Peer Revenue Impact factor: volatile

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Condensed Matter Materials Science

cond-mat.mtrl-sci Watch Materials Science

Sunday 30 August

Materials Science

Floquet Topological Spin-Valley-Layertronics on a Layered Dice Lattice

Jianqi Zhong, Teng-Fei Ying, Jinyu Zou et al. (+1 more)

The recent discovery of long-sought dice flat band in layered YCl electride has opened up rich possibilities of correlation and topological physics in dice lattice systems [Nature Communications 17, 2213 (2026), arXiv:2509.05958]. Here, we reveal a plethora of distinctive correlated topological phases in a generic layered dice lattice system at band filling of $\nu =4$ under on-site Hubbard interactions: (i) the system is an intrinsic sublattice anti-ferromagnetic (AFM) quantum spin-valley Hall insulator; (ii) a circularly polarized light (CPL) drives the AFM spin-valley insulator into a Floquet odd-parity $f$-wave altermagnet(AM) insulator; (iii) a vertical displacement field turns the Floquet $f$-wave AM insulator into a spin-valley-layer-polarized Chern insulator, with the sign of spin, valley and Chern number all controlled by the direction of the displacement field. Our results not only establish the layered dice lattice as a versatile platform for electrically switchable magnetic and topological phases, but also provide an all-electrical scheme for integrated spin-valley-layertronics for non-volatile information storage and processing.
Read the full abstract

All authors Jianqi Zhong, Teng-Fei Ying, Jinyu Zou, Benjamin T. Zhou

Materials Science

Valley-Enabled Intrinsic Dresselhaus Spin-Orbit Coupling in Silicon

Johannes L. P. Steinschuld, Hendrik J. Bluhm, Lars R. Schreiber et al. (+1 more)

We develop a symmetry-based theory of spin-orbit-valley coupling in silicon that reveals an intrinsic source of Dresselhaus spin-orbit coupling independent of interfaces or external electric fields. Treating the valley degree of freedom as a symmetry-carrying quantum degree of freedom, we show that the Dresselhaus interaction is necessarily valley off-diagonal and that a bulk contribution proportional to the valley Pauli matrix $\tau_1$ is symmetry allowed. Tight-binding calculations yield a bulk coupling more than an order of magnitude larger than typical interface-induced spin-orbit coupling; achieving the same energy scale through the interface-induced mechanism would require electric fields roughly 50 times larger than typical fields. We further derive the symmetry-allowed spin-valley couplings generated by magnetic-field gradients and show how they account for the valley-dependent Zeeman splitting observed in micromagnet experiments. A slight tilt of the background magnetic field out of the plane produces an additional isotropic contribution linear in $B_z$, providing an experimentally accessible signature of the corresponding coupling constant. Finally, we predict a spin-independent micromagnet-induced valley splitting in the $\tau_3$ channel, which is distinct from the $\tau_{1,2}$ channels generated by alloy disorder and therefore remains robust against disorder-induced cancellation. These results establish valley symmetry as a fundamental ingredient in the spin-orbit physics of silicon and provide new mechanisms for controlling and probing spin and valley degrees of freedom in silicon quantum devices.
Read the full abstract

All authors Johannes L. P. Steinschuld, Hendrik J. Bluhm, Lars R. Schreiber, Seyed Akbar Jafari

Materials Science

Phonon-Localization-Driven Decoupling of Dual-Channel Transport for Record-Low Intrinsic Lattice Thermal Conductivity

Zhunyun Tang, Xiaoxia Wang, Jin Li et al. (+4 more)

A fundamental bottleneck in pushing the intrinsic lattice thermal conductivity of inorganic crystalline solids to its lowest limit arises from the inherent competition between the particle-like propagation (\(\kappa_{\mathrm{L}}^{\mathrm{P}}\)) and wave-like tunneling (\(\kappa_{\mathrm{L}}^{\mathrm{C}}\)) channels. Herein, we demonstrate that phonon localization provides a robust pathway to decouple the dual-channel transport, achieving record-low \(\kappa_{\mathrm{L}}\) in quasi-1D ternary helical crystals. Despite the structural complexity leading to densely populated phonon branches and thus inducing abundant coherent phonons, the weak interchain interactions and heavy elements compress numerous branches into highly localized, nearly dispersionless flat bands. Such strong localization simultaneously suppresses both the diagonal and off-diagonal components of the group velocity, thereby synergistically suppressing \(\kappa_{\mathrm{L}}^{\mathrm{P}}\) and \(\kappa_{\mathrm{L}}^{\mathrm{C}}\). Taking InSeI as an example, the interchain room-temperature \(\kappa_{\mathrm{L}}^{\mathrm{P}}\) and \(\kappa_{\mathrm{L}}^{\mathrm{C}}\) are 0.145 and 0.053 W/mK, respectively, yielding an ultralow total \(\kappa_{\mathrm{L}}\) of 0.198 W/mK. Weaker interchain interactions further drive the room-temperature \(\kappa_{\mathrm{L}}\) of GaSeI and AlSeI to record lows of 0.086 and 0.089 W/mK, respectively; these values even drop to 0.058 and 0.059 W/mK at 900 K. These findings provide useful insights into exploring the thermal conductivity limit in crystals.
Read the full abstract

All authors Zhunyun Tang, Xiaoxia Wang, Jin Li, Chaoyu He, Chao Tang, Mingxing Chen, Tao Ouyang

Materials Science · Cross-listed from cond-mat.supr-con

Magnetic contacts on freestanding superconducting LaAlO$_3$/SrTiO$_3$ micromembranes

Thies Jansen, Pinelopi Konstantinopoulou, Niklas Martin et al. (+5 more)

The superconducting two-dimensional electron gas (2DEG) at the LaAlO$_3$/SrTiO$_3$ (LAO-STO) interface is a promising platform for superconducting spintronics, however, integrating ferromagnetic contacts with the superconducting 2DEG remains challenging. Here, we realize superconducting LAO-STO micromembrane devices contacted by ferromagnetic nickel contacts through a side-contact geometry. Low-temperature transport measurements demonstrate that superconductivity is preserved in the presence of the ferromagnetic contacts. We show that the superconducting state is strongly influenced by the magnetic history of the nickel contacts, which generates a tunable effective magnetic field in the 2DEG. Through an effective field model, the magnetization of the contacts can be inferred from the maximum superconducting response. Our results establish ferromagnetically contacted LAO-STO as a platform for future investigations of spin injection into oxide superconductors and provide a route towards superconducting spintronic devices based on complex oxide interfaces.
Read the full abstract

All authors Thies Jansen, Pinelopi Konstantinopoulou, Niklas Martin, Fabio Miletto Granozio, Alessia Sambri, Rasmus Bjørk, Felix Trier, Thomas S. Jespersen

Materials Science

High-Field Terahertz Spin Resonance in Cr$_2$O$_3$ above the Spin-Flop Transition

Kaiyang Huang, Yuto Kinoshita, Natsuki Kanda et al. (+4 more)

We report single-shot terahertz time-domain spectroscopy of Cr$_2$O$_3$ in pulsed magnetic fields up to 30 T. Well above the spin-flop field, in the 20-30 T range, the resonance frequency exhibits a nearly linear field dependence with a slope of ~22 GHz/T, smaller than the 28 GHz/T reported from low-field measurements. This reduction is insensitive to temperature and to a 15{\deg} field tilt, suggesting an intrinsic high-field property.
Read the full abstract

All authors Kaiyang Huang, Yuto Kinoshita, Natsuki Kanda, Takuya Matsuda, Masashi Tokunaga, Ryusuke Matsunaga, Yasuhiro H. Matsuda

Materials Science

Evaluating a 4B open-weights local LLM for agentic DFT workflows: a literature reproducibility audit

Shambhu Bhandari Sharma

Agentic workflows in materials science relying on hosted commercial models face severe reproducibility, economic, and data-privacy constraints. To explore fully local agentic science, this work evaluates an open-weights Qwen3:4B model executing an autonomous scientific pipeline across varying hardware constraints. Applied to pentagonal two-dimensional materials, the system extracts parameters from unstructured text, translates them into density functional theory (DFT) inputs, and drives simulations to convergence under a strict neurosymbolic architecture where agents propose and deterministic code disposes. The workflow is guarded by verbatim text grounding and multi-pass inference unions to counteract hardware-induced structural collapse. Evaluated against 201 expert judgements, the extractor achieves 95.7% precision (95% CI 90.3-98.1%) and 67.3% recall (59.8-74.0%), ensuring extracted parameters are strictly factual. However, precision identifying absent parameters does not exceed 47.0%, establishing that the measured omission rate constitutes a loose upper bound on true literature incompleteness. Across three hardware configurations, complete GPU residency governs extraction quality more fundamentally than weight or cache precision, raising Matthews correlation from 0.414 to 0.530 at fixed quantisation and to 0.560 with an unquantised cache. A corpus-scale audit indicates only 19 (33.3%) of the 57 studies are reproducible in principle, reporting every method parameter needed to re-initialise the calculation. Driven to convergence, the workflow reproduces published lattice constants with a mean absolute relative error of 2.3% where the relaxed structure retains its prototype, establishing that lightweight open-weights models can reliably drive autonomous agentic workflows when bounded by deterministic code gates.
Read the full abstract

Materials Science

Solid and Quasi-Solid Electrolytes for Zinc Batteries: Balancing Water Activity, Ion Transport, and Interfaces

Souvik Naskar, Jiaqian Qin and Eric Jianfeng Cheng

Zinc batteries offer a compelling route to safe and low-cost energy storage, yet their reliance on aqueous electrolytes promotes hydrogen evolution, corrosion, cathode dissolution, and non-uniform zinc deposition. Replacing the liquid with a solid or quasi-solid electrolyte can suppress these processes, but it also removes the medium that enables rapid Zn2+ transport and conformal electrode contact. This tension, the price of removing water, has been obscured by inconsistent use of the term solid state and by comparisons based largely on bulk ionic conductivity. Here we critically examine zinc electrolytes across a continuum from water-rich hydrogels to dry polymers, solvated crystals, and inorganic conductors. We distinguish water content from thermodynamic water activity and classify these materials according to phase state, mobile-solvent fraction, and dominant transport mechanism. We show that neither high conductivity nor nominally water-free composition reliably predicts cell performance: electrolyte thickness, Zn2+ transference, interfacial resistance, and evolving contact often determine the practical outcome. Controlled-solvation and hybrid electrolytes therefore provide the most credible near-term path, whereas genuinely solvent-free Zn2+ conductors remain a longer-term scientific target. Progress will require transparent reporting of solvent state and validation using thin electrolytes, realistic electrode loadings, limited zinc excess, and calendar-life testing.
Read the full abstract

Saturday 29 August

Materials Science

Exact benchmarks for the plasmon-pole approximation: Multi-scale screening and the breakdown of the quasiparticle picture

Michael O. Atambo

The $GW$ approximation is the gold standard for calculating quasiparticle band structures, yet its computational cost frequently necessitates the use of the plasmon-pole approximation (PPA). While PPA is known to be highly accurate for simple metals and weakly correlated semiconductors, its regime of validity in materials with competing energy scales remains poorly quantified. Here, we construct an exact, numerical benchmark of the PPA using the Lehmann representation of the density response on finite one-dimensional Hubbard clusters. By analytically convolving the exact non-interacting Green's function $G_0$ with the exact pole representation of the screened interaction $W$, we compute the $GW$ self-energy without numerical frequency integration. We demonstrate that in single-scale Mott insulators, the moment-conserving PPA is essentially exact. However, in multi-band semiconductors where interband transitions introduce a low-energy screening channel that competes with high-energy Mott fluctuations, the PPA systematically misjudges the quasiparticle gap by several electron-volts. Furthermore, we show that strong multi-pole screening can drive the exact quasiparticle weight $Z \to 0$, destroying the quasiparticle picture-an effect entirely missed by the PPA, which artificially stabilizes sharp quasiparticles. Finally, we propose a computationally inexpensive diagnostic based on the polydispersity of the loss function's spectral weight, which accurately predicts PPA failure ab initio. Our results provide a rigorous framework for assessing the validity of dynamical screening approximations in strongly correlated materials.
Read the full abstract

Materials Science

Vibrational Origin of the Barocaloric Effect in the Spin-Crossover Complex Fe(pap-5NO2)2: A Combined DFT and Mean-Field Study

Alan de Souza, Antonio M. dos Santos, Yongqiang Cheng et al. (+2 more)

Despite the barocaloric performance recently reported for the spin-crossover complex Fe(pap-5NO2)2, the microscopic origin of its pressure-induced entropy change remains poorly understood. In particular, the relative contributions of vibrational, configurational, and spin degrees of freedom to the barocaloric response have not yet been quantitatively established. Here, we develop a theoretical framework that combines density functional theory (DFT) calculations with an effective mean field Hamiltonian to investigate the barocaloric effect in this spin-crossover complex. Vibrational frequencies of the low-spin (S = 0) and high-spin (S = 2) states obtained from first-principles calculations are incorporated into a thermodynamic model that explicitly accounts for configurational, spin, and lattice entropy contributions. By establishing a correspondence between the vibrational spectra of both spin states through displacement-vector overlap analysis, we identify low and mid frequency metal-ligand vibrations as the primary microscopic origin of the vibrational entropy change. The proposed model quantitatively reproduces the experimentally reported barocaloric entropy change for a pressure variation of 2 kbar, corresponding to a maximum reversible entropy change of approximately 70 J kg-1 K-1, and predicts a spin-crossover temperature of T_1/2 = 313 K under ambient pressure, in excellent agreement with the experimental value of 308 K. Analysis of the entropy components reveals that lattice entropy associated with molecular vibrations accounts for approximately 84% of the total barocaloric response, whereas configurational and spin contributions are comparatively small.
Read the full abstract

All authors Alan de Souza, Antonio M. dos Santos, Yongqiang Cheng, Vinícius S. R. de Sousa, Mario Reis

Materials Science

PINN-Phase: A physics-informed neural network for curvature-driven multiphase-field evolution

Seifallah Elfetni, Sascha Thinius, Peter H. Seeberger et al. (+1 more)

Phase-field simulation of polycrystalline microstructures becomes costly when many related cases must be evolved over long times. We introduce PINN-Phase, a physics-informed neural time integrator that advances the full multiphase field from its initial condition and enforces phase bounds and unit sum at every step. On the reported explicit multiphase-field path, it learns from the governing residual on its own predicted states, without post-initial-condition reference states in the loss or checkpoint selection. A fixed 25-grain model satisfies the complete predefined criteria in seven of eight prospectively fixed unseen microstructures and in both deliberately atypical stress cases, with 0.94-3.71% terminal label disagreement. At native 128^3 resolution, an eight-grain model trained on four initial microstructures retains 98.79% label agreement and exact survivor identities on a training case after 24,000 autonomous steps, 5.86 times its represented training horizon. On six prospectively fixed unseen 128^3 initial conditions, label disagreement at the last saved state within that horizon is 0.72-2.11%; after autonomous evolution to 24,000 steps, or 5.86 times the represented training horizon, five of six retain the exact terminal survivor set. At 64 grains, terminal disagreement decreases from 6.09% in the primary evaluation to 3.97% after continued training, with exact recovery of the 21-grain survivor set. These results demonstrate structurally admissible long-horizon neural integration and direct initial-condition transfer within fixed benchmark families.
Read the full abstract

All authors Seifallah Elfetni, Sascha Thinius, Peter H. Seeberger, Theodore Tyrikos-Ergas

Materials Science

Elastic properties of amorphous LiTaCl$_6$ solid-state electrolyte

Xiaolin Liu and De-en Jiang

Amorphous solid-state electrolytes are attractive candidates for safe, high-energy-density all-solid-state batteries, yet their mechanical properties remain poorly understood from a computational perspective. Here, we investigate the elastic behavior of the recently discovered amorphous superionic Li-ion conductor LiTaCl$_6$ using density-functional-theory (DFT)-based methods, including unrelaxed static, relaxed static, and strain fluctuations from molecular dynamics (MD) simulations in the isobaric–isothermal (NPT) ensemble with DFT-trained machine-learning force fields (MLFFs). While the unrelaxed static method predicts a Young's modulus an order of magnitude higher than the experiment, the relaxed static method—commonly applied to crystalline electrolytes—still overestimates the modulus by more than 170%. In contrast, the MD approach using MLFFs yields a Young's modulus of $2.84 \pm 0.26$ GPa, which quantitatively agrees with the experimental value of $2.91 \pm 0.32$ GPa. Using the MLFF-MD approach, we further predict bulk modulus (4.44 GPa), shear modulus (1.02 GPa), and Poisson's ratio (0.39) for amorphous LiTaCl$_6$ and conclude that elastically it behaves like a soft polymer or gel. These results demonstrate that amorphous superionic materials possess some unique elastic properties and that, among the methods examined, only the MLFF-MD approach yields quantitative agreement with experiment, highlighting the necessity of a dynamical treatment to simulate their elastic response, consistent with recent findings for crystalline superionic conductors.
Read the full abstract

Materials Science

Strain-Driven Electronic and Catalytic Modulation of g-C3N4/GeS van der Waals heterostructure for Photocatalytic Water Splitting

Soumendra Kumar Das, Smruti Ranjan Parida, Tapas Kumbhakar et al. (+2 more)

Photocatalytic water splitting offers a viable pathway for sustainable hydrogen production. In this study, first-principles density functional theory calculations were performed to explore the strain-dependent photocatalytic behaviour of a two-dimensional g-C3N4/GeS heterostructure. The heterostructure shows type-II band alignment with an indirect band gap of 2.17 eV, smaller than those of the individual g-C3N4 (2.81 eV) and GeS (3.31 eV) monolayers. Biaxial tensile strain up to 3% effectively modulates the band gap and band edge positions, allowing suitable alignment with water redox potentials. The calculated Gibbs free energy for the hydrogen evolution reaction ({\Delta}GHER) is 0.2 eV for the pristine heterostructure and approaches near-thermoneutral values (-/+ 0.1 eV) under +1% and +2% strain. Meanwhile, the OER overpotential decreases from 2.17 V to 0.97 V with increasing strain. AIMD simulations and optical absorption in the visible region confirm the thermodynamic stability and promising photocatalytic potential of the heterostructure for hydrogen generation.
Read the full abstract

All authors Soumendra Kumar Das, Smruti Ranjan Parida, Tapas Kumbhakar, Prasanjit Samal, Sridhar Sahu

Materials Science

Analogue Phase Change Computational Memory with High Precision Reads and Energy Efficient Writes

Ghazi Sarwat Syed, Loris Coccia, Vara Prasad Jonnalagadda et al. (+4 more)

Resistive memory technologies offer a compelling advantage for in-memory computing. However, realizing a device architecture that simultaneously achieves high computational precision, efficiency, and density has remained elusive due to inherent trade-offs among these performance metrics. Here, we introduce a com- pact phase-change memory device architecture that combines an ultra-confined active switching volume for enhanced electro-thermal efficiency with a non-insulating thin film that suppresses temporal conductance fluctuations. We analytically model and back-end integrate these devices into crossbar arrays. Even with conventional, undoped phase-change materials, the device architecture enables a computational precision approaching 6 bits, low conductance values below 50 {\mu}S with an adequate conductance window, and a viable pathway toward sub-100 {\mu}A programming currents under nominal operating voltages.
Read the full abstract

All authors Ghazi Sarwat Syed, Loris Coccia, Vara Prasad Jonnalagadda, Antonio Massimiliano Mio, Asit Ray, Matthew BrightSky, Abu Sebastian

Materials Science

Evaluating LLM-based AI agents integrated with materials synthesis tools: the case of atomic layer deposition

Angel Yanguas-Gil

This work provides an overview of the different strategies that can be used to evaluate the performance of AI models and agents based on large language models (LLMs) for materials synthesis. After providing a brief overview of the key technologies behind the current generation of AI agents based on LLMs, we summarize the different approaches to evaluating these models in the context of materials science and in particular on materials synthesis, with a specific emphasis on scenarios in which the models are directly integrated with experimental tools. We discuss evaluation strategies spanning knowledge and reasoning benchmarks, tool-use benchmarks, and closed loop benchmarks involving the interaction with experimental systems or realistic virtual tools. We use atomic layer deposition (ALD) as a case study, emphasizing how existing approaches in the literature both build from general approaches used beyond materials science and can be generalized to other materials synthesis techniques. Finally, we provide a practical evaluation framework to evaluate LLMs in the context of materials synthesis
Read the full abstract

Materials Science · Cross-listed from quant-ph

Anomalous Frequency Shift in Low-Loss Superconducting Granular Aluminum Resonators

Patrick Winkel, Daniil S. Antonenko, Vishakha Gupta et al. (+5 more)

Superconducting high-kinetic inductance materials like granular aluminum (grAl) are a versatile part of the circuit quantum electrodynamics (cQED) toolbox, provided their losses at microwave frequencies are low enough. To further advance the use of grAl in quantum devices, it is indispensable to identify the dominant loss mechanisms. The standard approach pairs electromagnetic simulations of resonator geometry with measured temperature and power dependence of resonance frequency and loss rate. Most materials follow the phenomenological theory of two-level systems (TLSs) at low temperatures, resulting in an initial decrease of the resonance frequency with increasing temperature. In our work, we observe an opposite behavior at the lowest temperatures: The resonance frequency initially increases with both temperature and readout power, contradicting the standard TLS model predictions. We are able to explain a part of the data by an alternative mechanism associated with the effect of superconducting quasiparticles in a granular system with spatially-nonuniform gap. Yet, the observed change in the resonance frequency with temperature is not matched by a proportional change in the loss rate. We also observe anomalous positive frequency responses following high-energy events, characterized by several time scales. While anomalous behavior has been reported previously in grAl, the disagreement with standard models is particularly visible in our devices thanks to their exceptionally low loss rates.
Read the full abstract

All authors Patrick Winkel, Daniil S. Antonenko, Vishakha Gupta, Neel Thakur, Pavel Kurilovich, Luigi Frunzio, Leonid I. Glazman, Robert J. Schoelkopf

Materials Science · Cross-listed from cond-mat.str-el

Crystal electric field excitations and an effective-spin-$1/2$ ground doublet in the hyperkagome magnet Yb$_3$Sc$_2$Ga$_3$O$_{12}$

Tingjun Zhang, Zehao Wang, Douglas L. Abernathy et al. (+4 more)

We use inelastic neutron scattering (INS) to determine the crystal electric field (CEF) excitations of Yb$^{3+}$ in the rare-earth hyperkagome magnet Yb$_3$Sc$_2$Ga$_3$O$_{12}$. Three nearly dispersionless magnetic excitations are observed near 58, 68, and 74~meV, corresponding to transitions from the ground-state Kramers doublet to the three excited doublets of the $J=7/2$ multiplet. A Stevens-operator analysis constrained by the local $222$ ($D_2$) symmetry reproduces the excitation energies and spectral weights and yields an Ising-type ground-state $g$ tensor. The first excited doublet lies approximately 58~meV above the ground state, establishing a well-isolated effective $J_{\mathrm{eff}}=1/2$ degree of freedom over the low-temperature regime relevant to collective magnetism. Notably, the directly measured CEF spectrum substantially revises the level scheme previously inferred from bulk measurements, while preserving the essential low-energy pseudospin description. Two independent fitting protocols give consistent excitation energies, ground-doublet wave functions, and $g$ tensors, despite the nonuniqueness of the individual CEF parameters. The resulting single-ion model also reproduces the characteristic susceptibility, magnetization, and field evolution of the Schottky anomaly in specific heat. These results establish the microscopic single-ion basis needed to construct an effective exchange Hamiltonian and to interpret future measurements of low-energy collective excitations in Yb$_3$Sc$_2$Ga$_3$O$_{12}$.
Read the full abstract

All authors Tingjun Zhang, Zehao Wang, Douglas L. Abernathy, Rong-Zhu Lin, Steven J. Gomez Alvarado, Chien-Lung Huang, Pengcheng Dai

Materials Science

Single-pulse strain-induced precessional dynamics of magnetization in Co-doped iron garnet

Héloïse Damas, Carl S. Davies, Tomasz Zalewski et al. (+4 more)

Ultrafast control of magnetization through lattice excitation provides a route to manipulating magnetic order on short timescales, yet the role of transient strain in driving magnetization dynamics remains poorly understood. Here, single-shot pump-probe magneto-optical microscopy is used to resolve the structural and magnetic responses of cobalt-doped yttrium iron garnet to individual 5-ps mid-infrared pulses. The excitation generates a localized strain field together with an outward-propagating elastic wave. Concurrently, the magnetic contrast decreases following excitation and subsequently reverses on a timescale of approximately 1.5-2 ns before recovering to its initial state. The structural and magnetic responses exhibit closely correlated wavelength and pulse-energy dependences, indicating a common excitation pathway. Micromagnetic simulations incorporating transient strain reproduce the precessional reorientation of the magnetization within individual domains while largely preserving the labyrinthine domain morphology. These results identify transient lattice deformation as the link between single-pulse mid-infrared excitation and reversible precessional magnetization dynamics in Co-doped yttrium iron garnet.
Read the full abstract

All authors Héloïse Damas, Carl S. Davies, Tomasz Zalewski, Petr M. Vetoshko, Vladimir I. Belotelov, Andrzej Stupakiewicz, Andrei Kirilyuk

Materials Science

Directional commensurability stabilizes structural superlubricity in patterned mesoscale interfaces

Viet Hung Ho, Ge Li, Melisa M. Gianetti et al. (+3 more)

Structural superlubricity, arising from lattice incommensurability, offers a promising route to eliminate friction and associated energy losses in mechanical systems. In real-world systems, roughness and wear currently pose severe limitations on its robustness and especially the contact size. Here, we consider patterned surfaces as a possible route to overcome some of these limitations. We show that the simplest choice of patterning, contacts made up of two incommensurate triangular-triangular patterns, fails at elevated loads because of the small number of load-bearing contacts, causing the maximum local contact pressure to exceed the strength of the superlubric coating. We introduce a square-triangular patterned interface that increases the number of load-bearing contacts and organizes them into continuous contact lines. When sliding along specific directions relative to these lines, superlubricity is maintained at significantly higher loads by reducing pressure-induced coating failure while also remaining somewhat tolerant to surface imperfections. These findings establish a mechanism for stabilizing structural superlubricity against coating failure and a design principle for engineering low-friction interfaces with enhanced load-bearing capacity and defect tolerance.
Read the full abstract

All authors Viet Hung Ho, Ge Li, Melisa M. Gianetti, Bjørn Haugen, Graham L. W. Cross, Astrid S. de Wijn

Materials Science · Cross-listed from cond-mat.str-el

Electronic phase separation and emergence of a nondimerized insulating phase in VO$_2$ $(110)_{\mathit{R}}$ ultrathin films

S. Inoue, D. Shiga, R. Hayasaka et al. (+3 more)

Using in situ photoemission spectroscopy and x-ray absorption spectroscopy, we investigated the thickness dependence of the electronic structure and V-V dimerization in VO$_2$/TiO$_2$ (110) ultrathin films, in which the one-dimensional V-V chains along the $c_{\mathit{R}}$ axis lie in the film plane. In VO$_2$ $(110)_{\mathit{R}}$ films, the reduction in dimensionality along the surface-normal direction is not expected to impose a geometric constraint on V-V dimerization, unlike in VO$_2$ $(001)_{\mathit{R}}$ films. Nevertheless, the characteristic spectral changes associated with the temperature-driven metal-insulator transition observed in thick films persist down to 1.5 nm, whereas at 1 nm an insulating electronic phase is observed without V-V dimerization. This behavior is highly similar to that reported for VO$_2$ $(001)_{\mathit{R}}$, suggesting that the enhancement of Mott instability resulting from reduced dimensionality is a common and essential driving force for the emergence of the nondimerized insulating phase in VO$_2$ ultrathin films. Meanwhile, unlike in VO$_2$ $(001)_{\mathit{R}}$, the nondimerized insulating phase in VO$_2$ $(110)_{\mathit{R}}$ coexists with the phase exhibiting the temperature-driven metal-insulator transition. Its fraction increases exponentially with decreasing thickness and becomes dominant at 1 nm. The corresponding effective critical thickness is estimated to be 2.2 nm. These results imply that the geometric orientation of the V-V chains dictates the spatial evolution of electronic phase separation via strain-mediated phase competition.
Read the full abstract

All authors S. Inoue, D. Shiga, R. Hayasaka, K. Ozawa, A. F. Santander-Syro, H. Kumigashira

Materials Science · Cross-listed from cond-mat.str-el

Real-space manifestation of ferroic multipoles in altermagnetic MnF$_2$

Iurii Kibalin, Dalila Bounoua, José A. Rodriguez Velamazán et al. (+9 more)

Altermagnets are unconventional spin split magnets arising from the zero spin-orbit coupled limit. They host a magnetic multipolar order parameter yet direct real-space observation of these multipoles has remained elusive. Here we use polarized-neutron diffraction to reconstruct the three-dimensional magnetization density of the prototypical altermagnet MnF$_2$. By exploiting symmetry-selective magnetic reflections, we separate the dominant spherical Mn$^{2+}$ contribution from the much weaker anisotropic Mn magnetization and the covalent spin polarization of the fluorine ligands. The reconstructed spin density reveals a finite fluorine ion moment together with an anisotropic Mn magnetization consistent with the symmetry-allowed altermagnetic rank-5 magnetic multipole $O_{52}$(magnetic triacontadipole). These results provide direct real-space evidence of ferroic multipolar order in an altermagnet and establish polarized-neutron diffraction as a powerful probe of hidden magnetic multipoles in quantum materials.
Read the full abstract

All authors Iurii Kibalin, Dalila Bounoua, José A. Rodriguez Velamazán, Oscar Fabelo, Navid Qureshi, Quentin Faure, Philippe Bourges, Victor Balédent, Jian-Rui Soh, Jeffrey Rau, Paul McClarty, Arsen Gukasov

Materials Science

Can a Spin Liquid State Persist as the Ground State in the Presence of Competing Interactions and Disorder?

Sumanta Mukherjee

In this report, we have shown that, in an otherwise geometrically frustrated lattice, the underlying interactions compete to stabilize different magnetic phases. In conjunction with fluctuations, these interactions may lead to the formation of unusual ordered phases, providing a pathway for understanding the fluctuation-driven order-by-disorder phenomenon. This competition is further modified by the presence of inherent structural disorder in a frustrated two-dimensional lattice. Furthermore, due to the local nature of the additional structural disorder, the majority of the samples evolve toward glassy dynamics, which can not only mimic spin-liquid-like behavior but also make it difficult to identify genuine spin-liquid candidates experimentally.
Read the full abstract

Materials Science

Orbital occupation selects structural dimensionality in binary transition-metal oxides

Deping Guo, Renhong Wang, Cong Wang et al. (+6 more)

Orbital-lattice coupling in transition-metal oxides is usually discussed within a given bonding framework, where orbital occupation is intertwined with local coordination, strain, or symmetry breaking. Here, we show that orbital occupation can also select the bonding framework itself, thereby determining structural dimensionality. Using first-principles calculations, we identify CrO as a prototype in which the single active $3d\,e_g$ electron of high-spin Cr$^{2+}$ gives rise to two competing orbital-structure states. The $d_{x^2-y^2}$ occupation favors a three-dimensionally connected covalent phase, whereas the $d_{z^2}$ occupation stabilizes a weakly coupled layered phase. Constrained-occupation calculations show that increasing the $d_{z^2}$ filling continuously contracts the in-plane lattice while expanding the structure along the layer normal. The two phases exhibit distinct magnetic ground states and ferroelastic responses. Moreover, the layered phase is robust against exchange-correlation functional and on-site ($U$) variations, remains dynamically stable down to the monolayer limit, and has a low exfoliation energy of 46 meV/Angstrom^2. Extending the analysis across related $3d$ binary oxides reveals a filling-dependence relation between accessible orbital filling and the preference for 2D or 3D connected bonding motifs, providing a microscopic basis for exploring low-dimensional oxide materials.
Read the full abstract

All authors Deping Guo, Renhong Wang, Cong Wang, Meng Gao, Wu Zhou, Yanning Zhang, Fei Pang, Zhihai Cheng, Wei Ji

Materials Science

Symmetry-Preserving Phase Transitions in $AM_2$Al$_9$ Materials under Pressure

Jian-Feng Zhang, Sheng Xu, Zhong-Yi Lu et al. (+1 more)

External parameters such as temperature, pressure, and chemical doping can induce structural phase transitions in materials. Although such transitions usually involve a change in symmetry, an uncommon exception is the isostructural phase transition, which is first order yet preserves the symmetry of the parent structure. Using first-principles calculations, we show that $AM_2$Al$_9$ compounds ($A$ = Ba, Ca, Sr, or Eu; $M$ = Fe, Co, or Ni) undergo pressure-induced isostructural phase transitions. At the transition pressure, these systems exhibit a pronounced volume collapse while retaining the same crystal symmetry and space group ($P6/mmm$). Bonding analysis based on the integrated crystal orbital Hamilton population (ICOHP) shows that the transition is driven by a redistribution of bonding character between intralayer and interlayer atomic bonds. Because isostructural transitions are rare in single crystals, $AM_2$Al$_9$ provides a promising platform for investigating critical phenomena under pressure and for deepening our understanding of symmetry-preserving structural transitions.
Read the full abstract

All authors Jian-Feng Zhang, Sheng Xu, Zhong-Yi Lu, Tao Xiang

Friday 28 August

Materials Science

Symmetry-protected intraband exciton-phonon scattering and its breakdown by mass asymmetry

Michael O. Atambo

The coupling of excitons to lattice vibrations is typically treated via phenomenological models that artificially separate long-range Fröhlich and short-range Holstein interactions. Recent analytical work has established that, in the delocalized limit, Fröhlich scattering is suppressed by electron–hole interference. Here we present a model-space Bethe–Salpeter framework to evaluate exciton–phonon coupling across the extended-to-localized crossover. We establish a fundamental distinction between the inclusive exciton–phonon coupling weight, obtainable via an exact completeness sum rule without summation over excited states, and the exclusive intraband (internal-state-preserving) scattering amplitude that governs low-energy decoherence. We prove an exact symmetry theorem: for an inversion-symmetric relative-coordinate Hamiltonian with equal electron and hole masses, the intraband Fröhlich vertex vanishes identically, protecting the exciton from low-energy polar phonon scattering. When mass asymmetry is introduced, the finite-momentum relative wavefunction acquires a complex phase twist that breaks this protection. By analyzing the long-wavelength limit, we derive a controlled small-$q$ activation law showing that the intraband vertex scales as $F_{00}(q) \propto \Delta q^2 \langle r^2 \rangle$, where $\Delta$ parameterizes the mass asymmetry. Finally, we compute the second-order polaron self-energy shift and demonstrate that mass asymmetry dramatically enhances phonon dressing, confirming that the symmetry theorem directly governs the many-body energy renormalization of the exciton. These results provide a rigorous conceptual framework for understanding the competition between long-range and local exciton–phonon coupling in polar semiconductors.
Read the full abstract

Materials Science · Cross-listed from math.NA

Semidiscrete Modeling of Dislocation-Disclination Systems: Finite Element Formulation

Pierluigi Cesana, Edoardo Fabbrini, Andrés A. León Baldelli et al. (+1 more)

We present a numerical formulation for the resolution of finite systems of interacting edge dislocations and wedge disclinations. The approach is based on a finite element discretization of a fourth-order elliptic boundary value problem arising from the mechanical equilibrium equations of plane-strain linear elasticity in the presence of kinematic incompatibilities. The numerical implementation follows a continuous interior penalty discontinuous Galerkin framework and relies on the solution of a finite set of local cell problems. Our method is validated against analytical benchmarks and used to explore several non-trivial dislocation-disclination configurations, illustrating how translational and rotational incompatibilities shape the stress state of the body.
Read the full abstract

All authors Pierluigi Cesana, Edoardo Fabbrini, Andrés A. León Baldelli, Marco Morandotti

Materials Science · Cross-listed from physics.chem-ph

Unraveling the PFAS helix: A statistical approach

Pranoy Ray, Haden Cavalli, Gashaw Bizana et al. (+5 more)

The extreme persistence of per- and polyfluoroalkyl substances (PFAS) in the environment is rooted in their three-dimensional molecular conformation. The helical twist adopted by perfluoroalkyl chains due to hyperconjugation involving their recalcitrant C-F bonds governs their resistance to degradation, yet a quantitative, continuous metric for helicity has remained absent. Here we introduce a data-driven framework that quantifies backbone helicity using three statistical descriptors: void-state (binary occupancy) spatial autocorrelations, local backbone principal component analysis, and persistent homology. We further validate each statistical descriptor against geometric dihedral benchmarks and DFT-calculated Vibrational Circular Dichroism (VCD) spectra. The framework is initially established on a homologous series of perfluorocarboxylic acids (FC2 through FC16) and their hydrogenated analogues, then extended across perfluorosulfonic acids, fluorotelomer alcohols, polyfluoroalkyl hexanoic acid analogues, and longer-chain PFOA and PFOS analogues. Agreement between statistical, geometric, and spectroscopic definitions of helicity is established for PFCAs and extended to structurally distinct subfamilies, including PFOA analogues of varying fluorine content and perfluorosulfonic acids, demonstrating that the descriptors are robust to changes in headgroup chemistry and fluorine substitution pattern. The framework provides a chemistry-agnostic toolset for incorporating backbone conformation into predictive models of PFAS environmental fate and degradation reactivity.
Read the full abstract

All authors Pranoy Ray, Haden Cavalli, Gashaw Bizana, Andrew R. Castillo, Shubham Vyas, Ronald L. Siefert, Surya R. Kalidindi, Manoj Kolel-Veetil

Materials Science · Cross-listed from cond-mat.mes-hall

Coherent phononic frequency combs in ferroelectric CMOS oxides

Jinghan Gao, Shruti Mishra, Yilin Kou et al. (+3 more)

Modern electronic systems require tens of clock and carrier frequencies, each synthesized by a dedicated phase-locked loop from a shared reference, imposing routing, power and synchronization burdens that grow with every domain. Optical frequency combs solved this problem in photonics, whereas electronics has lacked an equivalent source in its native radiofrequency domain. Here we report broadband phononic frequency combs in ferroelectric hafnia-zirconia nanoelectromechanical resonators built from complementary metal-oxide-semiconductor (CMOS) oxides. Lithographically defined detuning of a 2:1 internal resonance selects the generation mechanism: two-tone-seeded wave mixing yields more than 170 lines distributed over two octaves, with mutual coherence verified for representative pump and generated lines, whereas an autonomous Hopf route yields hierarchical combs of more than 200 lines through torus and period-doubling dynamics, in agreement with slow-flow bifurcation theory. Geometric scaling extends comb generation across 0.44 GHz to 2.1 GHz. Heterodyne measurements, analyzed using the modified Allan deviation (MDEV), establish a two-timescale law. The mechanism governs short-term stability: seeded combs inherit the white-phase-noise scaling of their pumps, whereas autonomous combs acquire the phase diffusion of a free-running oscillator, with the one-second MDEV increasing from 1e-11 to 1e-8. The material governs long-term stability: in air and without active thermal control, the temperature-compensated stack suppresses the random-walk drift that dominates uncompensated resonators. These results establish mechanism- and material-level design rules for operating a single resonator as chip-scale frequency infrastructure, from multi-clock generation to radiofrequency parallel processing.
Read the full abstract

All authors Jinghan Gao, Shruti Mishra, Yilin Kou, S M Enamul Hoque Yousuf, Hanna Cho, Roozbeh Tabrizian

Materials Science

Giant staggered Dzyaloshinskii-Moriya vectors emerged in synthetic antiferromagnets with spatially alternating stress

Yuuga Iwata, Kensuke Hayashi, Reiju Furumaki et al. (+3 more)

Dzyaloshinskii-Moriya (DM) interaction is a source of chiral magnetic physics, and it manifests microstructural symmetry which could link to exotic magnetic and electronic properties such as altermagnetism. For a new paradigm in magnetism and spintronics, it is crucial to have control on the DM interaction as well as ordering of the DM vectors which characterize the DM interaction. Here, we report on a strong interlayer DM interaction emerged in Co/Ru magnetic superlattices whose structural symmetry is unambiguously broken by alternating mechanical strains developed using the peculiar technique of our stress mechanism. Moreover, theoretical analyses reveal that our magnetic superlattices host a staggered order of the DM vectors. Our results indicate that the spatially varying strains with our breakthrough technique are quite effective in breaking the symmetry of the system and prove that it can control the DM interaction strength as well as the DM vector order.
Read the full abstract

All authors Yuuga Iwata, Kensuke Hayashi, Reiju Furumaki, Satoshi Iihama, Masahiro Sato, Takahiro Moriyama

Materials Science

Energy landscape and dissipation of sliding magnetic rotor arrays

Johannes Krotz and Anton Lüders

Magnetically coupled damped rotational degrees of freedom can give rise to tribological loss when excited by a relative sliding motion, linking friction to the dynamics of magnetic moments. We analytically investigate such magnetic friction by studying a recently introduced simplified model for a rigid magnetic rotor array sliding over a commensurate magnetic substrate. Here, the array rotors can rotate about an axis perpendicular to the sliding direction and are damped by microscopic shaft friction, while the substrate magnets have a fixed in-plane orientation. The simplified model reduces the collective rotor dynamics of this setup to a set of coupled nonlinear differential equations, which can be studied by the corresponding energy landscape in the quasi-static regime. We find that the parameter plane spanned by layer separation and time can be divided into distinct chambers, in which the structure of the energy landscape remains invariant. Using these chambers, we identify the layer separation intervals corresponding to different dynamical states and recover the emergence of a regime where the moment alignment alternates globally while exhibiting peak dissipation. Additionally, we derive the leading nontrivial orders of the collective magnetic friction in the regimes of small and large gaps between the array and the substrate. For the alternating regime, we find that friction can be computed by tracking energy jumps from unstable to stable critical points at the chamber boundaries. These results provide an analytical foundation for the observed dynamics and dissipation in sliding rotor arrays. Because the simplified model is scale-free, our conclusions transfer across a broad range of microscopic and macroscopic length scales.
Read the full abstract

Materials Science

Revealing low-energy surfaces of multinary compounds by controlling surface coordination environments

Weihang Xie, Harshan Reddy Gopidi, Zhengyu Liu et al. (+5 more)

When modeling surfaces of multinary compounds, conventional cleavage planes often cut through strongly bonded polyhedra, resulting in unphysical surface energies. Here, we introduce SALAMI (Symmetric Atomic Layers for Arbitrary Multinary Interfaces), a Python package that generates symmetric, charge-neutral, dipole-free, and low-energy slab models for multinary compounds. SALAMI performs combinatorial searches to selectively remove surface atoms and generate corrugated terminations that preserve optimal coordination environments. We applied this workflow to all symmetrically inequivalent crystallographic orientations with Miller indices up to 2 for two prototypical structures: the solid-state electrolyte Li3PS4 and the transparent conducting oxide ZnSb2O6. Density functional theory calculations reveal that Li3PS4 must preserve all PS4 units to achieve the minimum surface energy. For ZnSb2O6, low-energy surfaces are achieved by partial undercoordination of surface Sb atoms to SbO5 or SbO4 from the bulk SbO6, depending on the surface orientations. Compared to surface models generated with unconstrained coordination, applying constraints to achieve optimal local coordination environments significantly lowers surface energies, shrinking the volume of the predicted Wulff shape by approximately 20%. Our results demonstrate that meticulous control of local coordination environments is necessary for accurately predicting the surface energetics of multinary compounds.
Read the full abstract

All authors Weihang Xie, Harshan Reddy Gopidi, Zhengyu Liu, Romain Claes, Alexander G. Squires, Keith T. Butler, David O. Scanlon, Pieremanuele Canepa