Materials Science · Cross-listed from physics.app-ph
Sub-Micron Gate $\beta-Ga_{2}O_{3}$ FinFETs with Current Density $>$ 750 mA/mm and Ion/Ioff Ratio $>$ $10^{9}$
Nabasindhu Das, Cameron Gorsak, Pushpanshu Tripathi et al. (+7 more)
In this work, we demonstrate submicron-gate $\beta-Ga_{2}O_{3}$ FinFETs that integrate Si delta-doped channels with selectively regrown n++ source/drain contacts. The devices employ 100 nm-wide fins to improve electrostatic control of a high sheet charge density channel of $3.3\times 10^{13}$ cm-2. A 150 nm-gate-length FinFET exhibits a maximum drain current density of 764 mA/mm at VGS = 1 V and VDS = 10 V, an on-resistance of 9.1 $\Omega$.mm, and an Ion/Ioff ratio exceeding $10^9$. The device also shows a peak transconductance of 43 mS/mm and de-embedded $f_{T}/f_{MAX}$ values of 6.3/2.0 GHz. Pulsed I-V measurements indicate ~20 % current collapse, attributed primarily to trapping at etched fin sidewalls and the $Al_{2} O_{3}$/ $\beta-Ga_{2}O_{3}$ interface. These results show that delta-doped $\beta-Ga_{2}O_{3}$ FinFETs can simultaneously achieve high drive current, strong current modulation, and GHz-frequency operation, providing a scalable device platform for future power and RF electronics.
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All authors Nabasindhu Das, Cameron Gorsak, Pushpanshu Tripathi, Ankita Kashyap, Noor Jahan Nipu, Advait Gilankar, Hari Nair, Uttam Singisetti, Trevor Thornton, Nidhin Kurian Kalarickal
Soft Condensed Matter
Contact-mediated asymmetric delay and rate memory in snapping beam pairs
Gavin Linton, Shima Mahmoudirad, Nidhi Pashine et al. (+1 more)
Slender structures in dense environments interact through contact, which alters how and when they become unstable. Here we show that contact makes snap-through history dependent, so that when and whether a beam pair snaps depends on how long the contact is loaded. Under cyclic compression, the pair snaps on loading, snaps on unloading, or stays packed, with the loading and unloading rates selecting among the three. Upon contact, one beam rolls along the other without slip, and faster driving lets it roll further before it slides and snaps: to larger compression on loading and to smaller compression on unloading. This delay is asymmetric between loading and unloading as the unloading branch carries a
memory of the loading rate. Interestingly, above a threshold compression the pair snaps even when the compression is stopped, with the time to snap diverging at that threshold. By exploiting this asymmetric, rate-dependent delay, we program ordered sequences of snap events in arrays of pairs with tunable gaps, and demonstrate that the energy dissipated per cycle becomes a two-parameter function of the loading and unloading rates, increasing fourfold when, at the fastest loading, the return is slowed.
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All authors Gavin Linton, Shima Mahmoudirad, Nidhi Pashine, Anupam Pandey
Materials Science
Role of defect trapping in the enhanced corrosion resistance of Ni-Mo alloys with yttrium and yttrium oxide additions
Jia-Hong Ke, Xinchang Zhang, Jingfan Yang et al. (+3 more)
Corrosion of structural
alloys remains a critical challenge for advanced molten salt reactors, where aggressive fluoride salts promote continuous dissolution at the salt-metal interface. While most mitigation strategies emphasize thermodynamic stability, kinetic control of atomic transport has received comparatively less
attention. Here, we propose a corrosion mitigation strategy based on
diffusion control and vacancy trapping by dilute yttrium (Y) solutes and yttrium oxide (Y$_2$O$_3$) dispersions in Ni
alloys. A combined computational and experimental approach integrates density functional theory (DFT), self-consistent mean-field (SCMF)
diffusion modeling, and an impurity trapping model to quantify the impact of defect trapping on effective vacancy mobility. Strong first-nearest-neighbor vacancy-Y binding, off-
lattice vacancy configurations, and elevated rotational and dissociation barriers result in pronounced suppression of vacancy diffusivity, while Y$_2$O$_3$-associated sites treated as fixed traps in the model further reduce the mobile vacancy population. Ni-Mo (NM), Y-modified (NMY), and Y$_2$O$_3$-containing (NMYO)
alloys were tested in molten fluoride salt at 750{\deg}C. Corrosion penetration decreases systematically from NM to NMY to NMYO, consistent with the predicted reduction in vacancy-mediated transport. The same trend is observed in mass change, with net weight loss decreasing from 0.52% for NM to 0.23% for NMY and 0.09% for NMYO. These results are consistent with an
alloy-side transport contribution from defect trapping and reduced atomic transport. This study therefore suggests point defect engineering as a promising
alloy design strategy for extreme nuclear environments.
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All authors Jia-Hong Ke, Xinchang Zhang, Jingfan Yang, Qiufeng Yang, Ruchi Gakhar, Rongjie Song
Materials Science
Graphene-Confined Growth of Few-Layer PtSe2 via One-Step Selenization
Timea Ema Krajčovičová, Peter Kotrusz, Viera Skákalová et al. (+5 more)
Platinum diselenide (PtSe$_2$), a member of the transition metal dichalcogenide (TMD) family, is a promising material for next-generation electronic and optoelectronic applications due to its thickness-dependent properties, transitioning from semimetallic in bulk to semiconducting behavior at the few-layer limit. However, the scalable fabrication of large-area ultrathin PtSe$_2$ films remains challenging, as conventional selenization of pre-deposited Pt layers often leads to undesired three-dimensional clustered growth. This work explores a novel strategy for promoting two-dimensional growth of PtSe$_2$ by employing a
graphene-mediated confinement approach. The method involves coating a Pt layer with
graphene oxide (GO), followed by annealing in a selenium atmosphere, which results in the simultaneous formation of PtSe$_2$ and the reduction of GO to
graphene. The
graphene overlayer acts as a physical confinement layer, suppressing vertical growth and enabling the synthesis of
graphene-confined PtSe$_2$
heterostructures on centimetre-scale substrates and promoting lateral connectivity of PtSe$_2$ regions observed by STEM. Scanning transmission electron microscopy (STEM), including temperature-resolved in situ atomic-resolution measurements, was used to investigate the influence of selenization temperature on the growth mechanism and structural
evolution of PtSe$_2$ films. The results show that
graphene confinement stabilizes lateral growth and promotes the formation of few-layer films with improved structural ordering. Beyond PtSe$_2$, this
graphene-assisted approach provides a general strategy for fabricating and stabilizing ultrathin TMD layers, including those prone to environmental degradation, providing a new outlook for enabling detailed studies of their intrinsic properties.
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All authors Timea Ema Krajčovičová, Peter Kotrusz, Viera Skákalová, Agáta Laurenčíková, Igor Píš, Martin Hulman, Kimmo Mustonen, Michaela Sojková
Materials Science
DiffGA: Steering Frozen Diffusion Models for Materials Design via Evolutionary Search
Shivang Agarwal, Rodrigo Wang, Kevin Ryczko et al. (+1 more)
Steering candidate generation toward user-defined objectives is central to inverse materials design, yet remains difficult when objectives are black-box, changing, or non-differentiable, as in many simulation- and experiment-derived properties. Generative models offer a solution but typically require retraining or fine-tuning for each new objective, demanding labeled data and substantial compute, or rely on differentiable guidance that is brittle to gradient noise and undefined for many practical targets. We present DiffGA, a retraining-free framework that injects evolutionary search into the sampling trajectory of a retrained
diffusion model, evolving partially denoised states under an arbitrary black-box oracle. Because oracle evaluation often dominates campaign cost, we couple DiffGA with an on-the-fly
Bayesian surrogate that reuses representations from state-of-the-art machine-learned force fields (MLFFs). A Gaussian process is fit during the campaign on the force fields's graph
embeddings and, once it demonstrably ranks an unseen generation, replaces expensive property evaluations under an uncertainty-aware acquisition rule, reducing oracle cost with negligible loss of accuracy. Across three
crystal-design tasks using a frozen MatterGen backbone, DiffGA outperforms
diffusion-only, compute-matched, purely evolutionary, and fine-tuned baselines in oracle-assessed rates of stable, unique, and novel hits. Rather than proposing scientific compounds, we use density functional theory to quantify MLFF oracle fidelity, showing that it is a faithful proxy in key regimes but systematically biased in others, delineating when proxy-driven generative discovery can be trusted. On a representative sample, DiffGA's top hits survive first principles re-evaluation as physically realistic hits, while the surrogate-accelerated pipeline preserves this fidelity at a fraction of the cost.
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All authors Shivang Agarwal, Rodrigo Wang, Kevin Ryczko, Aayush R. Singh
Materials Science
EpNet-Si: Atomic Form Factors Learned from Band Structures
Qiang Zhu
The empirical pseudopotential method (EPM) computes band structures with one diagonalization per $k$ point and no self-consistency, but its fixed atomic form factors do not transfer between
crystal structures. To address this limitation, we introduce EpNet-Si, an EPM for silicon in which an equivariant network predicts each atom's plane-wave form factor from its local environment: a species potential plus monopole, dipole and quadrupole corrections, mixed by a learned router over atomic densities, together with an $s/p$ nonlocal projector. With 6{,}195 parameters, the model is trained through the eigensolver on reference density functional theory (DFT) band energies of only 77
cells. Among 231 distortions of the trained structure types, the 142 gapped
cells have mean band and gap errors of 15 and 8\,meV; among 192 unseen structures, the 165 gapped
cells have mean errors of 38 and 49\,meV. Physical properties derived from EpNet-Si, including effective masses, gap pressure coefficients, deformation potentials and the density of states at the Fermi level, agree with those obtained from the reference DFT calculations. These results suggest that the classical EPM, fitted to a small set of reference data, can be extended into a fast alternative for modern electronic band-structure calculations.
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Soft Condensed Matter
Time-temperature-composition equivalence of the viscoelastic behavior through the glass transition of digitally mixed 3D-printed polymers
Beijun Shen, Sanat K. Kumar and Mary C. Boyce
The linear viscoelastic behavior of a
polymer shows an equivalence of loading frequency and temperature, the time-temperature equivalence (TTE). Horizontal shifting extends moduli measured over limited ranges to much wider ranges, through the glass transition. Multimaterial 3D printing has created digitally mixed
polymers, a new class in which elastomeric and glassy resins are mixed voxel by voxel in prescribed ratios. Composition shifts the location and breadth of the glass transition and increases the rubbery modulus. Here we extend TTE to a time-temperature-composition equivalence (TTCE). Across all measured temperatures, frequencies, and compositions, the storage modulus collapses onto one master curve. Composition translates the transition and stretches its breadth, both linearly. The phase angle and relaxation spectrum superpose under the same operations, so the family shares one distribution of relaxation times. A single closed-form TTCE gives the storage and loss moduli of the family, guiding graded and architected designs for elasticity and dissipation.
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Soft Condensed Matter
A Minimal Theoretical Model for Morphodynamic Selection in Soft Matter Systems
Weihua Mu and Da Wang
Soft matter systems often display shape transitions, mode competition, and threshold-like dynamical responses driven by the coupling between mechanics, geometry, and biochemical or active fields. Here we present a minimal theoretical framework for describing such morphodynamic selection using a small number of physically interpretable order parameters. The model combines elastic relaxation, active driving, and nonlinear feedback, yielding distinct regimes corresponding to weak deformation, single-mode selection, and coupled shape transformation. We derive the governing equations, identify the relevant dimensionless control parameters, and show how the phase behavior can be organized in terms of threshold competition and effective coupling strengths. The framework provides a compact route for connecting analytical theory, numerical simulations, and experimentally observable shape dynamics in soft and biological matter.
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Materials Science
Investigation on Thermal Stability of Epi-GeSn Directly on Si (001)
Tharundev V V, Dushyant Singh, Vigneshswari SR et al. (+3 more)
In this paper we investigate the structural properties and thermal stability of metastable Ge1-xSnx epilayers (~4.5 at.% Sn) grown directly on Si(001) substrates by high-resolution X-ray diffraction (HRXRD) and Raman spectroscopy. Our results demonstrate that both 70 and 140 nm films are fully relaxed, with the thicker film exhibiting a small tensile strain (+0.09%). The thermal stability of the
heterostructures was evaluated up to 813 K using temperature-dependent Raman spectroscopy and scanning electron microscopy. The surface-weighted Raman response (532 nm excitation) and surface morphology of the 70 nm film remain highly stable. In contrast, the 140 nm film undergoes severe degradation, characterized by significant attenuation and broadening of the Ge-Ge longitudinal optical
phonon mode, alongside enhanced surface Sn segregation. These findings demonstrate that the thermal stability of direct GeSn/Si
heterostructures is governed by the initial defect structure established during epitaxial growth, providing key design rules for understanding the fabrication of GeSn-based optoelectronic devices.
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All authors Tharundev V V, Dushyant Singh, Vigneshswari SR, Subha Maity, Prince Rathor, Krista R Khiangte
Disordered Systems and Neural Networks · Cross-listed from q-bio.NC
Full Lyapunov Spectra of Random Neural Networks, Part I: Finite-Time and Asymptotic Theory
Haoyu Albert Wang and Wei P. Dai
We develop a dynamical mean-field framework for the full finite-time and stationary asymptotic Lyapunov spectra of random recurrent neural networks. At finite observation time, an exact log-determinant representation of tangent-propagator singular values leads to a closed-contour
matrix Dyson equation for the smoothed spectral tail. In the stationary setting, a cocycle representation yields an operator equation for the asymptotic cumulative spectrum. Both formulations retain complete local gain histories and the repeated action of quenched connectivity. Direct singular-value calculations and network QR spectra support the predictions in the regimes examined, with sampling uncertainty and numerical cutoffs assessed separately. The stationary equation also recovers the known maximal exponent, and controlled gain-history replay illustrates how temporal correlations redistribute instability. This work was carried out in collaboration with ChatGPT 5.6 Sol. Toward the end of preparation we became aware of David G. Clark's contemporaneous work, Lyapunov spectrum of random neural networks[arXiv:2610.12426], which reports overlapping mean-field results for the full Lyapunov spectrum using a cavity approach.
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Materials Science
Pressure-Driven Evolution of the Physical Properties of Layered Y2GaB and Y2InB MAB Phases: A Comparative First-Principles Study
M. Rabi Us Sani Shapon, Md. Asif Afzal, Jubair Hossan Abir et al. (+2 more)
MAB phases are nanolaminated ternary borides in which strong in-plane M-B bonds and weaker interlayer interactions drive their distinctive stability and functionality. Hydrostatic pressure offers a direct route to tune the in-plane and interlayer interactions that govern the stability and functionality of layered Y2GaB and Y2InB borides. Here, first-principles calculations are used to compare their structural, elastic, thermophysical, electronic, bonding, optical, and vibrational responses from 0 to 20 GPa. Elastic criteria show that Y2GaB is stable at 0, 5, and 10 GPa, whereas Y2InB is stable only at ambient pressure. Within the stable Y2GaB range, compression increases the elastic moduli, acoustic velocities, Debye temperature, and
lattice thermal conductivity while reducing the elastic anisotropy. Both compounds are multiband metals and
spin-orbit coupling modifies local dispersions without opening a gap. Y2GaB retains nine Fermi-surface sheets from 0 to 10 GPa, whereas Y2InB has eight at ambient pressure, with no pressure-induced topological reconstruction. Charge-density and overlap analyses indicate mixed ionic-covalent Y-B bonding within a delocalized metallic background. Optical parameters are anisotropic. Unit-
cell phonon spectra contain positive frequencies at 0 and 10 GPa, although expanded-supercell calculations reveal low-frequency sensitivity. These results establish mechanically viable pressure windows and clarify substitution-driven structure-property relationships for these borides.
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All authors M. Rabi Us Sani Shapon, Md. Asif Afzal, Jubair Hossan Abir, Raihana Shams Islam, Saleh Hasan Naqib
Materials Science
Spiral Edge States in Topological 2D Sb2Te3 Crystals
Timothy Carlson, Daniel Lazega, Scott McGuire et al. (+7 more)
This work explores the edge state conduction properties of twinned and spiraled, 2D Sb2Te3 topological
insulator crystals. We show the structure supports spatially continuous edge states within two spiral and knotted edge conduction channels. The channels are connected through a topological defect. This geometry introduces boundary conditions into the 2D
crystal that modifies the edge state dispersion. Using a combination of low loss Electron Energy Loss Spectroscopy,
Magnetic Force Microscopy and traditional carrier transport measurements we identify a distinct excitation at 0.155 eV in the spiral that seems to be related to two isolated states within the gap. This state is localized to the
crystal edges. The modification of edge state bands using manipulation of a systems
quantum geometry may open new avenues for the use of 2D topological systems.
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All authors Timothy Carlson, Daniel Lazega, Scott McGuire, Mihirangi Medahinne, Motahhare Mirhosseini, Gabriel Marcus, ChaoChao Dun, Maria Kolesnik-Gray, Vojislav Krstic, David Carroll
Materials Science
Pressure-transferable universal machine-learning potentials: the WBM-MatPES benchmark and Tuga-FF
Pierre-Paul De Breuck, Thalis H. B. da Silva, Antoine Loew et al. (+2 more)
Universal machine-learning interatomic potentials hold the promise to replace costly ab initio calculations in materials science workflows. However, the accuracy and transferability of current models are limited by the availability of training data. We release WBM-MatPES, a
dataset of 182 thousand structures recomputed with consistent MatPES settings, together with two reference convex hulls of different depths and test sets at six pressures up to 150 GPa. These
datasets reproduce a realistic discovery workflow and allow potentials to be ranked systematically at this level of theory, similar to the Matbench Discovery leaderboard at the Materials Project settings. In this
benchmark, five published MatPES potentials agree within 12 meV/atom at 25 GPa, yet their errors increase dramatically to 0.4-5 eV/atom at 150 GPa. To address this limitation, we develop Tuga-FF, a graph
transformer trained on
datasets spanning ambient and high-pressure configurations alike. Tuga-FF is the most accurate model in the
benchmark at ambient pressure, with an energy error of 13.6 meV/atom, and maintains an error of just 21 meV/atom at 150 GPa. We believe this
benchmark will encourage the community to train higher-accuracy models and generate richer
datasets, advancing machine-learned interatomic potentials as a whole.
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All authors Pierre-Paul De Breuck, Thalis H. B. da Silva, Antoine Loew, Silvana Botti, Miguel A. L. Marques
Soft Condensed Matter
A Higher-Order Stroh Framework for Weakly Nonlinear Post-Bifurcation Analysis
Shiyuan Deng, Han Ye, Yafei Wang et al. (+8 more)
Linear stability analysis predicts the onset of wrinkling, while weakly nonlinear analysis determines whether the bifurcation is supercritical or subcritical through the sign of the cubic amplitude coefficient. When this coefficient vanishes, higher-order terms are needed. In this paper, we develop a higher-order Stroh framework for weakly nonlinear post-bifurcation analysis of finitely deformed elastic solids. For each nonzero harmonic, the same base-state Stroh operator is retained at every order, with nonlinear source terms assembled from lower-order fields to account for geometry, constitutive laws and constraints. This recursive structure, together with Fredholm solvability conditions, enables us to derive cubic, quintic and higher-order amplitude equations. Here, we demonstrate the power of this framework by analysing wrinkling in an incompressible neo-Hookean film bonded to an exponentially graded substrate. The results recover established linear instability
benchmarks and the supercritical-subcritical transition in the homogeneous-substrate limit. For graded substrates, the cubic coefficient vanishes on a surface in the parameter space of modulus ratio and substrate gradation. On this surface, the quintic coefficient takes both signs, corresponding to supercritical and subcritical bifurcations. These regions are separated by a curve along which the quintic coefficient also vanishes. Determining the branch direction along this curve requires higher-order terms, which can be calculated within the same framework.
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All authors Shiyuan Deng, Han Ye, Yafei Wang, Lizichen Chen, Alain Goriely, Yibin Fu, Weiqiu Chen, Chaofeng Lü, Michel Destrade, Kecheng Li, Yangkun Du
Strongly Correlated Electrons
Emergent one-dimensional Bloch oscillations in coupled Ising layers
E. S. Ma and Z. Song
Bloch oscillations typically arise in periodic systems subjected to a constant force generated by a potential gradient. Here, we study domain-wall dynamics in coupled Ising layers under asymmetric longitudinal fields. The interlayer coupling is of Heisenberg type and acts as an effective transverse coupling in the emergent pseudospin representation. We show that the rung pseudospin structure gives rise to kinetic constraints, restricting the many-body dynamics to an emergent one-dimensional quasiparticle subspace within the original two-dimensional system. Furthermore, the imbalance between the longitudinal fields of the two layers induces an effective linear potential for the emergent domain-wall excitations, leading to their confinement between two oppositely polarized ferromagnetic domains. Remarkably, the resulting Wannier–Stark ladder of domain-wall excitations gives rise to Bloch oscillations in the absence of a conventional tilted potential, revealing a distinct mechanism for coherent
quantum dynamics. Numerical simulations of time-dependent observables confirm the analytical predictions.
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Strongly Correlated Electrons · Cross-listed from math.QA
Lifts of symmetries to minimal nondegenerate extensions are unique up to fermion attachment
Ran Luo and Jiahua Tian
Gauging
fermion parity in a $(2+1)$-dimensional fermionic topological order requires lifting its
symmetries to the resulting bosonic theory. We give a direct tensor-categorical proof that, for a slightly degenerate braided fusion category $\mathcal{C}$ and a fixed minimal nondegenerate extension ${\cal E}$, the restriction homomorphism $r\colon\operatorname{Aut}_{\mathrm{LR}}(\mathcal{E})\to \operatorname{Aut}_{\mathrm{LR}}(\mathcal{C})$ on classes of complex-linear locality-respecting (LR) braided autoequivalences is surjective with central kernel $\mathbb{Z}/2$, generated by
fermion attachment. Thus each
symmetry class has exactly two LR lift classes, related by attaching the
fermion to every
vortex. We apply graded Morita theory to reduce the kernel to two module types on the
vortex sector, corresponding to tensoring with the
vacuum or the
fermion. We then prove relative rigidity to show that each type determines a unique LR class, which are distinguished by fermionic self-braiding even when their actions on simple-object labels coincide. We prove surjectivity by extending graph
algebras in $\mathcal{C}^{\mathrm{rev}}\boxtimes\mathcal{C}$ to Lagrangian
algebras in $\mathcal{E}^{\mathrm{rev}}\boxtimes\mathcal{E}$. Our results require neither unitarity nor a ribbon structure. We illustrate the lifting ambiguity in the Laughlin state, the $SO(3)_3$ theory and the Ising topological order.
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Materials Science
Selective faceting induced by Hexagonal Boron Nitride on curved Platinum substrate
Alaa Mohammed Idris Bakhit, Muhammad Saad Mahmood, Khadiza Ali et al. (+5 more)
This work combines experimental investigations and first-principles calculations to study hexagonal boron nitride (hBN) growth on a curved Pt(331) substrate. Low-energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) were employed to investigate the structural properties, observing that hBN growth led to faceting with several stable facets: Pt(111), Pt(221), Pt(441), Pt(881), and Pt(110). Additionally, the electronic properties were examined by X-ray photoemission spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS), revealing an increase in the hBN-substrate interaction strength, from the weakest at the Pt(111) to the strongest at the Pt(110). Density functional theory (DFT) calculations confirm that the selective faceting mechanism is induced by hBN, which changes the order of relative stability of the uncovered facets. Although a complete understanding of the process is not achievable using only thermodynamical arguments, the comparison between hBN adhesion energies and clean surface free energies clearly indicates that some facets are stabilized with respect to others by stronger overlayer-substrate interaction, whereas for others the clean surface energetics plays the dominant role.
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All authors Alaa Mohammed Idris Bakhit, Muhammad Saad Mahmood, Khadiza Ali, Anna A. Makarova, Igor Piš, Federica Bondino, Frederik Schiller, Maria Peressi
Soft Condensed Matter
Active remodeling rescues a microswimmer from geometric trapping
Ayushi Bhatt, Nico Schramma, Jasper van der Gucht et al. (+1 more)
Natural habitats confront microorganisms with heterogeneous, mechanically complex surroundings that shape how they move and explore. Most studies of motility in complex media treat the environment as either a homogeneous fluid or a rigid obstacle field. Here we instead study a medium that is simultaneously soft and reconfigurable — deformable by the organism moving through it. We track the unicellular biflagellate microalga Chlamydomonas reinhardtii swimming in a soft, disordered suspension of microgel particles comparable in size to the
cell itself, across a range of gel packing fractions. With increasing packing fraction, trajectories change from long straight runs to short, frequently reorienting ones, and the effective translational diffusivity decreases monotonically. The bimodal run/tumble speed distribution, characteristic of the free-swimming gait, collapses toward a single mode as the packing fraction increases, by near-proportional slowing of both gait states rather than a redistribution of
cells between them. Recasting trajectories as alternating hops and traps reveals the signature of a deformable medium: hop lengths halve as the gel densifies, approaching the microgel aggregate scale, while trapping times do not increase with increasing packing fraction. Independent force estimates place the
cell's propulsive force close to an order of magnitude above that needed to deform a single grain, so remodeling is expected rather than merely observed. A minimal active remodeler model — an active Brownian particle among mobile, rigid obstacles — shows that obstacle mobility alone is sufficient to relocate the onset of permanent trapping. Thus, our results establish obstacle mobility as a control parameter for motility in soft, disordered matter.
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All authors Ayushi Bhatt, Nico Schramma, Jasper van der Gucht, Uddalok Sen
Superconductivity
Driven Vortex Motion in Periodic Channel Potential Embedded in Superconducting Films
A. Al Luhaibi, A. Glatz, Michael Vogl et al. (+2 more)
In this paper, we investigate
vortex dynamics in periodically width-modulated superconducting channels by numerically solving the time-dependent Ginzburg-Landau (TDGL) equations. The channels are designed with sinusoidally varying widths characterized by their average width and modulation amplitude. The motion of driven
vortices generates an oscillatory electric field with a fundamental frequency, $f_0$, set by the channel periodicity, together with higher-order harmonics. In contrast to the situation of
vortex lattice dynamics in a periodic pinning landscape of circular holes considered by Al Luhaibi et al. [1], we show that the harmonic content of the generated electric field can be effectively controlled through the channel geometry. In particular, appropriately engineered channel profiles strongly suppress higher-order harmonics, yielding an electric-field response that closely approaches a pure sinusoidal waveform. These results demonstrate that
geometric modulation offers a viable route to engineering low-harmonicity microwave signals in superconducting devices and may enable cryogenic on-chip waveform generators for controlling superconducting
qubits. Such devices could provide a useful building block for scalable transmon-based
quantum computing architectures.
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All authors A. Al Luhaibi, A. Glatz, Michael Vogl, Hocine Bahlouli, J. B. Ketterson
Materials Science
Inverse Designing Reconfigurable Piezoelectric Tensors via Architectural and Modal Programming
Anish Satpati, Marco Maurizi, Hyunmoon Cho et al. (+3 more)
Piezoelectricity arises from the coupling between electric polarization and mechanical deformation, described by a third-rank tensor whose coefficients are constrained by
crystal symmetry. In natural
crystals, atomic periodicity and energetic stability restrict accessible
symmetries, limited to 20 distinct anisotropies that can exist. Here we establish a general framework, based on graph representation, for controlling the full effective piezoelectric tensor through architecture by resolving how macroscopic
symmetry, local polarization and deformation of structural elements act together. This enables each coefficient to be traced to the members that reinforce or cancel it and be controlled through targeted
geometric changes. We further uncover frequency-selective tensor reconfiguration, in which excitation frequency switches the dominant piezoelectric coefficients of a single architecture. These principles open a broader class of applications in which a single piezoelectric architecture can deliver programmable sensing, actuation and mode conversion across multiple directions and deformation states. We realize a multi-degree-of-freedom actuator that integrates distinct actuation modes in one block and reduces volume by 90% relative to conventional multi-stack assemblies.
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All authors Anish Satpati, Marco Maurizi, Hyunmoon Cho, Victor Couedel, Nicolas Mule, Xiaoyu Zheng
Superconductivity
Kink boundary-induced polarity revealed by nonreciprocal charge transport in FeTe0.7Se0.3 superconductor
Shengyao Li, Ya Deng, Han Yan et al. (+7 more)
Nonreciprocal charge transport, characterized by direction-dependent electrical response, provides a powerful probe of electronic structure and a platform for rectification. However, its realization is typically governed by intrinsic
crystal symmetry, restricting the range of suitable materials. Here, we demonstrate nonreciprocal charge transport in an otherwise centrosymmetric
superconductor, FeTe0.7Se0.3 (FTS), through kink boundary-induced strain engineering. The stress relaxation during growth generates a cusp-like kink-band boundary with asymmetric
curvature, producing a spatially nonuniform strain field and an effective in-plane polarity that breaks inversion
symmetry. Pronounced nonreciprocal transport is observed under out-of-plane
magnetic fields, with strong dependence on current and temperature across the superconducting transition, in contrast to the negligible response in flat nanosheets. Our results identify kink boundary-induced
symmetry breaking as a general route to engineer nonreciprocal charge transport in centrosymmetric systems.
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All authors Shengyao Li, Ya Deng, Han Yan, Dianyi Hu, Zherui Yang, Xueyan Wang, Ming Yue, Qiong Wu, Zheng Liu, X. Renshaw Wang
Materials Science
Finite-temperature adiabatic-connection reduced density-matrix functional theory: a unified framework for i-DMFT and TAO-DFT
Jingang Han, Huanjing Gong, Kai Luo et al. (+2 more)
Accurately describing chemical bond breaking requires capturing strong/static electron correlation, a major challenge for single-reference self-consistent-field methods such as Hartree–Fock and Kohn–Sham density-functional theory (DFT). Fractional occupations substantially improve this situation, as demonstrated by information-density-
matrix-functional theory (i-DMFT) and thermally-assisted-occupation DFT (TAO-DFT). Although useful, they are formulated within rather different theoretical frameworks, are somewhat semi-empirical, and their relationship remains unclear. Here we introduce finite-temperature adiabatic-connection reduced density-
matrix functional theory (FT-AC-RDMFT), in which i-DMFT and TAO-DFT emerge as different reductions of a unified framework. The effective
eigenvalue equation for natural orbitals and the Fermi–Dirac occupation numbers follow directly from the variational principle, while a thermal adiabatic connection relates the empirical
entropy coefficient of i-DMFT to a characteristic temperature of the auxiliary non-interacting system. Within this framework, i-DMFT is the exact-exchange-based reduction, whereas TAO-DFT results when exact exchange is replaced by a density-based exchange-correlation functional. Numerical calculations confirm that i-DMFT, apart from a constant, coincides with the exact-exchange realization of the framework, and show that the improved dissociation behavior from finite-temperature occupations extends beyond exact exchange to hybrid and semilocal density functionals. For strongly correlated V2O3, finite-temperature occupations substantially reduce the severely overestimated non-
magnetic LDA bulk modulus, bringing it close to experiment. These results establish FT-AC-RDMFT as a common theoretical foundation for finite-temperature occupation-based electronic-structure methods in molecular and solid-state systems.
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All authors Jingang Han, Huanjing Gong, Kai Luo, Hongming Weng, Xinguo Ren
Materials Science
Crossed Electric Spin Generation in Multilayers
Xukun Feng, Wei Du, Jin Cao et al. (+3 more)
We propose a crossed electric
spin generation effect in multilayer structures. This effect combines the advantages of in-plane and gate electric fields for manipulating
spin, and unveils a nice
quantum geometric structure in terms of the underlying hybrid Berry
curvatures that are unique to quasi-2D systems and manifest inherent
spin-layer-orbital coupling. Combining our theory with first-principles calculations, we predict sizable
spin generation in 2D ferromagnetic Fe3GeTe2 and altermagnetic V2Te2O. Our theory opens a new Berry-
curvature route for all-electric
spin manipulation in 2D materials
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All authors Xukun Feng, Wei Du, Jin Cao, Qian Niu, Shengyuan A. Yang, Cong Xiao
Mesoscale and Nanoscale Physics
Magnon Klein paradox
D. Wang
By considering the energy transport of
spin wave, we show that, like the electron Klein paradox, there is no
magnon Klein paradox for reflectivity. Heuristically, this can be understood according to the fact that, even if the ground state is unstable, any energy-carrying wave cannot have greater-than-one reflectivity off a passive interface, which will violate the conservation of energy. The
magnon Klein paradox discussed in the literature is derived from assigning a wrong sign to the transmitted
spin wave.
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Superconductivity
Chemical-Potential-Dependent Superconducting Spectroscopy on Bi2Te3/NbSe2 Heterostructures
Pengyu Hu, Chun Yu Wan, Qiaoyan Yu et al. (+21 more)
High-resolution scanning tunneling spectroscopy performed at dilution refrigerator temperatures was employed to investigate the superconducting properties of topological
insulator/
superconductor (Bi2Te3/NbSe2)
heterostructures. Coherence peaks with inner kinks or inner peaks, deviating from the conventional single s-wave spectral line shape, were observed in both 5 quintuple-layer (5QL) and 7QL Bi2Te3 thin films. Based on the combination of chemical-potential-dependent spectroscopic measurements and model simulations, we conclude that these spectral features arise from contributions of bulk and surface states in Bi2Te3 by selectively proximity-coupled to a single superconducting gap from NbSe2, rather than inheriting the complicated
superconductor's order parameter of NbSe2.
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All authors Pengyu Hu, Chun Yu Wan, Qiaoyan Yu, Chen Qian, Yisheng Gu, Xian Du, Xuhui Ning, Tingwen Miao, Shi Chen, Zihao Ma, Hao Yang, Hemian Yi, Weijiong Chen, Xiaoxue Liu, Liang Liu, Dandan Guan, Yaoyi Li, Shiyong Wang, Canhua Liu, Sangen Zhao, Fulin Wang, Junwei Liu, Hao Zheng, Jinfeng Jia
Materials Science
Enhancing Quasi-Two-Dimensional Electronic Structure in Bi2O2Se via Chlorine Substitution
Yong-Zhen Jiang, Qi-Xun Wen, Xiang Xu et al. (+17 more)
Bismuth oxyselenide (Bi2O2Se) has emerged as a leading
semiconductor candidate for next-generation electronics and
quantum phenomena research. However, its strong ionic interlayer bonding of Se layers fundamentally restricts the full potential of this otherwise promising quasi-two-dimensional (2D) material. In this work, we demonstrate chlorine substitution as an effective strategy to introduce van der Waals gaps and modify the electronic structure of the system. Through comprehensive transport and angle-resolved photoemission spectroscopy (ARPES) measurements on Bi6O6Se2Cl2 single
crystal, an optimal Cl-doping compound, we show that the key electronic features, including indirect band gap, high electron mobility, and carrier effective mass, are well preserved, while the 2D character of the system is sufficiently enhanced. First-principles calculations attribute this selective tunability to the unique spatial separation between conductive Bi-O layers and dopant Se/Cl layers, which enables independent optimization of interlayer coupling and intralayer transport. Remarkably, our theoretical calculations combined with experimental observations project a broad bandgap engineering across a wide range (0.8 ~ 3.5 eV) within the Bi2O2Se system. Our findings not only expand the application potential of Bi2O2Se-based materials in optoelectronics, nanoelectronics, and fundamental research but also highlight spatial decoupling as a viable strategy for modifying detailed electronic structure of quasi-2D
quantum systems.
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All authors Yong-Zhen Jiang, Qi-Xun Wen, Xiang Xu, Su-Tao Sun, Feng-Fan Ren, Zi-Xuan Zhou, Xing-Yuan You, Yu-Cheng Kan, Zheng Zhang, Jie-Yi Liu, Yu-Zhou Zhao, Zheng-Tai Liu, Mao Ye, Shu-Hua Yao, Jian Zhou, Yan-Bin Chen, Zhong-Kai Liu, Yu-Lin Chen, Yang-Yang Lv, Cheng Chen
Materials Science · Cross-listed from physics.optics
Maximal Axion Optical Chirality Enabled by Degenerate Quasibound States in the Continuum
Chang-Yin Ji, Chong Wang, Jiafang Li et al. (+1 more)
Axion quasiparticles introduce magnetoelectric coupling in topological materials, yet their optical signatures are intrinsically weak, severely limiting experimental detection and practical exploitation. Here, we demonstrate maximal optical chirality of
axion quasiparticles by coupling them with degenerate quasibound states in the continuum (qBICs). By integrating three-dimensional topological
insulators (3DTIs) with achiral photonic
crystal slabs (PCSs), we reveal that
axion quasiparticles induce an effective Zeeman effect that lifts the degeneracy of achiral qBICs in PCSs, splitting them into two nondegenerate high-Q chiral qBICs with maximally opposite chirality. These result in a more than 10^3- and 200-fold increase in the polarization conversion efficiency and Faraday rotation angle, respectively, compared to the intrinsic chiroptical response of bare 3DTI films. Moreover, circular dichroism and nonreciprocal optical responses are revealed as new key signatures for probing
axion quasiparticles in 3DTI-PCS coupled systems. Our results provide a definitive route for observing
axion quasiparticles and topological physics, while establishing a promising platform for controlling optical polarization,
spin, phase, and nonreciprocal responses.
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All authors Chang-Yin Ji, Chong Wang, Jiafang Li, Yugui Yao
Materials Science
A Fisher-Geometric Approach to Supercell Pair Distribution Function Refinement
Dawei Wang
Refining atomistic supercells against powder pair distribution functions (PDFs) requires optimizing many coupled atomic coordinates using a much smaller set of radial measurements. Reverse-mode differentiation makes gradients accessible for large systems, but standard first-order optimizers do not explicitly use coupled PDF sensitivities to precondition coordinate updates. We introduce a
matrix-free, Fisher-
geometric approach that pulls the information metric of the observation likelihood back onto atomic coordinates. The resulting update weights collective displacements according to their PDF response and experimental uncertainty. Under isotropic damping, the update is obtained by solving a damped linear system over $M$ PDF channels, using automatic differentiation to evaluate Jacobian–vector and vector–Jacobian products without constructing the full Jacobian or coordinate
curvature matrix. For Gaussian measurement errors, the update recovers classical Levenberg–Marquardt refinement while avoiding dense coordinate-space factorization. The same computational framework accommodates correlated Gaussian errors and robust likelihood-based updates. This approach combines likelihood-aware collective updates with
matrix-free backpropagation for direct second-order refinement of large atomistic supercells.
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Soft Condensed Matter
Surface Granular flows: Two Related Examples
Devang V. Khakhar and Ashish V. Orpe
Granular surface flows are common in industrial practice and natural systems, however, theoretical description of such flows is at present incomplete. Two prototype systems involving surface flow are compared: heap formation by pouring at a point and rotating cylinders. Continuum models for analysis of these flows are reviewed, and experimental results for quasi-2d systems are presented. Experimental results in both systems are well described by continuum models.
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Soft Condensed Matter
Optoelectronically Enabled Simultaneous and Decoupled Navigation and Selective Pairing of Electrically Driven Janus Particles for Multi-Agent Microrobotics
Srikanta Debata, Ido Rachbuch and Gilad Yossifon
Self-propelled Janus particles are promising active
agents for microscale manipulation and microrobotic applications. However, when powered by a global external energy source, such as an electric,
magnetic, or optical field, all particles respond simultaneously, preventing their independent and concurrent control. Achieving parallel, decoupled control without continuous particle-specific feedback, while preserving intrinsic self-propulsion, remains a significant challenge. Here, we present an optoelectronic (OE) strategy for simultaneously and independently controlling electrically driven, self-propelled metallo-dielectric Janus particles (JPs) using spatially programmable virtual electrodes. These electrodes are generated by projecting a single predefined illumination pattern from a digital micromirror device onto a photoconductive surface. The resulting confinement landscape enables multiple JPs to follow distinct trajectories without continuous monitoring, feedback, or pattern reconfiguration. We demonstrate controlled pairing of JPs with passive polystyrene particles and biological
cells. For automated multi-
agent operation, an image-based assignment framework identifies optimal
agent-target pairs, excludes intersecting trajectories, and generates a single composite pattern for simultaneous, selective pair formation without real-time updating. Finally, we demonstrate independent manipulation of multiple magnetically rolling JPs under a globally applied
magnetic field. Overall, this programmable open-loop strategy provides a versatile framework for multi-
agent microrobotic manipulation, with potential applications in in-vitro micromanipulation and microfluidic systems.
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