Collins, Gerd Duscher, David B. Geohegan, Christopher M. Rouleau, Kai Xiao, Alexander A. Puretzky
Materials Science
Polarization Dynamics in Ferroelectrics: Insights Enabled by Machine Learning Molecular Dynamics
Dongyu Bai, Ri He, Junxian Liu et al. (+1 more)
Ferroelectric materials with switchable spontaneous polarization underpin non-volatile
memories, transistors, sensors, and emerging neuromorphic chips. Their performance and stability are governed by polarization dynamics and domain kinetics, making a microscopic understanding of these processes and precise atomic level control of polarization domains key challenges for next-generation ferroelectric electronics. Due to the limitations of the characterization technology with atomic level in experiment, high precision atomic simulations become important. First principles calculations are inherently limited in accessible length and time scales, making it difficult to capture the complex features of dynamic processes. Machine learning molecular dynamics (MLMD) offers a compelling solution by encoding
quantum-mechanical accuracy into force fields, thereby enabling large scale dynamic simulations with near first-principles fidelity. This Perspective highlights the advantages of MLMD for simulating polarization switching, domain nucleation and migration, topological polar textures and
curvature-driven ferroelectric phenomena, while providing a systematic overview of recent progress in these areas. We further discuss methodological challenges that limit predictive capability, including long range electrostatics, coupled
lattice-
spin degrees of freedom in multiferroics, and data efficient pre-training of large atomistic models. Corresponding advances in long range aware force fields,
spin dependent machine learning models, and large scale pretraining are expected to move MLMD toward a genuinely predictive framework for the design of ferroelectric and multiferroic materials.
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All authors Dongyu Bai, Ri He, Junxian Liu, Liangzhi Kou
Materials Science · Cross-listed from cond-mat.str-el
Angle-Resolved Berry Curvature via Nonlinear Hall Effect of Ballistic Electrons
Louis Primeau, Qiong Ma and Yang Zhang
Berry
curvature fundamentally dictates the topological ground state, anomalous transport and optical properties of
quantum materials. However, directly mapping its momentum-space distribution in real materials remains an outstanding experimental challenge. Here, we present an inverse method for reconstructing the abelian Berry
curvature of a single band using angle-resolved measurements of the transverse conductance. Our inversion relies on a
symmetry-constrained statistical model with two hyperparameters that can be inferred directly from the nonlinear
Hall conductance, yielding a parameter-free inversion method. We demonstrate the feasibility of our method using simulated measurements of tight-binding models of WSe$_2$ and $ABC$-stacked trilayer
graphene.
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Materials Science · Cross-listed from cond-mat.supr-con
Quantum-Material Josephson Junctions: Unconventional Barriers, Emerging Functionality
Kathryn A. Pitton, Michiel P. Dubbelman, Trent M. Kyrk et al. (+5 more)
Josephson junctions translate
quantum phase coherence into an electrical response and underpin superconducting sensors and
quantum circuits. In conventional junctions, the barrier acts primarily as a passive weak link, however, when the barrier is a
quantum material with its own internal degrees of freedom like magnetism, strong correlations, or switchable polarization, the Josephson effect becomes a sensitive probe of
symmetry and many-body physics in the interlayer. Here we review progress in
quantum-material Josephson junctions, (QMJJ) focusing on three rapidly advancing barrier families: 1.
magnetic barriers, where exchange, noncollinearity, and
spin-active scattering enable 0-{\pi}-{\phi} ground states, singlet-triplet conversion, and nonreciprocal transport, 2. correlated barriers, where proximity effects acquire many-body character and recent van der Waals Kagome Mott interlayers exhibit field-free Josephson diode behavior, and 3. ferroelectric and multiferroic barriers, where nonvolatile polarization provides an internal control knob and can produce superconducting
memory and memristive dynamics.
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All authors Kathryn A. Pitton, Michiel P. Dubbelman, Trent M. Kyrk, Houssam El Mrabet Haje, Yaozu Tang, Roald J.H. van der Kolk, Yaroslav M. Blanter, Mazhar N Ali
Materials Science
Mechanistic Insights into Enhanced Alkaline Oxygen Evolution on Zn-Al Alloy Electrodes
Abdul Ahad Mamun, Rokon Uddin Mahmud, Shahin Aziz et al. (+3 more)
Electrochemical water electrolysis, which produces clean energy carriers to mitigate carbon emissions, lacks suitable, low-cost electrodes for efficient oxygen
evolution reaction (OER) in alkaline water splitting. To address this challenge, we developed Zn-Al
alloy electrodes with varying Al contents up to 20 wt.% via powder metallurgy method and conducted electrochemical measurements of the OER in alkaline solution to investigate their catalytic performance. We also performed first-principles calculations to examine their thermodynamic phase stability and electronic structures. Both theoretical and experimental results indicated that incorporating $\geq 20$ wt.% Al into Zn led to thermodynamic phase instability and secondary-phase segregation in Al-rich regions, limiting reaction kinetics and reducing catalytic efficiency. Although the Al content of 5 wt.% into Zn exhibited favorable thermodynamic and electronic characteristics, but its electrochemical performance was inefficient and poor due to inadequate reaction active sites on the surface. In contrast, the 10 wt.% and 15 wt.% Al into Zn showed approximately three- and two-fold increases in anodic exchange current density relative to pure Zn, respectively. Additionally, the anodic overpotential losses ($\eta_{0,a}$) measured at a current density of 12 mAcm$^{-2}$ were 0.240 V for Zn$_{0.9}$Al$_{0.1}$ and 0.5603 V for Zn$_{0.85}$Al$_{0.15}$, significantly lower than that of pure Zn ($\eta_{0,a} = 1.086$ V). While Zn$_{0.9}$Al$_{0.1}$ and Zn$_{0.85}$Al$_{0.15}$ showed similar charge transfer resistance ($R_{\rm CT}$), Zn$_{0.9}$Al$_{0.1}$ demonstrated superior reaction kinetics and lower $\eta_{0,a}$ across all samples tested. Furthermore, the improved kinetics and reduced overpotential of the Zn-Al
alloys favorably compare with those of other transition-metal-based catalysts, including Fe-Co-Ni-Mo
alloys and Fe-doped CuO.
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All authors Abdul Ahad Mamun, Rokon Uddin Mahmud, Shahin Aziz, Muhammad Shahriar Bashar, Ahmed Sharif, Muhammad Anisuzzaman Talukder
Materials Science
Substrate-controlled nucleation and growth kinetics in ultrathin Bi$_2$Te$_3$ films
Damian Brzozowski, Sander R. Hønnås, Egil Y. Tokle et al. (+2 more)
Metal chalcogenides are promising layered topological materials, yet their electronic performance is often limited by parasitic bulk conduction arising from defects that introduce excess carriers and shift the
Fermi level out of the topological regime. Controlling early-stage growth and defect formation is therefore essential for suppressing bulk transport and enhancing surface-state conduction. Here we investigate ultrathin Bi2Te3 films grown by pulsed
laser deposition on substrates spanning van der Waals,
lattice-matched, and amorphous regimes to determine how substrate-dependent nucleation pathways influence defect formation and electronic transport. Phase-pure, c-axis-oriented Bi2Te3 forms on all substrates, but the growth morphology varies strongly. Layered growth with well-defined quintuple-layer terraces is governed primarily by substrate roughness rather than
lattice match: atomically smooth mica and step-terraced SrTiO3 yield continuous terraces, whereas rougher BaF2 and amorphous Si3N4 produce island-structured films. Between the two smooth substrates, the higher surface energy of SrTiO3 enhances adatom adsorption and nucleation density, promoting rapid vertical growth and early Te depletion. Transport measurements reveal n-type conduction with carrier densities of 10e19-10e20 cm-3. The highest carrier density occurs for films on SrTiO3, consistent with defect formation during high-density nucleation, whereas mobility correlates with structural coherence and terrace formation. Weak anti-localization signatures confirm phase-coherent transport in films on mica and SrTiO3. These results show that substrate roughness and nucleation density provide key levers for controlling defect formation and strengthening topological surface transport in Bi2Te3 thin films.
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All authors Damian Brzozowski, Sander R. Hønnås, Egil Y. Tokle, Jørgen A. Arnesen, Ingrid G. Hallsteinsen
Materials Science
Simulating the influence of stoichiometry on the spectral emissivity of Mo$_x$Si$_y$ thin films
Zahra Golsanamlou, Arseniy Baskakov, Robbert van de Kruijs et al. (+4 more)
In this work, we simulate the spectral emissivity of various stoichiometric
crystal phases of Mo$_x$Si$_y$ compounds using density functional perturbation theory. The dielectric function, including electronic and ionic contributions, is calculated for each phase. We use the bulk properties obtained to simulate the optical absorption spectrum originating from the compound in thin film ($\sim$20 nm) form. We find that most thin films of Mo$_x$Si$_y$ are metallic, however, our results indicate that their emissivity is not simply correlated with the Mo content. For hot metallic films at around 900 K, we predict a maximal emissivity between 5-10 nm thickness. Our results are in good qualitative agreement with experiments, confirming that the emissivity of hexagonal MoSi$_2$ is much lower than in the tetragonal phase. This is related to the small band gap (hexagonal MoSi$_2$) and low density of states at the
Fermi level (tetragonal MoSi$_2$). Furthermore, test calculations on defected MoSi$_2$ demonstrate that the infrared emissivity of MoSi$_2$ thin films can be substantially increased by introducing defects.
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All authors Zahra Golsanamlou, Arseniy Baskakov, Robbert van de Kruijs, Silvester Houweling, Giorgio Colombi, Marcelo Ackermann, Menno Bokdam
Materials Science · Cross-listed from cond-mat.str-el
Site-selective renormalization and competing magnetic instabilities in paramagnet Y$_{3}$Cu$_{2}$Sb$_{3}$O$_{14}$
Yanpeng Zhou and Gang Li
Quantum spin liquids (QSLs) are exotic phases of matter characterized by long-range
entanglement and the absence of
magnetic order even at zero temperature. Here, we present a comprehensive theoretical study of the frustrated magnet Y$_3$Cu$_2$Sb$_3$O$_{14}$ to elucidate its electronic and
magnetic properties. We uncover completely opposite
crystal-field splittings of the two inequivalent Cu sites owing to their fundamentally distinct oxygen coordination - trigonal distorted octahedral CuO$_6$ and axially compressed CuO$_8$. This inversion places the unpaired hole in the $d_{z^2}$ orbital at the Cu-2 site, while Cu-1 maintains conventional $d_{x^2-y^2}/d_{xy}$ character, which results in a selective band-renormalization of orbitals from the two Cu ions. We further find multiple
magnetic instabilities competing with nearly equal strength in this system: the
spin susceptibility lacks dominant peaks, and the leading
eigenvalues approach unity simultaneously across all wavevectors with increasing interactions. This competitive interplay, originating from the distinct local environments and
geometric frustration on the triangular
lattice, agrees well with the absence of long-range
magnetic order in experiment. Our results support Y$_3$Cu$_2$Sb$_3$O$_{14}$ as a promising QSL candidate where the unique combination of disparate
crystal-field environments, strong correlations, and competing exchange interactions conspire to stabilize an exotic
quantum ground state.
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Materials Science · Cross-listed from cond-mat.supr-con
Reaching Quantum Critical Point by Adding Non-magnetic Disorder in Single Crystals of Superconductor $(\text{Ca}_x\text{Sr}_{1-x})_3\text{Rh}_4\text{Sn}_{13}$
Elizabeth H. Krenkel, Makariy A. Tanatar, Romain Grasset et al. (+5 more)
The Remeika series
superconductor, $(\text{Ca}_x\text{Sr}_{1-x})_3\text{Rh}_4\text{Sn}_{13}$, shows a rare nonmagnetic
quantum critical point (QCP) associated with the continuous charge-density wave (CDW) and structural transition under the “dome” of superconductivity achieved by tuning composition and applying pressure. Here we use a nonmagnetic point-like disorder induced by 2.5 MeV electron irradiation to suppress the CDW and drive the system to and even beyond the QCP. This conclusion is based on a clear
evolution of temperature-dependent resistivity, $\rho\left(T\right)$, from the
Fermi liquid to the non-
Fermi liquid regime with increasing amount of disorder. Starting on the CDW side, below the suggested QCP concentration of $x_c=0.9$, added disorder resulted in a progressively larger linear term and a reduced quadratic term in $\rho\left(T\right)$. Nearly perfect $T-$linear dependence is observed at the dose at which long-range CDW order is suppressed to $T=$0, consistent with the expectations. We refine the QCP location in this system and place it in the interval between $x=$0.75 and 0.85. Our results strongly support the concept that the disorder can tune the system to the
quantum critical regime and even beyond. It follows from the argument by Imry and Ma that any ordered phase is unstable toward quenched disorder. Introduced in a controlled way, this disorder becomes a novel non-thermal tuning parameter likely applicable to a variety of different systems.
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All authors Elizabeth H. Krenkel, Makariy A. Tanatar, Romain Grasset, Marcin Kończykowski, Shuzhang Chen, Cedomir Petrovic, Alex Levchenko, Ruslan Prozorov
Materials Science · Cross-listed from cond-mat.mes-hall
Magneto-rotation coupling dominates surface acoustic wave driven ferromagnetic resonance in the longitudinal geometry
Gyuyoung Park, OukJae Lee and Jintao Shuai
We present a
phonon-
magnon extension for the mumax+ micromagnetic framework that implements three surface acoustic wave (SAW) coupling mechanisms: magnetoelastic strain coupling, magneto-rotation coupling arising from the antisymmetric displacement gradient, and
spin-rotation (Barnett) coupling from the
lattice angular velocity. Six
benchmark simulations validate the implementation through SAW-driven domain-wall motion, magnetization switching, magneto-rotation and Barnett field validation, nonreciprocal SAW-
magnon absorption from Rayleigh-wave chirality, and spatially resolved coupling in a standing SAW cavity. For the longitudinal geometry (m_0 parallel to k_SAW), we show that the magnetoelastic coupling produces zero transverse torque despite generating a 50 times larger effective field; the magneto-rotation channel provides the sole driving mechanism. The crossover angle below which MR dominates is theta_c approximately 1.1 degrees for YIG parameters. Treating the magneto-rotation coupling constant K_mr as a tunable parameter, we map out the cooperativity phase diagram and show that MR alone can achieve strong coupling (C = 257 for K_mr = 1 MJ/m^3) with an avoided-crossing splitting of 13.6 MHz.
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Materials Science · Cross-listed from cond-mat.supr-con
Electron-Hole Scattering Dichotomy and Anisotropic Warping in Quasi-Two-Dimensional Fermi Surfaces of UTe2
Motoi Kimata, Jun Ishizuka, Freya Husstedt et al. (+13 more)
We present a combined experimental and theoretical study of the detailed
Fermi-surface (FS) geometry of UTe2, a heavy-
fermion superconductor that has recently attracted considerable
attention as a promising candidate for
spin-triplet pairing. Using angle-dependent magnetoresistance oscillations, a bulk- and low-energy-sensitive transport probe for quasi-two-dimensional (Q2D) electronic structures, we directly determine the in-plane FS geometry. We found that the Q2D FS exhibits a rectangular cross-sectional shape with strongly anisotropic warping, originating from the hybridization of two orthogonal quasi-one-dimensional bands. Through a quantitative comparison between experiment and theoretical calculations, we further reveal a large electron-hole scattering dichotomy: the quasiparticle lifetime on the electron FS is substantially shorter than that on the hole FS. This dichotomy is naturally explained by anisotropic, low-dimensional
antiferromagnetic fluctuations, which selectively enhance scattering on the electron FS. This suggests a dominant role of the electron pockets for the emergence of superconductivity. Our results clarify a direct relation between FS geometry,
magnetic fluctuations, and momentum-dependent quasiparticle lifetimes, and thus providing a crucial basis for the microscopic understanding of pairing mechanism, and impose stringent constraints on the gap
symmetry of
spin-triplet superconductivity in UTe2.
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All authors Motoi Kimata, Jun Ishizuka, Freya Husstedt, Yusei Shimizu, Ai Nakamura, Dexin Li, Yoshiya Homma, Atsushi Miyake, Yoshinori Haga, Hironori Sakai, Yoshifumi Tokiwa, Shinsaku Kambe, Yo Tokunaga, Dai Aoki, Toni Helm, Youichi Yanase
Materials Science · Cross-listed from physics.chem-ph
In-phase current and temperature oscillations reduce PEM fuel cell resistivity: A modeling study
Andrei Kulikovsky
We have developed a non-isothermal analytical model for the impedance of the cathode catalyst layer (CCL) in a PEM fuel
cell. In-phase harmonic perturbations to the current density and temperature reduce the impedance and the static polarisation resistivity of the CCL due to lowering
proton transport losses. A special selection of the current and temperature perturbation amplitudes allows for complete elimination of these losses.
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Materials Science
Chiral-Induced Spin Selectivity Effect in a 1 nm Thin 1,1'-Binaphthyl-2,2'-diyl Hydrogenphosphate Self-Assembled Monolayer on Nickel Oxide
Abin Nas Nalakath, Christian Pfeiffer, Anu Gupta et al. (+6 more)
The
chiral-induced
spin selectivity (CISS) effect describes an observed correlation between the orientation of an electron
spin transported or transferred through a molecule and that molecule's chirality. Suitable molecules are usually arranged as self-assembled monolayers (SAMs), and the primary CISS systems are based on multiple nanometer-long biomolecules exhibiting helical chirality. Aside from these typically thiolate-anchored molecules, phosphonic and phosphoric acid SAMs may well become significant for those CISS applications that require a more robust molecular coupling to metal
oxide surfaces. In this work, we report on our studies, employing the aromatic, low-molecular-mass, axially
chiral organophosphoric acid derivative 1,1'-binaphthyl-2,2'-diyl hydrogenphosphate (BNP). Grown as a roughly 1 nm thin SAM on top of a NiOx/Ni substrate, a strong circular dichroism signal indicates that the thin films preserved chirality. The CISS response exhibits a high magnetoresistance with a
spin polarization of 50-80% when measured using
magnetic-conductive atomic force microscopy. For biases above 0.5 V, the magnetoresistance curves could be well fitted to the Fowler-Nordheim (FN) tunneling model. Using a minimal FN model, we determined that, depending on the magnetization direction and the handedness of the molecules, electrons of a certain
spin direction face an effective tunneling barrier at high bias, which is either 80 % higher or 40 % lower compared to the barrier for electrons of the opposite
spin direction. Due to the small size of the molecules, their compatibility with
oxide materials, and their commercial availability, they are excellent candidates for the realization of novel (nanoscale) organic spintronic devices.
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All authors Abin Nas Nalakath, Christian Pfeiffer, Anu Gupta, Franziska Schölzel, Michael Zharnikov, Georgeta Salvan, Ron Naaman, Marc Tornow, Peer Kirsch
Materials Science
Polaron-mediated anisotropic exchange in 2D magnets
Johanna P. Carbone, Jakob Baumsteiger and Cesare Franchini
Two-dimensional (2D) magnets offer a rich platform for exploring emergent
spin phenomena due to their unique and diverse
magnetic properties. Beyond intrinsic magnetism, external manipulation$\unicode{x2013}$such as defect engineering, molecular adsorption, or charge doping$\unicode{x2013}$offers powerful routes to control their
magnetic behavior. In this work, we demonstrate that localized electron polarons provide an effective means to modulate magnetism in 2D magnets. Using first-principles calculations, we investigate polaron formation in monolayer MnPS$_3$ and compute the resulting changes in
magnetic exchange interactions. Our results reveal that polarons can locally break
magnetic symmetry and induce anisotropic exchange couplings, highlighting a novel mechanism for tuning
magnetic textures. This insight opens promising pathways for designing atomic-scale control of magnetism, with potential impact on spintronic technologies.
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Materials Science
Sub-angstrom many-body localization driven by phononic flat bands in real quantum materials
Yingpeng Qi, Jianmin Yang, Zhihui Zhou et al. (+10 more)
Defects, fluctuations, degenerate states and correlated interactions facilitate the emergence of exotic properties in condensed matter systems while also inducing atomic-scale local correlated structures that deviate from the average long-range order. Establishing the structure-property relationship from the perspective of these atomic-scale local correlated structures remains ambiguous and controversial due to the lack of direct methods for identifying such local correlated structures. In this work, based on the photoexcited ultrafast structural response, we propose a Bragg scattering phase breaking regime to identify sub-angstrom local correlated structures in
quantum materials. With this regime, we unambiguously identify the many-body-interaction driven local correlated structures in the low temperature ground state of AgCrSe2, characterized by static off-center displacements of Ag atoms ranging from 0 to 0.5 angstrom. The competition between Ag-Ag Coulomb correlations and potential wells induced by CrSe2 layers, leading to phononic flat bands and driving the system into a many body localization (MBL) regime. As temperature rising, these static local correlated structures transform to a dynamic state where the thermal fluctuations overwhelm the multiple localized states. These distinctive local correlated structures constitute the first experimental observation of MBL with
vortex-like topological characteristic in a real material system. Emergent vibrational modes arising from MBL have been confirmed and show excellent agreement with inelastic
neutron scattering experiments. Our work not only offers a universal approach to characterize sub-angstrom local correlated structures across a wide range of
quantum materials but also deepens our understanding of the fundamental mechanism behind exotic properties from the perspective of atomic-scale local correlated structures.
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All authors Yingpeng Qi, Jianmin Yang, Zhihui Zhou, Qing Xu, Yang Lv, Xiao Zou, Tao Jiang, Pengfei Zhu, Dongxue Chen, Zhenrong Sun, Lin Xie, Dao Xiang, Jiaqing He
Materials Science
Interface-dependent Phase Transitions and Ultrafast Hydrogen Superionic Diffusion of H2O Ice
Pengfei Hou, Yumiao Tian, Zifeng Liu et al. (+5 more)
High-pressure experiments using diamond anvils have revealed novel properties and phase behavior of H2O under extreme conditions. When contained in diamond-anvil
cells, the H2O samples are usually in direct contact with the diamond anvil. However, the extent to which this interface affects measured pressure-induced properties and behavior, including coexistence lines of ice phases, remains unknown. Combining artificial neural network methods and active learning schemes with large-scale molecular dynamics simulations, we elucidate the interfacial effects on various properties of high-pressure ice phases, including superionic states, solid-solid phase transitions, and melting. The results reveal that the presence of this interface can significantly lower the hydrogen superionic transition temperature. Remarkably, the interface can also induce a spontaneous transition from bcc- to fcc-based ice following the inverse Bain mechanism. Further, we redefined a stability field of bcc and fcc ice below the melting line and predicted the existence of fcc ice at much lower pressures than previously thought. More broadly, the results emphasize the importance of interface effects in understanding a wide range of phenomena reported in experimental studies of ice under pressure, including inconsistencies between theoretical and experimental results of this fundamental system.
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All authors Pengfei Hou, Yumiao Tian, Zifeng Liu, Junwen Duan, Hanyu Liu, Xing Meng, Russell J. Hemley, Yanming Ma
Materials Science
Hydrogen uptake and hydride formation in Al$_x$CoCrFeNi high-entropy alloys: First-principles, universal-potential, and experimental study
Fritz Körmann, Yuji Ikeda, Konstantin Glazyrin et al. (+9 more)
Hydrogen uptake in complex multicomponent
alloys, including high-
entropy alloys (HEAs), governs both hydrogen storage capacity and resistance to hydrogen-induced degradation. We combine high-pressure experiments, density-functional theory (DFT), and a GRACE universal interatomic potential to investigate hydrogen absorption in Al$_{0.3}$CoCrFeNi and Al$_3$CoCrFeNi HEAs. In H$_2$ as a pressure-transmitting medium, the FCC Al$_{0.3}$CoCrFeNi
alloy forms hydrides at ambient temperature above 3 GPa, whereas the Al-rich B2 Al$_3$CoCrFeNi
alloy shows no evidence of hydride formation even upon heating at pressures up to 50 GPa. Experiments and calculations show that aluminum suppresses hydrogen uptake by increasing solution energies and destabilizing interstitial sites. The universal potential, employed in the calculations and pretrained on large DFT databases, closely reproduces DFT energetics and demonstrates transferability from the dilute limit to the hydride-forming regime. Simulations further disentangle the roles of local ordering, volume changes, composition, and
crystal structure. Overall, our results indicate that hydrogen solubility in Al-containing HEAs is governed primarily by composition, with Al-driven B2 ordering as a strong secondary effect.
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All authors Fritz Körmann, Yuji Ikeda, Konstantin Glazyrin, Maxim Bykov, Kristina Spektor, Shrikant Bhat, Nikita Y. Gugin, Anton Bochkarev, Yury Lysogorskiy, Blazej Grabowski, Kirill V. Yusenko, Ralf Drautz