Materials Science
Operando Surface Probe Microscopy Reveals Electrochemical Origins of Reliability Variability in Hafnia Ferroelectrics
Anudeep Tullibilli, Kartick Biswas, Shubham Kumar Parate et al. (+1 more)
Device-to-device and sample-to-sample variability remains a major obstacle to the reliable implementation of hafnia-based ferroelectrics, even in nominally identical structures fabricated under similar processing conditions. This highlights the need for operando diagnostic probes that provide process-relevant feedback beyond conventional structural phase analysis. Here, we demonstrate that operando nanoscale surface measurements serve as sensitive probe of the local electrochemical processes governing reliability in hafnia ferroelectric devices. Using epitaxial rhombohedral Y:HfO2 films grown on La0.67Sr0.33MnO3 (LSMO)-buffered SrTiO3 as a model system, we combine operando atomic force microscopy, conductive AFM, piezoresponse force microscopy, and correlative STEM-EELS to directly link surface
evolution with interfacial electrochemistry. Devices exhibiting wake-up show a spatially uniform increase in surface height, arising from homogeneous oxidation of the LSMO electrode followed by oxygen migration into the ferroelectric layer during polarization switching. In contrast, leaky devices display pronounced surface roughening and blister formation, originating from spatially inhomogeneous oxidation states in the pristine LSMO electrode that promote competing oxygen
evolution reactions at the LSMO/Y:HfO2 interface. The accompanying electron generation produces leakage which is transient. Guided by these mechanistic insights, we introduce simple modifications to the processing conditions, without altering the optimized ferroelectric phase, that suppress the competing electrochemical pathways and reproducibly yield 100% ferroelectric devices. More broadly, this work establishes operando surface
evolution as a powerful nanoscale diagnostic of hidden electrochemical processes and provides a practical route for improving the reliability and reproducibility of hafnia-based ferroelectric devices.
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All authors Anudeep Tullibilli, Kartick Biswas, Shubham Kumar Parate, Pavan Nukala
Materials Science · Cross-listed from cond-mat.mes-hall
Nonlinear optical responses of semiconducting graphene nanoribbons: Strong constraint from a hidden symmetry
Jiawei Ruan, Weichen Tang, Yang-Hao Chan et al. (+3 more)
Nonlinear optical (NLO) responses are powerful tools for probing material structures, as they are highly sensitive to spatial
symmetries. For instance, it is well known that having inversion
symmetry forbids even-order NLO effects. Here, we show that nonspatial
symmetries can also significantly constrain NLO responses. In
graphene nanoribbons (GNRs) with bipartite-
lattice structures, we identify the approximate bipartite-
lattice particle-hole (BLPH)
symmetry strongly suppresses even-order NLO effects, even for systems with no inversion
symmetry. Importantly, we demonstrate that this approximate
symmetry enables the optical generation of nearly pure
spin shift currents in ferromagnetic GNRs, with the charge shift currents strongly suppressed. The
spin orientation of these photo-induced DC
spin currents can be easily tuned by an external
magnetic field, providing distinct advantages over previous schemes for generating pure
spin shift currents in antiferromagnetic systems. We illustrate our findings using a recently synthesized ferromagnetic Janus GNR. Our results underscore the significance of an overlooked
symmetry aspect of NLO responses and highlight
magnetic GNRs as promising candidates for spintronic devices.
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All authors Jiawei Ruan, Weichen Tang, Yang-Hao Chan, Chen Hu, Xiaoxun Gong, Steven G. Louie
Materials Science · Cross-listed from physics.ins-det
Quantitative Interleaved-Pulse Acquisition Extends the Range of Isotope-Ratio Measurements in ToF-SIMS
Anton V. Ievlev
Isotope ratios underpin tracer studies of transport in oxides, battery materials, and biological systems, yet time-of-flight secondary ion mass spectrometry (ToF-SIMS) struggles to quantify ratios whose members differ in intensity by orders of magnitude: a primary-ion pulse long enough to count the minor isotope precisely can saturate the major isotope, whereas a pulse short enough to keep the major isotope linear yields too few minor-isotope counts. We show that multi-pulse-width acquisition yields quantitative isotope ratios when a dose factor measured within each crater links the phases and each isotope is taken only from phases in which it remains linear; we call this quantitative reconstruction interleaved-pulse acquisition. Pulse widths are selected from measured transfer curves and peak shapes. On thermal SiO2, a tuned (6, 35) ns pair achieves the same per-layer precision as short-pulse acquisition with a 13-fold reduction in the number of analysis frames. On 18O-enriched WOx films, interleaving extends the quantifiable range at the low-fraction end by about 14-fold. Across isotope ratios spanning approximately 1:500 to 1:1, the interleaved reconstruction agrees with the corresponding linear reference measurements, showing no measurable bias introduced by interleaving, and natural-abundance ratios of oxygen, strontium and titanium are reproduced within several percent. The method requires no hardware additions and enables depth-resolved isotope-ratio measurements over a wide range within a single crater.
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Materials Science
Topological Hall Effect Induced by Chiral Spin Textures at the Ferroelectric/Ferromagnetic Interface
Jingkuan Xiao, Yaqing Han, Jianfeng Guo et al. (+25 more)
Chiral
spin textures, largely driven by the Dzyaloshinskii-Moriya interaction, offer significant potential for next-generation computing technologies due to their chirality and topological stability. Ferroelectric/ferromagnetic van der Waals
heterostructures are particularly appealing because they can combine interfacial inversion-
symmetry breaking and
spin-orbit coupling to promote interfacial Dzyaloshinskii-Moriya interaction, while switchable ferroelectric polarization provides a nonvolatile tuning knob. This study investigates interfacial chiral
spin textures in few-layer Fe$_3$GeTe$_2$/$\alpha$-In$_2$Se$_3$
heterostructures. Two groups of topological Hall signals are identified just below and above the coercive field, and thickness-dependent transport reveals a notable reduction in critical temperature with increasing Fe$_3$GeTe$_2$ layer thickness. Low-temperature
magnetic force microscopy images reveal two types of
magnetic bubbles with opposite
magnetic contrasts near the coercive field, each associated with distinct topological Hall signals. Together with atomistic
spin-dynamics simulations and first-principles calculations, these results support the formation of interfacial DMI-stabilized chiral
spin textures. Switching the ferroelectric polarization of the $\alpha$-In$_2$Se$_3$ layer further enables nonvolatile modulation of both anomalous and topological Hall effects. The resulting ferroelectric and
magnetic bistabilities generate four distinguishable Hall resistance states programmable by electric and
magnetic fields. These findings highlight the potential of van der Waals interfaces for advanced device applications.
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All authors Jingkuan Xiao, Yaqing Han, Jianfeng Guo, Renjun Du, Jiawei Jiang, Baoshan Cui, Runnong Zhou, Siqin Wang, Siqi Jiang, Fuzhuo Lian, Di Zhang, Guodong Ma, Jiabei Huang, Zhaochen Qu, Wanting Xu, Kenji Watanabe, Takashi Taniguchi, Alexander S. Mayorov, Jinsheng Wen, Haifeng Ding, Gong Chen, Ahmet Avsar, Hongxin Yang, Lihong Bao, Hong-Jun Gao, Shiyu Zhu, Lei Wang, Geliang Yu
Materials Science
Vapor phase growth and characterization of van der Waals BiSbTeSe platelets on semiconducting MoS2
M. Zhezhu, V. Torosyan, V. Mehrabyan et al. (+1 more)
Three dimensional topological
insulators of the tetradymite family, such as BiSbTeSe (BSTS), are attractive for spintronic and
quantum device applications because of their compensated, bulk-insulating character. Nanostructured BSTS platelets are promising for practical TI based devices. However, their growth often requires complex equipment, organometallic precursors, or electrically insulating substrates. Simple growth on technologically relevant semiconducting substrates remains largely unexplored. Here, we report the vapor phase growth of van der Waals BSTS platelets directly on semiconducting MoS2 using a presynthesized BiSbTe1.5Se1.5
crystal as the source material. The grown BSTS platelets exhibit thicknesses ranging from 4 nm to 246 nm, with an average lateral size of 1.4 mkm for individual platelets. Raman spectra of platelets, acquired in correlation with AFM thickness measurements, reveal contributions from both BSTS and the underlying MoS2 substrate. Among the characteristic BSTS modes, A21g mode shows the highest sensitivity to platelet thickness and local composition. EDS analysis reveals a systematic thickness dependence of the platelet composition, with an apparent crossover around 49 nm that coincides with a change in the thickness dependence of the low-wavenumber component of the E2g Raman band. This correlation suggests a composition-related origin of the Raman behavior, with the compositional variations tentatively attributed to the differential
volatility of the constituent elements during growth. These results demonstrate that MoS2 is a promising van der Waals platform for BSTS deposition and provide a structural and compositional baseline for future studies of BSTS-MoS2
heterostructures.
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All authors M. Zhezhu, V. Torosyan, V. Mehrabyan, A. Vasilev
Materials Science · Cross-listed from quant-ph
L-band single-photon generation from a cavity-coupled silicon C-center
Carolina Crosta, Kyu-Young Kim, Purbita Purkayastha et al. (+7 more)
Monolithic integration of single-
photon sources into silicon photonics offers a compelling solution for realizing scalable
quantum telecommunication architectures. Among the candidate silicon color centers, the C-center features a zero-
phonon emission in the telecom L-band, corresponding to the spectral window of minimum transmission loss in optical fibers. Despite this advantage, isolating single C-centers has remained an unrealized challenge in solid-state
quantum optics. In this work, we report the isolation of a single silicon C-center. We enhance the spontaneous emission rate of the zero-
phonon line by coupling the single emitter to a nanophotonic
crystal cavity, observing a fivefold reduction in the excited-state lifetime compared to bulk conditions, which corresponds to a Purcell factor lower bound of 33. Second-order autocorrelation measurements confirm single-
photon emission from the investigated defect, obtaining an optical purity of $g^{(2)}(0) = 0.23$ without background correction. Our results establish a native telecom L-band
quantum light source in silicon, laying the foundation for ultra-low-loss and long-distance
quantum applications.
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All authors Carolina Crosta, Kyu-Young Kim, Purbita Purkayastha, Abhijit Biswas, Jasvith Raj Basani, Amirehsan Alizadehherfati, Amirehsan Boreiri, Chang-Min Lee, Fabio Pezzoli, Edo Waks
Materials Science
Engineering Synaptic Dynamics in Ag-Modified TaO$_x$ Memristive Devices
R. Leal Martir, W. Quiñonez, A.J.T. van der Ree et al. (+4 more)
Engineering not only the magnitude but also the dynamics of synaptic weight updates is an important challenge for memristive neuromorphic hardware. Here, we show that Ag modification of TaO$_x$ memristors introduces an electrically selectable degree of freedom in synaptic depression through the interplay between Ag-related and oxygen-vacancy dynamics. Reference devices exhibit conventional bipolar switching, whereas Ag-modified devices display symmetric table-with-legs hysteresis loops, metastable intermediate states, and a strongly non-monotonic dependence of depression dynamics on programming amplitude. By varying only the pulse amplitude, the same device can be driven among three regimes: gradual sigmoidal depression, an abrupt update concentrated within a few pulses, and a broadly distributed
evolution extending over more than one hundred pulses. A minimal coupled-state model, in which a vacancy-related switching variable interacts with a slower Ag-related internal degree of freedom, reproduces this gradual–abrupt–gradual crossover using two individually monotonic field-activated processes. The functional impact is assessed in a memristor-based multilayer perceptron. For MNIST, the abrupt, sigmoidal, and slowly evolving responses yield accuracies of approximately 50%, 85%, and 88%, respectively, while the gradual regime reaches approximately 72% for Fashion-MNIST. These results show that coupling Ag-related and oxygen-vacancy dynamics can transform synaptic depression from a fixed device characteristic into an electrically programmable property.
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All authors R. Leal Martir, W. Quiñonez, A.J.T. van der Ree, M. H. Aguirre, G. Palasantzas, M. J. Sánchez, D. Rubi
Materials Science · Cross-listed from cs.LG
GLASS: Global Latent Aggregation with Slot-based Set Decoding for Scalable All-Atom Crystal Generation
Hendrik Kraß, Seyed Mohamad Moosavi and Mathias Niepert
Generative models for
crystals enable the discovery of novel structures, but scaling all-atom generation to larger systems such as metal–organic frameworks remains challenging. We connect this difficulty to the correspondence problem of particle-space generation. Even on a single fixed target set, index-free permutation-equivariant particle flows require substantially more training for reliable generation as set size and density increase, under both independent and optimal-transport couplings. To resolve this challenge, we introduce GLASS—Global Latent Aggregation with Slot-based Set Decoding, which encodes structures in a permutation-invariant global latent space and learns their distribution via flow matching. A learned-slot decoder constructs all atoms in parallel, removing atom-wise correspondence from generative transport. On MP20, GLASS is competitive with particle-space models, and flow training can reach the validity of the training data at every structure size. On a QMOF subset, GLASS generates MOFs with up to 150 atoms per unit
cell without conditioning on building blocks,
topology, or composition, and approaches the structural validity of the training data. On both
datasets, flow training exposes a validity–novelty tradeoff, and MOF novelty remains limited by autoencoder generalization on the available data. These results show that separating correspondence assignment from generative transport provides a simple route toward high-validity generation of larger atomistic systems.
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Materials Science · Cross-listed from cond-mat.str-el
Evolution of Magnetism in Ce$_4$Ge$_7$ under Magnetic Field and Pressure
Kaixin Ye, Qihe Yu, Yongjian Li et al. (+8 more)
We report the
magnetic and transport properties of single-crystalline Ce$_4$Ge$_7$, which crystallizes in a non-centrosymmetric orthorhombic structure (space group C222$_1$). It undergoes an antiferromagnetic transition at $T_N$ = 7.3 K. When a
magnetic field is applied along the $b$-axis, a metamagnetic transition occurs at 1.3 T (at 2 K). Correspondingly, this transition gives rise to an anomalous Hall effect, which is dominated by the intrinsic Karplus-Luttinger mechanism. Under hydrostatic pressure, $T_N$ of Ce$_4$Ge$_7$ initially increases slightly and is then gradually suppressed. For pressures above $P_c$ = 10.2 GPa, no
magnetic order is observed. The divergence of the $A$ coefficient, the maximum of the residual resistivity, and the non-Fermi
liquid behavior around $P_c$ indicate the possible existence of an antiferromagnetic
quantum critical point in Ce$_4$Ge$_7$.
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All authors Kaixin Ye, Qihe Yu, Yongjian Li, Yanan Zhang, Ye Chen, Rui Li, Lin Jiao, M. Smidman, Yongjun Zhang, Yu Liu, Huiqiu Yuan
Materials Science
Defect-controlled electrical and optical properties of CrN thin films: experiment and first-principles study
J. Bulíř, U. D. Wdowik, J. More-Chevalier et al. (+7 more)
Thin chromium nitride (CrN) films were deposited by RF magnetron sputtering in a reactive atmosphere of Ar-N$_2$ on fused silica and MgO (001) substrates at temperatures between 400 $^o$C and 800 $^o$C. The influence of nitrogen content and substrate temperature on structural, electrical, and optical properties was systematically investigated. The overstoichiometric CrN films exhibited a reduced resistivity below 6 m$\Omega \cdot$cm with stable p-type behavior, while increasing the substrate temperature above 600 $^o$C induced a transition to n-type conductivity. Spectroscopic ellipsometry in the UV-Vis-NIR and infrared spectral ranges revealed a strong dependence of the dielectric function and the absorption edge on film stoichiometry and deposition conditions. Structural characterization using X-ray diffraction and atomic force microscopy confirmed substrate-dependent crystallinity and grain growth. Density functional theory calculations showed that cation and anion vacancies strongly modify the electronic structure and optical response, explaining the experimentally observed conductivity transitions. The results demonstrate that the deposition parameters provide an effective means to tailor CrN thin films via defect engineering.
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All authors J. Bulíř, U. D. Wdowik, J. More-Chevalier, P. Hubík, E. de Prado, M. Vondráček, L. Fekete, M. Novotný, J. Lančok, D. Legut
Materials Science
Linear-Scaling Quantum Transport from Machine-Learning Density Functional Theory Hamiltonians
Bang Liu, Yang Zhong, Zhi-Xin Guo et al. (+2 more)
Quantum transport simulations that combine density functional theory (DFT) with the nonequilibrium Green's function formalism (DFT-NEGF) are important to modern technology, yet their unfavorable scaling has long confined predictive simulations to small, idealized systems far below the ten-thousand-atom scale of realistic devices. Here, we introduce HamGNN-NEGF, a linear-scaling framework with DFT-level fidelity. An E(3)-equivariant graph neural network trained on conventional DFT
Hamiltonians of small structures predicts
Hamiltonians for large devices, avoiding costly DFT-NEGF training data. The predicted
Hamiltonians are integrated with DFT-derived electrode self-energies, a nonorthogonal kernel
polynomial method for Fermi-level determination, and a recursive Green's function
algorithm, yielding a computational cost that scales linearly with device length at fixed cross section. Even for devices containing fewer than 500 atoms, HamGNN-NEGF achieves speedups exceeding three orders of magnitude over fully self-consistent DFT-NEGF, with the advantage increasing further with system size.
Benchmarks on pristine Pt-Si-Pt, doped Pt-Si:P-Pt, and Pt-molecule-Pt junctions demonstrate meV-level
Hamiltonian accuracy, faithful transmission spectra, and predictive simulations beyond 10,000 atoms. Eliminating transport self-consistency also enables hybrid functionals such as HSE06 without additional NEGF overhead, while a zero-bias
Hamiltonian approximation extends the framework to finite-bias transport in weakly nonlinear regimes. HamGNN-NEGF thus bridges first-principles accuracy and device-scale simulation, providing a practical route toward predictive modeling of realistic nanoelectronic and
quantum devices.
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All authors Bang Liu, Yang Zhong, Zhi-Xin Guo, Xin-Gao Gong, Hongjun Xiang
Materials Science
HyTopo A High-Performance Hierarchical Algorithm for Mapping the Structural Evolution and Transition Networks of Gas Hydrates
Zherui Chen, Shuquan Huang, Ke Xu et al. (+6 more)
Resolving the formation and dissociation mechanisms of hydrate requires identifying not only hydrate-like water, but also the specific cage
topologies by which disordered
liquid water reorganizes into, or escapes from, crystalline hydrate networks. Here we introduce HyTopo, a cage-
topology-centered analysis framework that combines a hydrate order parameter, hierarchical ring and cage recognition, and cage-transition network analysis. Based on local orientational correlations, HyTopo classifies water molecules into
liquid-like, precursor-like, hydrate-like, and ice-like environments, and uses this information to guide efficient topological searches for crystalline hydrate cages and defective intermediates. Applications to methane hydrate growth, homogeneous nucleation, and depressurization-induced dissociation reveal that hydrate
evolution is governed by heterogeneous and pathway-dependent cage dynamics. During hydrate growth, EA-WPU suppresses the overall proliferation of cage-like structures while altering the balance between defective cages and crystalline sI cages. During nucleation, incomplete cage motifs dominate the early pathway and provide a structural reservoir from which a small fraction of stable 512 and 51262 cages. Hydrate dissociation proceeds through interfacial collapse, bulk decomposition, and dissolved-gas exsolution, with cage lifetimes and transition pathways strongly dependent on cage
topology. These results show that HyTopo provides a physically interpretable and
topology-resolved route to connect local water ordering, cage formation, structural defects, and hydrate phase transitions in complex molecular simulations.
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All authors Zherui Chen, Shuquan Huang, Ke Xu, Zhanbo Li, Xinyu Song, Haijun Wang, Dingyuan Tang, Qingxia Liu, Yajun Deng
Materials Science
24-hr Solid-State Power Generation with Self-Adaptive Tunable Radiative Coatings
Ken Araki and Liping Wang
Day-night solid-state power generation is experimentally demonstrated with thermoelectric generators integrated with a tunable radiative coating, which switches between a selective solar absorber during daytime and a radiative cooler during nighttime by temperature without any external control. The self-adaptive radiative coating is carefully designed with thermochromic VO2 thin film on heavily doped silicon substrate along with a phase-shifting silicon spacer in between, whose physical mechanism is elucidated. The fabricated coating exhibits a high solar absorptivity of 0.90 and a low infrared emissivity of 0.23 during daytime, and a high emissivity of 0.85 at night, resulting in large emissivity change of 0.62 within the atmospheric transparency window upon metal-to-
insulator phase transition. From outdoor tests in a high
vacuum apparatus, the tunable radiative coating in 35-mm squared size achieves 1.64 W/m2 power generation around noon time from a stack of commercial thermoelectric modules of 15 mm squared, which is 32% more from that with a black absorber. At night, it produces 26 mW/m2 power, outperforming the black emitter by 63%. Even exposed the ambient with convective loss, the 2-inch-round tunable coating generates power of 0.48 W/m2 at noon time, 14% more than the black absorber of the same size. The tunable radiative coating covered thermoelectric modules produces open
circuit voltages from 433 mV to -62 mV in
vacuum and from 300 mV to -51 mV in ambient through 24-hr continuous outdoor tests.
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Materials Science · Cross-listed from cond-mat.mes-hall
Deep Learning GW Quasiparticle Hamiltonians for Many-Body Excited-State Electronic Structure at Scale
Xiaoxun Gong, Zechen Tang, Woochang Kim et al. (+4 more)
Accurate quasiparticle electronic structures are the foundation for understanding excited-state properties of materials and explaining optoelectronic,
quantum, and transport phenomena. First-principles GW calculations nevertheless remain computationally intensive for large or configurationally complex systems. Here we introduce DeepH-GW, a deep-learning framework that predicts an effective GW quasiparticle
Hamiltonian directly from atomic structure. Building on the local, equivariant message-passing architecture of DeepH, DeepH-GW is trained on high-fidelity plane-wave GW calculations through a real-space
Hamiltonian-reconstruction interface. This approach combines the systematic accuracy and broad chemical applicability of plane-wave methods with linear-scaling neural-network inference. Across the systems examined, DeepH-GW reproduces quasiparticle band structures with errors on the order of a few meV. Moreover, we show that, despite the intrinsic nonlocality of many-body interactions, DeepH-GW exhibits strong cross-scale transferability from relatively small training structures to substantially larger supercells. We demonstrate that the framework can accurately capture GW-level electron-
phonon band-gap renormalization through predictions in supercells with thermal displacements, illustrating the power of the approach. DeepH-GW therefore provides a practical route toward large-scale many-body simulations and foundation models for excited-state electronic structure.
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All authors Xiaoxun Gong, Zechen Tang, Woochang Kim, Yang Li, Wenhui Duan, Yong Xu, Steven G. Louie
Materials Science
Tuning the secondary electron yield and electronic conductivity of MgZnO multilayers synthesized by Atomic layer deposition
Mathieu Lafarie, Sarah Dadouch, Fréderic Miserque et al. (+4 more)
Secondary electron emission (SEE), arising from the interaction of energetic electrons with material surfaces, can induce deleterious effects in
vacuum radio-frequency (RF) systems, notably multipacting, thereby degrading performance and threatening device integrity. Despite extensive efforts, effective and widely adopted mitigation strategies remain limited. Here, we report an approach to simultaneously tailor SEE and electrical conductivity using nanometric multi-element multilayers deposited by atomic layer deposition (ALD). The design and fabrication of these
heterostructures are presented, and a range of films is systematically characterized to establish correlations between emission properties, electrical conductivity, chemical and structural features. We demonstrate that such
heterostructures enable combinations of total electron emission yield (TEEY) and conductivity unattainable in single-phase materials, including regimes combining high TEEY with relatively high conductivity and low TEEY with low conductivities. These results open new avenues for the rational design of functional surfaces for
vacuum electronic applications.
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All authors Mathieu Lafarie, Sarah Dadouch, Fréderic Miserque, Yunlin Zheng, Jocelyne Leroy, Mohamed Belhaj, Thomas Proslier
Materials Science
Orientation engineering is a universal strategy for ferroelectric trans-switching
Cameron Scott and Jorge Íñiguez-González
About two decades ago, “strain engineering” emerged as a powerful strategy to tune epitaxial thin films. Here we contend that ”orientation engineering” - that is, controlling the film's growth direction - constitutes a complementary design route that opens unprecedented opportunities and deserves greater
attention. Specifically, we show that orientation engineering can endow standard ferroelectric compounds with exotic and useful behaviors that may be difficult or impossible to obtain otherwise. Critically, we predict it readily enables ”trans-switching,” where polarization components switch perpendicularly to the applied electric field, paving the way for novel 3D device architectures. We also show that, by controlling the electric screening provided by electrodes in contact with the film, ferrielectric behavior can be obtained. Notably, one can even design an operational mode where the switching is, in effect, fully transversal to the applied field. Supported by phenomenological calculations for representative compounds LiNbO$_3$ and BaTiO$_3$, we thus propose orientation engineering as a powerful and general method to unlock unprecedented functionalities in common ferroelectrics.
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Materials Science · Cross-listed from cond-mat.str-el
Quantized Hyperfine Field at an Implanted $\mu^+$ Site in PrPb$_3$: Interplay between Localized $f$ Electrons and an Interstitial Charged Particle
T. U. Ito, W. Higemoto, K. Ohishi et al. (+6 more)
The local effect of an interstitial hydrogen-like particle on localized $f$ electrons was studied in PrPb$_3$ by means of $\mu^+$
spin rotation and relaxation. Spontaneous $\mu^+$
spin precession with harmonic frequencies was observed for the first time in $f$ electron compounds. We demonstrate that the signal is derived from a coupling between the $\mu^+$
spin and the hyperfine-enhanced nuclear
spin of nearest neighbor (nn) $^{141}$Pr with Ising-like anisotropy. The signal also suggests a marked suppression of
spin dynamics of the nn $^{141}$Pr in comparison with that of the bulk $^{141}$Pr. These facts strongly indicate modification of the $f$ electronic state due to the interstitial charged particle.
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All authors T. U. Ito, W. Higemoto, K. Ohishi, N. Nishida, R. H. Heffner, Y. Aoki, A. Amato, T. Onimaru, H. S. Suzuki
Materials Science
Evidence for Distributed Fault Energetics and Their Impact on Deformation in a Chemically Complex Alloy
Kaijun Yin, Jun-Ping Du, Peijun Yu et al. (+7 more)
Chemically complex
alloys feature intrinsically heterogeneous local chemical environments and, consequently, fluctuations in local fault energetics. However, experimentally quantifying their relationship remains challenging, leaving the role of this distributed energy landscape in deformation mechanisms incompletely resolved. Here, we develop a distribution based framework linking experimentally measured stacking fault widths to deformation relevant apparent fault energy, revealing a distributed local fault-energy landscape in CrCoNi. The framework reveals the stabilizing role of energy fluctuations and captures an upward shift in the apparent fault energetics, from negative values toward zero following heat treatment, which atomistic simulations associate with the emergence of L12 type chemical short-range order. Using one-dimensional kinetic Monte Carlo simulations, supported by electron microscopy observations, we further show that history-dependent changes in the local fault-energy landscape bias the competition among stacking faulting, nano-twinning and HCP transformation in CrCoNi. Our results provide an experimentally anchored, distribution-based framework for understanding deformation in chemically complex
alloys as it evolves within a distributed fault-energy landscape shaped by local chemical order.
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All authors Kaijun Yin, Jun-Ping Du, Peijun Yu, Rui Feng, Hanyu Hou, Haw-Wen Hsiao, Ke An, Peter K. Liaw, Shigenobu Ogata, Jian-Min Zuo
Materials Science
Synthesis and modification of thin NaSICON solid electrolytes using ion beams
Giovanni Ceccio, Jiri Vacik, Ivan Mastronardo et al. (+3 more)
Solid electrolytes (SEs) for sodium-based superionic conductors (NaSICON) were first introduced in 1976 and quickly recognized for their excellent ionic conductivity. While considerable effort has been made to develop thin electrolytes for all-solid-state batteries (ASSBs), only a few sodium-based SEs have been successfully fabricated as thin films. These thin films are particularly desirable for their reduced electrical resistance, which typically increases with the thickness of the SE. By reducing the thickness of the SEs to the nanometer scale, their ionic conductivity can be significantly enhanced. In this study, the NASICON composite was initially prepared in the form of pellets using the mixed oxide technique with a planetary ball mill and synthesized by the solid-state method at 1300 {\deg}C. The resulting pellets were used as sputtering targets in a low-energy ion facility to prepare continuous NASICON nanofilms. To explore the effect of ion implantation on the electrical properties of NASICON, the prepared films were bombarded with Ni ions at 1.1 MeV and varying fluences, using the Tandetron accelerator at the CANAM infrastructure (NPI Řež). The electrical properties of both the synthesized and implanted films were analyzed through electrochemical impedance spectroscopy (EIS). The results, describing the impact of irradiation on NASICON's properties, are presented here.
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All authors Giovanni Ceccio, Jiri Vacik, Ivan Mastronardo, Clausia D Urso, Eva Stepanovska, Romana Miksova
Materials Science
Fabrication framework for three-dimensional colloidal particles with decoupled geometry and material composition
Hamed Almohammadi, Gurminder K. Paink, Vasumathi Venkat et al. (+6 more)
Shape-programmable particles offer significant opportunities for microrobotic systems at the individual level and for hierarchical materials with emergent functionalities arising from collective particle behavior. However, fabricating shape-changing stimuli-responsive particles with complex three-dimensional geometries at colloidal length scales remains a major challenge. Here, we introduce a general fabrication framework that decouples particle geometry from material composition to produce free-standing three-dimensional colloidal particles with complex architectures. Our approach combines soft lithography, swelling-assisted extraction, and sacrificial adhesive transfer to fabricate particles with high
geometric fidelity. We establish a predictive framework that defines the accessible design space for increasingly complex particle geometries. We further extend our framework to fabricate high-aspect-ratio pillar arrays with intricate three-dimensional architectures at colloidal length scales. To demonstrate material versatility, we fabricate particles from both
liquid crystal elastomers and hydrogels. We show reversible shape-changing behavior of
liquid crystal elastomer particles with cylindrical and chiral shapes under thermal and optical stimuli. In suspension, these particles display collective optical dynamic behavior arising from coupling between changes in the programmed
liquid crystal organization within the particles and stimulus-induced
geometric reconfiguration of the particles. Collectively, this work establishes a versatile platform for geometry-programmable colloidal particles with emergent collective functionalities, providing a route toward materials and fluids with dynamically programmable properties.
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All authors Hamed Almohammadi, Gurminder K. Paink, Vasumathi Venkat, Jacopo Movilli, Atalaya Milan Wilborn, Haritosh Patel, Haichao Wu, David Weitz, Joanna Aizenberg
Materials Science
Polar-Domain Volume as a Unified Descriptor of Transport in Ionic Liquids
Ganesh K. Rajahmundry and Tarak K. Patra
Developing molecular scale structural descriptors that can quantitatively predict the macroscopic transport properties of ionic
liquids remains a longstanding question, owing to the complex interplay between molecular interactions, nanoscale organization, and collective ion dynamics. Here, we use all atom molecular dynamics simulations to establish quantitative structure property relationships between the
equilibrium microstructure and two key transport properties viscosity and ionic conductivity in a series of imidazolium based ILs with chemically distinct anions and varying alkyl chain lengths. While viscosity and ionic conductivity exhibit distinct dependencies on alkyl chain length and anion chemistry, these seemingly different trends largely collapse onto unified correlations when expressed in terms of the mean polar-domain volume. In particular, both transport properties exhibit systematic power-law scaling with the mean polar domain volume fraction, revealing a common structural origin underlying the variations in ion and momentum transport across chemically distinct ILs. These results establish polar-domain volume as a physically motivated molecular-scale descriptor and provide a general structure property framework for connecting nanoscale organization to macroscopic transport properties in ILs.
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Materials Science
Averaging in thermodynamic dislocation theory: general macroscopically uniform stress and strain states
Khanh Chau Le
The averaging procedure, developed for polycrystalline bars under axially symmetric tension or compression, is extended to arbitrary macroscopically uniform stress and strain states. Starting from the equal probability hypothesis for grain orientations, the mean resolved shear stress and the mean resolved elastic and plastic shear strains are defined as root-mean-square averages over all slip-system orientations. Two exact identities for isotropic orientation averages show that the mean resolved shear stress is proportional to the von Mises equivalent stress, and that the direction of macroscopic plastic flow, obtained from the hypothesis that the plastic slip rate on a system is proportional to the resolved shear stress acting on it, is the stress deviator. The result is an associated $J_2$ flow theory whose hardening law is not fitted but follows from the kinetics of thermally activated dislocation depinning and the
evolution equations for the dislocation density and the effective disorder temperature of thermodynamic dislocation theory, written as rates with respect to time so that arbitrary loading paths can be followed. For torsion the theory yields the torque–twist relation of bars and tubes without the classical reductions to a shear stress–strain curve. The parameters for copper are identified jointly from Hopkinson-bar tension, dynamic compression at room and elevated temperatures, and torque–twist records at several twist rates. One set of material parameters, consistent with the earlier compression-only identification, describes tension, compression and torsion from room temperature to $1173$\,K and from $10$ to $2300$\,s$^{-1}$ to $6$\,% rms over 142 data points; the tension–torsion discrepancy noted by Johnson and Cook is traced to the initial dislocation state of their torsion specimens.
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Materials Science · Cross-listed from cond-mat.mes-hall
Linear and nonlinear transport responses of topological nodal-line semimetals
L. E. Sosa-Arias and A. Martín-Ruiz
Topological nodal-line semimetals are three-dimensional
quantum materials characterized by band crossings that form closed loops in momentum space. In $\mathcal{PT}$-symmetric realizations, these nodal rings are stabilized in the absence of
spin-orbit coupling, giving rise to drumhead surface states and unconventional transport responses. In this work, we study charge transport across a nodal-line semimetal containing a finite electrostatic barrier, with both leads described by the same
equilibrium material. By solving the corresponding scattering problem, we show that the transmission across the barrier exhibits {Klein-tunneling behavior protected at normal incidence by the nodal
topology}, despite the extended nodal-line dispersion, which can be traced back to Berry-
curvature-induced momentum locking. Using the Landauer-Büttiker formalism, we derive general expressions for the linear and nonlinear conductances, including both longitudinal and Hall components, and evaluate them at zero and finite temperature. Our analytical and numerical results elucidate the dependence of the conductance on barrier height and width, as well as on a $\mathcal{PT}$-breaking mass term. We identify distinct transport regimes in which nonlinear contributions are strongly enhanced and transverse Hall currents emerge, providing clear transport signatures of nodal-line
topology and suggesting potential routes toward device applications.
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Materials Science · Cross-listed from cs.LG
A Digital Simulation Toolkit for Physics-Based Generation of Realistic Experimental Scanning Tunneling Microscopy Images
Huanhuan Zhao, Laxmi Bhurtel, Connor Vernachio et al. (+3 more)
Scanning Tunneling Microscopy (STM) is a widely used tool for characterizing surfaces of materials at the atomic scale, playing a crucial role in discoveries across condensed matter physics and materials science. Despite its extreme spatial resolution, STM is one of the most sensitive microscopy techniques and is highly prone to noise. While existing unsupervised denoising methods are very cheap to train, these are primarily focused on removing the noise with minimal recovery of key physical information. While supervised methods can offer superior performance, the major bottleneck is that a large amount of paired clean-noisy experimental images is required which are impractical to obtain. Thus, we developed a low-cost physics-driven digital toolkit to rapidly generate large volume of realistic STM images. Firstly, we simulate clean images from a chosen material system. Then, with prior knowledge of the physical characteristics of the artifacts and noise present in STM experiments, we formulate several artifact-noise functions such as Gaussian electronic noise, 1/f flicker noise, scan-line noise, background tilt and mechanical drift. These physically informed noise components are then added to the simulated clean images to generate realistic STM images. We demonstrated the capability of the proposed digital toolkit to generate AI-ready data for denoising images of the (111) surfaces of copper and lead, while preserving atoms, defects, and electron waves. We also validated the quality of the downstream image analysis of learning electron wave patterns induced by
quantum interference from Cu(111) images. Results show that the supervised models trained on digitally generated AI-ready data can more effectively denoise and learn electron wave patterns on Cu(111) images than benchmarked unsupervised approaches, indicating that the proposed toolkit facilitate scientific discovery.
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All authors Huanhuan Zhao, Laxmi Bhurtel, Connor Vernachio, Fahmy Paiziah, Wonhee Ko, Arpan Biswas
Materials Science · Cross-listed from cond-mat.mes-hall
Magnetic-field-activated transport from band geometry in gapped nodal-line semimetals
L. Medel Onofre, L. E. Sosa-Arias and A. Martín-Ruiz
We develop a nonperturbative semiclassical theory of magnetotransport in gapped nodal-line semimetals, retaining the full
magnetic-field dependence of Berry-
curvature and orbital-
magnetic-moment corrections. Starting from a minimal two-band model, we derive exact expressions for both the intrinsic Hall response and the dissipative Fermi-surface conductivity, valid to all orders in the
magnetic field within the semiclassical regime. We show that the orbital
magnetic moment reconstructs the geometrically active Fermi surface, breaking the azimuthal cancellation imposed by the nodal-line geometry and thereby activating an intrinsic Hall current that is absent at zero
magnetic field. The Hall response exhibits a pronounced nonmonotonic dependence on the chemical potential and a strongly nonlinear
magnetic-field
evolution, reflecting the redistribution of geometrically active states around the nodal ring. We further demonstrate that the Fermi-surface conductivities recover the conventional Drude behavior in the weak-field limit, while acquiring quadratic and ultimately nonperturbative
magnetic-field corrections together with a field-induced transport anisotropy that gives rise to a measurable planar Hall effect at intermediate fields. Both the intrinsic and dissipative responses are strongly enhanced when the Fermi level lies close to the nodal ring, where Berry
curvature and orbital
magnetic moment are largest. Our results identify
magnetic-field-activated
geometric transport as a characteristic signature of nodal-line semimetals and provide a unified framework for describing magnetotransport beyond perturbative
magnetic-field expansions, together with experimentally accessible signatures of orbital-
magnetic-moment physics.
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Materials Science · Cross-listed from cs.RO
A robust single-sensing-element tactile sensor for concurrent pressure and tackiness detection with real-time signal decoupling capability
Ying Yang, Mingwei Gu, Jia-Sen Xie et al. (+8 more)
Integrating tackiness sensation into the artificial skin of humanoid
robots significantly enhances their cognitive and operational capabilities. However existing tactile sensors face challenges in decoupling of the
multimodal signal and stability. Here we present a surface-soft tactile sensor that incorporates a Hall effect sensor and a soft
magnetic composite within a robust elastic framework. The sensor surface indents under pressure and bulges prominently when retracted from sticky surfaces dynamically altering the Hall sensor-magnet distance. This generates whole-process-traceable and baseline-separated signals enabling real-time differentiation between pressure and pull-off force. This single-sensing-element design facilitates bimodal sensing at the same contact spot while eliminate stress cross-talk enhancing both accuracy and sensitivity. The fusion of a robust framework and magneto-mechanical sensing mechanism equips the sensor with exceptional reliability and excellent signal baseline stability. This tactile sensor holds substantial potential for advancing robotic capabilities in evaluating adhesive properties monitoring rubber aging precisely handling lightweight objects and cognizing natural objects surface characteristics.
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All authors Ying Yang, Mingwei Gu, Jia-Sen Xie, Xingyu Ma, Yan-Na Lu, Lin Zheng, Jinhui Gu, Junshuai Chen, Yunjie Lu, Denys Makarov, Jin Ge
Materials Science
Frustrated Gd3+ Double Perovskites as High-Performance Magnetocaloric Materials for Sub-100 mK Adiabatic Demagnetization Refrigeration
Tim Treu, Marvin Klinger, Christian Heil et al. (+6 more)
Achieving temperatures below 100 mK is essential for advancing
quantum technologies and exploring fundamental
quantum phenomena. While paramagnetic salts have traditionally enabled adiabatic demagnetization refrigeration (ADR), their limitations have driven the search for more effective alternatives. In this work, we present Gd3+-based double perovskites, Ba2GdSbO6 and Sr2GdSbO6, as high-performance magnetocaloric materials. Starting ADR from 2 K and 5 T, these compounds reach 67 mK and 68 mK in small finite
magnetic fields, and 83 mK and 78 mK in zero field, respectively, which are the lowest reported ADR temperatures for Gd3+ magnets (S = 7/2) under these conditions. The frustrated geometry and the complex interplay of exchange and dipolar interactions suppress their antiferromagnetic ordering temperatures to 100 and 166 mK for Ba2GdSbO6 and 190 mK for Sr2GdSbO6, while maintaining an outstanding
entropy density of 189 mJ K-1 cm-3 and 201 mJ K-1 cm-3, respectively. Notably, Ba2GdSbO6 sustains sub-100 mK cooling even at finite fields of 0.5 T, making it particularly promising for practical ADR applications.
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All authors Tim Treu, Marvin Klinger, Christian Heil, Hans-Albrecht Krug von Nidda, Vinicius E. S. Frehse, Mamoun Hemmida, Anton Jesche, Alexander A. Tsirlin, Philipp Gegenwart
Materials Science
Enabling the Ambient Pressure Growth of ScB2 Crystals for AlGaN Power Electronics
Satya K. Kushwaha, Ahamed Raihan, Astrid D. Kengne et al. (+19 more)
Here we report the growth of single crystalline ScB2, an ultrahigh-temperature ceramic, at ambient pressure in a
laser-heated Optical Floating Zone via the travelling solvent method.
Crystals have been grown from both Sc-rich (55-65 at% Sc) and B-rich self-flux (80-83 at% B) at growth rates in the range of 0.2-2 mm/hr. The structure of grown
crystals is in good agreement with an AlB2-type layered hexagonal phase, space group P6/mmm, with
lattice constants a = 3.1423(2) Å\ (resp. 3.1502(3) Å) and c = 3.5084(3) Å\ (resp. 3.5041(3) Å) for
crystals grown under Sc-rich (resp. B-rich) conditions.
Crystals natively grow along the in-plane [100] direction. Electron backscattered diffraction shows that Sc-flux growth results in boules with multiple domains containing Sc inclusions, with the domains highly aligned. In contrast, B-flux boules are single domain after the initial nucleation region. Rocking-curve measurements of B-flux
crystals for the (h000) and (000l) reflections show single peaks, establishing that the
crystals are free from grain boundaries; the asymmetry in the scattered-intensity tails suggests the presence of point defects. Surface X-ray photoemission spectroscopy shows that the electronic environment in B-flux
crystals is superior to that of Sc-flux
crystals and produces highly resolved binding-energy peaks for B 1s and Sc 2p. Work-function measurements for the (11-20) plane give a value of approximately 5 eV, consistent with the highly electrically conductive nature of ScB2. These results demonstrate the viable ambient-pressure growth of ScB2, establish it as a
lattice-matched substrate candidate for Al-rich AlGaN power microelectronics, and show that this growth route enables scalable manufacturing of ScB2 substrates.
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All authors Satya K. Kushwaha, Ahamed Raihan, Astrid D. Kengne, Daniel Joel Harrison, R. Shipra, Han Xie, Evan N. Crites, Allana G. Iwanicki, Luke J. Meiler, Sharad Mahatara, Maxime A. Siegler, Renae N. Gannon, Steven R. Spurgeon, Rajeswari Kolagani, Amitayush Jhu Thakur, Stephan Lany, Patrick E. Hopkins, Jessica L. McChesney, Nancy Haegel, Tyrel M. McQueen, Michael G. Spencer, MVS Chandrashekhar
Materials Science
From Automated Simulation to Autonomous Discovery: A Hierarchical Framework for Agentic Computational Materials Science
Linggang Zhu, Jian Zhou and Zhimei Sun
The convergence of large
language models, materials-specific foundation models, and agentic artificial intelligence is reshaping the paradigm of computational materials discovery. While high-throughput computation, automated workflows, and data-driven modeling have greatly expanded the scale of materials exploration, the core scientific decision-making loop remains largely human-directed. Agentic AI introduces the possibility of systems that can autonomously reason about materials objectives, execute simulations, and refine strategies. However, the rapid emergence of such systems has created a critical need for a unified and operational framework to define, evaluate, and guide scientific autonomy in computational materials discovery. In this Perspective, we propose the Computational Materials
Agent Autonomy Level (CMA-AL) framework, a hierarchical taxonomy defining six levels of autonomous agency in computational materials science: scripted excecutor, LLM-assisted operator, adaptive explorer, experiment-ready modeler, agentic digital twin, and self-extending intelligence. We further map emerging agentic systems onto the framework and identify key scientific and technological challenges toward higher autonomy. CMA-AL provides a common
language for characterizing agentic computational materials discovery, evaluating the maturity of emerging systems, and guiding their
evolution toward increasingly autonomous materials discovery.
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Materials Science
Orbital-engineered px,y-kagome lattice in a halogen monolayer
Xulin Liu, Jingyi Duan, Yueqian Chen et al. (+11 more)
Multi-orbital kagome
lattices with explicit orbital degrees of freedom remain largely unexplored, as most experimentally realized systems rely on complex d-electron
manifolds that are approximated by isotropic single-orbital models. Here, we overcome this limitation by realizing a px,y-orbital kagome
lattice through deposition of a Br monolayer on Ag(111), where orbital filtering selectively suppresses the pz channel. Scanning tunneling microscopy, angle-resolved photoemission spectroscopy, and density-functional-theory calculations reveal a large-area, highly ordered kagome structure whose band dispersions quantitatively match the anisotropic px,y tight-binding model. To extract the intrinsic
manifold from the substrate background, we construct an effective H-passivated model, which uncover the intrinsic electronic structure and reveals nontrivial topological characteristics of the px,y kagome
manifold driven by first-order
spin-orbit coupling effect. Our work establishes Br/Ag(111) as an experimentally accessible platform for multi-orbital kagome physics, extending the kagome paradigm from the conventional d-orbital regime to an orbitally engineered topological setting.
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All authors Xulin Liu, Jingyi Duan, Yueqian Chen, Wenbo Liu, Peiyao Xiao, Yuxiang Liu, Pei Liu, Minjun Wang, Baojie Feng, Dongfei Wang, Xun Shi, Wei Jiang, Yugui Yao, Wende Xiao