Mesoscale and Nanoscale Physics
Band's Geometry Origin of Quantum Spin Transport Phenomena
Elena Derunova and Mazhar N. Ali
We develop a
geometric description of
spin-dependent transport based on the local
geometric structure of electronic bands and the Fermi surfaces. For quasi-two-dimensional systems, we show that
hyperbolic regions of constant-energy surfaces generate a geometrical contribution to the Fermi velocity that couples naturally to electron
spin and produces a
spin-current response. We further show that, in the presence of time-reversal
symmetry, the
algebra of
spin operators can be related to the exterior
algebra of the band's tangent space, providing an additional
geometric interpretation of
spin in momentum space. This framework motivates a symplectic description of
spin-separated transport on Fermi surfaces and its extension to three-dimensional band
manifolds through contact geometry. Our results establish a direct connection between Fermi-surface geometry and intrinsic
spin transport.
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Mesoscale and Nanoscale Physics
Trapping $e/4$ quasiparticles in bilayer graphene
Mario Di Luca, Emily Hajigeorgiou, Ning Ma et al. (+4 more)
Measuring the charge of the quasiparticles hosted by even-denominator fractional
quantum Hall (FQH) states is essential to identify the
topology of their ground state. Here, we use a gate-defined antidot in bilayer
graphene, with an additional gate to control only the antidot potential, to measure the charge of the quasiparticles trapped around it in even-denominator FQH states. We observe a localized charge of $e/4$ at $\nu=-5/2$, $-1/2$, and $3/2$, consistent with the minimal excitation expected for leading candidate even-denominator ground states, and $e/3$ at the hole-conjugate state $\nu=2/3$. We further show that increasing the coupling between the antidot-bound states and extended edge states drives a crossover between two regimes, characterized by the minimal-excitation gate-voltage period and approximately twice that period, respectively. We discuss two possible explanations for this crossover: quasiparticle bunching and a crossover between distinct antidot transport regimes. Our results, together with previous observations of the daughter states, show that the even-denominator FQH states in bilayer
graphene are compatible with a non-Abelian ground state, and that their quasiparticles can be localized around a
quantum Hall antidot, a necessary ingredient for topological
quantum computation.
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All authors Mario Di Luca, Emily Hajigeorgiou, Ning Ma, Alexandra Waldherr, Kenji Watanabe, Takashi Taniguchi, Mitali Banerjee
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Ratul Thakur and Sthitadhi Roy
The physics of information scrambling in
quantum many-body systems is intimately related to thermalisation and emergence of chaos. However, its standard characterisation through bipartite
entanglement or operator growth remains inherently coarse-grained, obscuring the spatiotemporal anatomy of how
quantum information flows between different regions of the system and across various length scales. In this work, we develop a theory for the dynamics of local information in local random
unitary circuits which resolves the fine-grained microscopic structures of local information flow in such systems. Using the framework of information
lattice which systematises the information content at each length scale within each subsystem, we identify a distribution of length scales at which information resides and obtain the dynamics of the distribution. For Haar-random
circuits with infinite local
Hilbert-space dimensions, we map this dynamics onto an exact classical
stochastic process which reveals that this distribution is described by a Tracy-Widom form which moves ballistically in time ($ \propto t$) toward larger scales, accompanied by a $\sim t^{1/3}$ broadening. We also find the same qualitative behaviour for random Clifford
circuits acting on
qubits. The similar scaling behaviour in two rather different settings hints strongly towards the universality of our results. In the case of Clifford
circuits, we develop a phenomenological Markov process for the dynamics of the stabiliser generators in a specific gauge which confirms the Tracy-Widom distribution and the $t^{1/3}$ scaling of the fluctuations. Ultimately, our results establish the universal properties of the dynamics of local
quantum information in a length scale-resolved fashion and provide a possible route towards bridging exact microscopic theories for information dynamics with emergent hydrodynamic descriptions of information flow.
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Quantum Gases · Cross-listed from quant-ph
Detuning- and Stark-robust Rydberg gates
Elie Bataille, Gyohei Nomura and Manuel Endres
Rydberg entangling gates driven by a two-
photon transition in alkali atoms suffer from an adverse scaling of light-shift-induced errors. Robustness to such detuning errors is known to be impossible to achieve in the design of conventional Rydberg gate protocols, where only one of the
qubit states is coupled to the Rydberg state. Here, we show that in a more general framework, in which both
qubit states take part in the gate, full or partial robustness to these errors can be realized. We present two gate constructions, which either cancel the errors outright or convert them into single-
qubit errors that can be corrected locally. We map the regimes – in terms of light-shift strength, intensity inhomogeneity, and Rydberg decay rate – in which these protocols outperform the widely used time-optimal Rydberg gate, and find that they already include the conditions of state-of-the-art experiments. Finally, we show the existence of a Rydberg `fly-by' entangling gate, an important primitive for an emerging class of neutral-atom
quantum computing architectures.
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Strongly Correlated Electrons
A continuous confinement-deconfinement transition in a triangular quantum magnet
Suguru Hosoi, Sejun Park, Michihiro Hirata et al. (+13 more)
A continuous transition between phases hosting distinct excitations—bosonic
magnons versus fermionic spinons—is a long-sought phenomenon in
quantum magnetism, analogous to the confinement–deconfinement transition in
quantum chromodynamics. We report evidence for such a transition in the triangular-
lattice antiferromagnet TlYbS$_2$. Antiferromagnetic order develops below $T_\mathrm{N} \approx 0.53\,\mathrm{K}$. A $c$-axis field suppresses this order, driving the system into a gapless
quantum spin liquid with a spinon Fermi surface above $\mu_0 H_\mathrm{c} \approx 3\,\mathrm{T}$, evidenced by a finite residual linear term in thermal conductivity, a Pauli-like susceptibility, and a temperature-independent NMR Knight shift. Approaching $H_\mathrm{c}$ from above, the scattering rate of itinerant excitations is strongly enhanced while their density of states shows no critical enhancement, atypical of conventional
magnetic quantum criticality. These results point to a continuous confinement–deconfinement transition governed by fractionalized excitations beyond the Ginzburg–Landau paradigm.
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All authors Suguru Hosoi, Sejun Park, Michihiro Hirata, Minseong Lee, Adam P Dioguardi, Joe D Thompson, Filip Ronning, Allen O Scheie, Kumpei Imamura, Kenichiro Hashimoto, Takasada Shibauchi, Bishnu P Belbase, Arjun Unnikrishnan, Johannes Knolle, Arnab Banerjee, Yuji Matsuda
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Krylov Break Times from an Inhomogeneous Lieb–Robinson Light Cone
Shunji Matsuura, Yoji Kawamura, Joseph Salfi et al. (+1 more)
Krylov and Lanczos approximations are used in
quantum dynamics,
quantum subspace methods, and
Hamiltonian learning. A practical question is how long an $m$-dimensional Krylov truncation can be trusted. We argue that this time is fixed by causal propagation on the associated Jacobi chain. The relevant distance is not the Krylov index itself, but the inhomogeneous transport metric $\rho(m,n) = \sum_{j=\min(m,n)}^{\max(m,n)-1} 1/b_j$, where $b_j$ is the Lanczos hopping across the bond $j \leftrightarrow j+1$. We prove a Lieb–Robinson bound in this metric. Its small-weight limit gives the velocity $v_{\rm LR} = 2$, meaning that propagation is exponentially suppressed outside the cone $\rho(m,n) \simeq 2|t|$. The error of a finite Krylov approximation to the return amplitude is a round-trip effect: information has to travel from the probe to the truncation boundary and back. Combining the Lieb–Robinson bound with Duhamel's formula yields a lower bound on the error of the truncated dynamics. For a fixed tolerance $\epsilon$, let the break time $t_\ast(m;\epsilon)$ denote the longest time for which the $m$-dimensional truncation is guaranteed to reproduce the exact return amplitude within error $\epsilon$. We show that $t_\ast(m;\epsilon) \ge \tau_m[1-o(1)]$, where $\tau_m = \rho(0,m) = \sum_{j<m} 1/b_j$. When the probe spreads along the chain, this lower bound is also tight, so $t_\ast(m) \simeq \tau_m$. The situation is different when the probe excites only a localized part of the spectrum, or a part already resolved by the truncation. In this case, essentially no signal reaches the boundary. Beyond a state-dependent Krylov dimension $m_\ast$, the approximation can therefore remain accurate at all times, and the break time is effectively infinite. Numerical tests on
spin chains and random Jacobi
matrices support $t_\ast(m) \simeq \tau_m$ in the transport-limited regime.
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All authors Shunji Matsuura, Yoji Kawamura, Joseph Salfi, Satoshi Iso
Quantum Gases · Cross-listed from quant-ph
Stochastic transport of a Goldstone mode in a self-organized atomic crystal
Zhanhai Yu, Di Xiang, Xiaotian Zhang et al. (+1 more)
Spontaneous breaking of a continuous
symmetry produces a massless Goldstone mode that can evolve across a degenerate
manifold at zero energy cost. Goldstone modes have been identified primarily through excitation spectra, mode softening or collective oscillations. However, their time-domain transport under intrinsic fluctuations and dissipation has remained largely unexplored. Here we directly track the
stochastic transport of a Goldstone mode in a self-organized atomic
crystal inside an optical ring cavity. The ring cavity maps the order-parameter phase onto the real-space position of the emergent
crystal. Without any external perturbation, fundamental
photon-scattering recoil drives the collective transport, while cavity dissipation generates friction. We monitor individual trajectories of the atoms and their self-generated optical
lattice by measuring the cavity output phase. We find that the
diffusion constant decreases as $1/N$, indicating that all atoms move collectively as a rigid object rather than independently. By tuning the Langevin driving force and cavity-mediated damping, we show that the normalized
diffusion constant collapses onto a single universal curve. This work extends the study of continuous
symmetry breaking from excitation-frequency measurements to real-time tracking of transport, and opens routes for studying non-
equilibrium collective transport,
phonon dynamics, and defect formation in driven-dissipative
quantum matter.
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All authors Zhanhai Yu, Di Xiang, Xiaotian Zhang, Hao Zhang
Mesoscale and Nanoscale Physics
Scalable, Simple, and Versatile Encapsulation of 2D Materials and Devices
Gabriel Natale, Uma Chirkova, Flávio Henriques Feres et al. (+16 more)
Air-sensitive 2D materials present a fundamental challenge for device integration. Encapsulation is often required to preserve intrinsic properties, yet conventional protection strategies often fail for thicker layers and complicate fabrication. Here, we demonstrate that electron-beam (e-beam) evaporated aluminum oxide ($\mathrm{AlO}_x$) serves as both an effective encapsulation layer and a platform for direct device fabrication. Unlike transfer-based approaches, this scalable method is compatible with thicker flakes and full device or wafer coverage. It requires no stacking procedures and enables contacts without post-encapsulation etching. Using rare-earth tritellurides ($\mathrm{RTe}_3$, R = La, Er), semimetallic $\mathrm{WTe}_2$, and superconducting $\mathrm{FeTe}_x\mathrm{Se}_{1-x}$, we show that $\mathrm{AlO}_x$ suppresses oxidation and preserves intrinsic optical and electronic properties. We establish substrate-dependent optimization of encapsulation across a range of flake thicknesses, demonstrate that ultrathin $\mathrm{AlO}_x$ preserves $\mathrm{WTe}_2$'s plasmonic response and maintains superconducting performance in $\mathrm{FeTe}_x\mathrm{Se}_{1-x}$. Thus we overcome the longstanding tradeoff between encapsulation and straightforward device fabrication in fragile
quantum materials.
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All authors Gabriel Natale, Uma Chirkova, Flávio Henriques Feres, Ran Jing, Michael Geiwitz, Wenyao Liu, Emma Low, Josh Leeman, Kyung-Mo Kim, Leslie M. Schoop, Mohamed Shehabeldin, Qiong Ma, Michael A. Susner, Pijush Bhattacharya, Genda Gu, Katherine Lee, James Hone, Mengkun Liu, Kenneth S. Burch
Mesoscale and Nanoscale Physics
Mobility Enhancement in Si/SiGe Quantum Well Enabled by a Buried Si Layer Trapping Oxygen Impurities
Felix Reichmann, Alberto Mistroni, Fabian Fidorra et al. (+4 more)
Reducing disorder in undoped Si/SiGe field-effect
heterostructures remains an important materials challenge for scalable
quantum devices, particularly electron
spin qubits. Background impurities such as oxygen have been identified as mobility-limiting, yet practical
heterostructure-design strategies for suppressing their incorporation remain underexplored, and their influence across different transport regimes is not fully established. Here, we demonstrate a simple route to oxygen reduction and mobility enhancement in Si/SiGe
quantum-well
heterostructures grown by reduced-pressure chemical vapor deposition (RP-CVD) on 200 mm Si(100) substrates through the introduction of a thin, electrically passive buried Si layer within the lower SiGe barrier. Secondary-ion mass spectrometry shows that the buried Si layer reproducibly reduces the oxygen background in the subsequently grown SiGe by approximately a factor of five, without modifying the active
quantum-well region. Density- and temperature-dependent magnetotransport measurements further show that this reduction increases the electron mobility, while leaving the percolation density and density-dependent mobility scaling largely unchanged. Upon cooling to 0.3 K, both high- and low-oxygen devices exhibit similar density-dependent fractional mobility enhancements, indicating that the reduced oxygen background improves momentum relaxation without substantially altering the dominant low-density disorder landscape. These results establish the buried Si layer as a straightforward and process-compatible
heterostructure-design element for reducing oxygen incorporation and improving transport in 200 mm CVD-grown Si/SiGe
quantum-device materials.
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All authors Felix Reichmann, Alberto Mistroni, Fabian Fidorra, Giovanni Capellini, Yuji Yamamoto, Marco Lisker, Marvin H. Zoellner
Disordered Systems and Neural Networks · Cross-listed from math.PR
Universality and sharp thresholds for ellipsoid fitting
Frederic Koehler and Youngtak Sohn
We establish a sharp phase transition for fitting random vectors by an ellipsoid. The random vectors have independent subgaussian coordinates with mean zero, variance one, and a common fourth moment, and the number of vectors is proportional to the square of the dimension. We identify an explicit satisfiability threshold such that, with high probability, a positive definite ellipsoid passes through every data point below the threshold, whereas no positive semidefinite fit exists above it. We also determine the optimal squared fitting error throughout the unsatisfiable regime. In particular, the threshold depends on the coordinate distributions only through their common fourth moment, revealing a fourth moment universality phenomenon. For standard Gaussian data the threshold is $1/4$, resolving the ellipsoid fitting
conjecture.
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Materials Science
Temperature dependence of the charge density from first principles: application to the (222) forbidden reflection in silicon
Jean Paul Nery, Raveena Gupta, Olle Hellman et al. (+2 more)
Forbidden reflections (FRs) in X-ray diffraction have inherently weak intensity and have long been studied, in particular in
semiconductors like silicon. They serve as sensitive probes of
symmetry breaking, local strain, impurities, and weak charge redistribution. Despite extensive experimental work, the theory of their temperature dependence has typically relied on simplified models. While atomic Debye-Waller factors work well on allowed reflections, their applicability to the valence charge between atoms, which determines the intensity of FRs such as Si (222), is questionable, and previous agreement between theory and experiment relied on ad-hoc Debye-Waller corrections. We compute the temperature-dependent valence charge density $\rho(\mathbf{r},T)$ of silicon from first principles, using two methods: (i) perturbation theory, and (ii) averaging over thermally distorted supercells in a non-perturbative approach. The perturbative expression for the charge density is far more demanding than that for electronic energies, since it depends on the wavefunctions themselves and requires an explicit sum over unoccupied bands. We use an acoustic sum rule to express the second derivatives of the potential in terms of first derivatives, making the expression tractable within existing frameworks. The (222) FR then follows directly from the
Fourier transform of $\rho(\mathbf{r},T)$, with no ad-hoc factors. Both methods give similar results, in reasonable agreement with experiment, with thermal expansion noticeably affecting the temperature dependence. The charge density answers a question the measured intensities could not settle: how the valence charge actually redistributes with temperature. Relative to the rigid model, we find more charge in the bonds and less in the core regions, a redistribution that shows up in the intensity as a somewhat weaker temperature dependence of the (222) FR.
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All authors Jean Paul Nery, Raveena Gupta, Olle Hellman, Philip B. Allen, Matthieu J. Verstraete
Statistical Mechanics · Cross-listed from physics.flu-dyn
Dynamical slowdown, bottlenecks, and multiscaling in Voigt-regularised turbulence
Anikat Kankaria, Bikram Pal, Edriss S. Titi et al. (+1 more)
We investigate bottleneck formation in
turbulence using the Voigt-regularised SABRA model and DNS of the corresponding Voigt-Navier-Stokes (NSV) equations. The Voigt regularisation introduces a scale-dependent slowdown of nonlinear interactions without enhancing dissipation, providing a natural setting to study the interplay between nonlinear transfer and thermalised behaviour. We find three distinct spectral regimes: an inertial range at $k<k_I$, an intermediate
equilibrium-like range associated with partial thermalisation for $k_I<k<k_{II}$, and a high-$k$ thermal regime for $k>k_{II}$, where the Voigt contribution dominates the conserved invariant. The crossover to the high-$k$ regime occurs at $k_{II}\sim 1/\alpha$, while $k_I$ marks the onset of thermalised behaviour. Equal and multi-time statistics reveal a progressive suppression of intermittency and a tendency towards Gaussianity at small scales, together with a transition from dynamic multiscaling in the turbulent regime to simple scaling in the
equilibrium ranges. The shell model resolves these three regimes over a broad range of scales, while DNS of the corresponding NSV equations reproduces the same qualitative trends, including bottleneck formation, delayed cascade completion, reduced intermittency, and a tendency towards Gaussianity at small scales. We find that bottleneck formation might be associated with scale-dependent dynamical slowdown and incipient thermalisation, rather than being purely dissipative in origin. We provide strong evidence that, in the regime where the regularization parameter $\alpha$ is much smaller than the dissipation length scale, the Voigt model reproduces the same inertial-range turbulent regime and
turbulence statistics as the Navier-Stokes (NS) equations. This provides evidence that the Voigt model constitutes an excellent practical approximation to the NS equations for small $\alpha$.
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All authors Anikat Kankaria, Bikram Pal, Edriss S. Titi, Samriddhi Sankar Ray
Soft Condensed Matter
Nonparametric multiscale modeling of boundary lubrication: hexadecane in highly pressurized gold asperity contacts
Hannes Holey, Michael Moseler, Peter Gumbsch et al. (+1 more)
Boundary lubrication is governed by molecular processes at the sliding interface that are inaccessible to classical continuum descriptions. While molecular dynamics (MD) simulations can resolve these processes in atomistic detail, incorporating their output into engineering-scale models through semi-empirical constitutive laws becomes increasingly difficult as confinement approaches the molecular scale. Here, we apply a nonparametric multiscale framework based on Gaussian process (GP) regression to model boundary lubrication of hexadecane confined between gold surfaces under pressures up to 1 GPa and gap heights down to 1.4 nm. The GP surrogates are trained on nonequilibrium MD simulations of the confined fluid and directly provide stress predictions to a continuum thin-film solver, circumventing the need for fixed-form constitutive laws. The framework naturally captures molecular phenomena such as density layering, viscosity changes, and the strongly nonlinear wall slip that dominates the frictional response at high pressures and small gap heights. Our results reproduce the atomistic
benchmark data of Codrignani et al., demonstrating that nonparametric surrogate models offer a flexible and physically transparent route toward predictive continuum modeling of boundary lubrication.
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All authors Hannes Holey, Michael Moseler, Peter Gumbsch, Lars Pastewka
Superconductivity
High-Temperature Superconductivity of the Fe-Se-H compound
S.I. Bondarenko, A.A. Prokhorov, N.N. Galtsov et al. (+4 more)
Using an EPR spectrometer, the dependences of microwave power absorption on
magnetic field up to 6000 Oe were measured at temperatures of 3.6-25 K and 295 K in a powdered compound Fe-Se-H, obtained by thermal
diffusion of hydrogen into a FeSe single
crystal with a critical temperature of 8 K. The shape of the dependences and the analysis of the measurement results confirm the superconductivity of the Fe-Se-H compound at normal pressure, both at temperatures of 3.6-25 K and at 295 K, i.e., at room temperature.
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All authors S.I. Bondarenko, A.A. Prokhorov, N.N. Galtsov, V.P. Timofeev, V.P. Koverya, I.S. Bondarenko, A.V. Krevsun
Materials Science
Coupled anisotropic weak topological states and Floquet mixed-parity altermagnetism in two-dimensional Su-Schrieffer-Heeger models
Kunyuan Feng, Xibin Liu, Chenchen Liu et al. (+5 more)
Su-Schrieffer-Heeger (SSH) topological systems and altermagnetic (AM) states are two important research areas in condensed matter physics. Realizing the coupled states between the SSH
lattices and AM phanse in a single syetem remains challenging. However, the Floquet engineering change it. Our work constructs five two-dimensional-(2D-) SSH models to describe the coupled phases of SSH weak topological state and AM order by tight-binding (TB) method. The
evolution of band structures,
spin-splitting, and topological phase transitions under the circularly polarized light (CPL) and relative atomic displacement (RAD) in 2D SSH
lattices were systematically investigated. The results reveal that the inequality of hopping parameters (t1 and t2) serves as the fundamental origin of SSH topological states and AM order. For the 2D nonmagnetic state, anisotropic weak topological states with Zak phase governed edge states are realized by unit
cell selection, similar to the conventional 1D SSH model. The collinear antiferromagnetic state preserves the
spin-degenerate band structure and intrinsic weak topological properties. Furthermore, the Floquet engineering introduces the AM phase of odd-parity p-wave while the RAD introduces the AM phase of even-parity d-wave. By combining the two effects, the mixed-parity (non-odd/non-even parity) AM phase could be realized, achieving the simultaneous control of the light field of
spin-splitting and topological edge states. The physical mechanisms of Floquet engineering and RAD for the 2D rectangular SSH
lattice are also from the inequality of t1 and t2, which can be not only fully understand by the TB methods, but also in good agreement with the first-principle calculations of 2D carbon-based materials. This work establishes an effective theoretical platform for coupling anisotropic SSH weak topological states and AM orders with multi-parities in 2D systems.
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All authors Kunyuan Feng, Xibin Liu, Chenchen Liu, Siyuan Liu, Lixiu Guan, Xiaobiao Liu, François M. Peeters, Linyang Li
Quantum Gases
The heavy Fermi polaron I: the Lithium-Cesium experiment
Michael Rautenberg, Tobias Krom, Eleonora Lippi et al. (+2 more)
We present details of an experimental platform for studying Fermi polarons in a
quantum-gas mixture. The system consists of about a thousand bosonic $^{133}$Cs impurities immersed in a deeply degenerate Fermi gas ($T/T_F \sim 0.2$) of approximately $2\times 10^5$ $^6$Li atoms in a single hyperfine state, with interspecies interactions tunable via a Feshbach resonance. Using optical Raman spectroscopy without relative momentum transfer, we perform injection spectroscopy and thereby create the Fermi polaron. Owing to the large mass imbalance between the two species, the setup provides access to previously unexplored regimes of Fermi polarons.
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All authors Michael Rautenberg, Tobias Krom, Eleonora Lippi, Lauriane Chomaz, Matthias Weidemüller
Materials Science
Grain Boundary Phase Transitions Enable Diffusionless Climb of Disconnections
Md Sharier Nazim, Giacomo Po and Nikhil Chandra Admal
Dislocation-grain boundary (GB) interactions govern the mechanical response of polycrystalline materials by controlling dislocation absorption, transmission, and interfacial plasticity. While disconnection climb is conventionally understood to require the absorption or emission of point defects supplied through long range bulk
diffusion, GBs possess intrinsic configurational degrees of freedom associated with their atomic structure, or microstate, that may provide an alternative mechanism. Here, using bicrystallography and molecular dynamics simulations, we investigate the interaction of shear dislocation loops with the [1 1 0](-5 5 14) symmetric tilt grain boundary in Al. We show that dislocation absorption generates a mobile extrinsic disconnection with a nonzero climb component that propagates conservatively along the interface without long-range bulk point-defect transport. Its motion is accompanied by a localized GB phase transformation mediated by cooperative atomic rearrangements within the GB core, producing successive metastable GB microstates. These findings establish a direct coupling between
lattice dislocations and GB phase
evolution and reveal a conservative mechanism for disconnection climb fundamentally distinct from conventional vacancy-mediated climb.
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Materials Science
3D Cloud Component Analysis of Atomic Structures
Pai Li
We present a method for decomposing atomic structures into physically meaningful components by converting discrete atomic coordinates into continuous three-dimensional density fields. Each element is represented by a Gaussian-smeared density map with values ranging from 0 to 1, computed efficiently through a bin-then-blur approach with periodic boundary conditions. The sum of all element densities, truncated at unity, defines the material region; its complement defines the
vacuum. Every voxel is first assigned a chemical formula from the set of elements present above a threshold; the resulting formula map is then cleaned so that only regions with a genuine bulk interior-measured by the Euclidean distance to their own boundary-survive as components. Thin surface terminations (e.g., a Ga monolayer on GaAs) and one-to-two-voxel boundary layers between two
crystals are absorbed by the neighboring stable region, so the decomposition contains exactly the bulk-like chemical-formula components and the
vacuum, with no surface or interface components. For each component we determine the
crystal phase with a neural prototype classifier: one phase if the trusted interior atoms vote unanimously, two phases (e.g., crystalline and amorphous Si) if they split into two confident groups, in which case the component is divided into two. Interfaces and surfaces are then derived as boundaries-material-material and material-
vacuum-and every atom is labeled bulk, surface, interface, or vertex, with vertex reserved for
geometric corners of a component. Inside crystalline components, inner defects are detected from coordination-number and local-density deviations. We demonstrate the approach on Si/GaAs and Si/SiO2 heterojunctions, crystalline/amorphous silicon junctions, vacancy-containing
crystals, and bulk
crystals.
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Materials Science
Benchmarking of Fast and Interpretable UF Machine Learning Potentials
Pawan Prakash, Sam Dong and Richard G. Hennig
Machine learning interatomic potentials (MLIPs) have emerged as a powerful alternative to density functional theory (DFT) for molecular dynamics simulations, offering near-DFT accuracy at a fraction of the computational cost. However, many state-of-the-art MLIPs remain computationally demanding and act as black boxes, limiting physical interpretability. In this work, we evaluate the ultra-fast force field (UF$^3$) potential, which employs linear regression with cubic B-spline basis to represent effective two- and three-body interactions. We show that UF$^3$ displays accuracy comparable to established models such as GAP, MTP, NNP (Behler Parrinello), and qSNAP MLIPs. We further investigate the transferability of UF$^3$ by computing melting points for six elemental systems with potentials fitted without any solid-
liquid interface configurations or explicit thermodynamic information about melting. The model reproduces experimental melting points within $\sim$6% for simple metals (Ni, Cu, Li), but substantially underestimates them for Mo and Si and fails to yield a stable potential for Ge, reflecting the limitations of a fixed expansion truncated at the three-body term for systems with strong angular or covalent bonding. We further illustrate how UF$^3$'s spline-based formulation allows direct visualization of the learned interactions, enabling identification of unphysical behavior that black-box approaches often obscure.
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Materials Science
Grain-Boundary Premelting in High-Entropy Transition Metal Carbides
Marium M. Mou, Caleb Schenck, Samuel E. Daigle et al. (+4 more)
Grain-boundary segregation and thermally induced interfacial disordering were investigated in four high-
entropy transition metal carbides using Monte Carlo (MC) sampling and molecular dynamics (MD) with the universal MACE-OMAT-0 machine-learning interatomic potential. MC sampling segregated the group-VI element (Cr, Mo, or W) and Zr to grain boundaries, where the group-VI content reached approximately 45 at.%, consistent with STEM-EDS observations. During MD heating, the grain-boundary Lindemann index, a normalized measure of interatomic distance fluctuations, reached the
liquid-like threshold of $\delta=0.15$ near $1390^{\circ}\mathrm{C}$ for the Cr-containing carbides, $1660^{\circ}\mathrm{C}$ for Mo, and $1890^{\circ}\mathrm{C}$ for W, while the grain interiors remained below the threshold. A chemically random (Cr,Hf,Ta,Ti,Zr)C reference crossed about $60^{\circ}\mathrm{C}$ later and showed less boundary-localized disorder, highlighting the role of interfacial chemistry in premelting. Species-resolved displacements showed enhanced grain-boundary mobility, particularly for carbon. Overall, Cr-rich interfaces showed the earliest and most extensive premelting-like response, followed by Mo- and W-containing boundaries.
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All authors Marium M. Mou, Caleb Schenck, Samuel E. Daigle, William G. Fahrenholtz, Bharat Gwalani, Stefano Curtarolo, Donald W. Brenner
Materials Science
Crystal Structure Prototype Identification via Element-Mapped Rotation-Invariant Descriptors
Pai Li
We present a method for identifying
crystal structure prototypes from local atomic environments. A center atom and its neighbors within a distance-normalized cutoff are mapped to anonymous element types (A/B/C/D) by proximity, and a NEP-style descriptor-radial Chebyshev moments plus contracted spherical-harmonic (S-vector) invariants-is computed per type block. The descriptor is rotation-invariant by construction (MLFF-style contraction with analytic normalization constants), so no rotation augmentation is needed. A trainable block-diagonal projection compresses the 316-dimensional raw basis into a 168-dimensional learned descriptor fed to a three-layer MLP. The model classifies each atom into one of 271 AFLOW
crystal structure prototypes or the amorphous class (272 classes), reaching 99.38% accuracy on 538,190 per-atom samples. The full pipeline (descriptor extraction + inference) runs on a single CPU core at 3.9 s per 10,000 atoms, making it suitable for website deployment.
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Soft Condensed Matter
Asymmetric Ions in Solution are Similar to Active Brownian Particles
Setare Mostajabi Sarhangi and Dmitry V. Matyushov
Molecular dynamics simulations of electrolyte ions with charge shifted by the distance $d$ from the ion geometrical center have shown that mechanical
equilibrium in the ion's body frame is not established beyond a critical shift distance $d^*$. A sharp crossover to a non-zero body-frame force occurs due to frustration of water molecules failing to compensate the electrostatic pull with a local density augmentation. A solution ion with asymmetric charge experiences a net body-frame force similar to self-propelled motion of active-matter Brownian particles. Thermal
equilibrium and zero laboratory-frame force are still maintained, but the
diffusion constant drops significantly ($\sim 400$ times) when the charge displacement crosses the threshold value $d^*$. Alternative routes to the
diffusion constant become inequivalent and the
diffusion constant from the mean-squared displacement is much higher than those from velocity and force correlation functions.
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Statistical Mechanics
Long-time Dynamics of Many-body Open Quantum Systems using Quantum Generating Functions
Katha Ganguly, Dario Poletti and Bijay Kumar Agarwalla
The interplay between coherent
unitary evolution and environment-induced dissipation can give rise to a wide range of non-
equilibrium dynamics in open
quantum systems, ranging from interesting transport phenomena to dynamical phase transitions. However, accessing such long-time dynamics remains challenging for the existing methods developed for the simulation of many-body open
quantum systems. We address this problem by developing a
quantum generating function (QGF) formalism for open many-body systems for both ensemble-averaged dynamics governed by a Markovian
quantum master equation and trajectory-resolved dynamics described by the
quantum trajectory formalism, including
quantum jumps, and
quantum state
diffusion. Our approach computes the dynamics of higher-order moments and fluctuation statistics without explicitly evolving the
quantum state, thereby providing an efficient and scalable approach for investigating many-body open
quantum systems. We demonstrate the versatility of the formalism by applying it to both the integrable open XXZ chain and the nonintegrable open next-nearest-neighbor XXZ
spin chain, where it uncovers distinct initial state dependent long-time transport regimes. Our work establishes
quantum generating functions as an efficient and scalable framework for investigating long-time dynamics in open
quantum many-body systems.
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Strongly Correlated Electrons · Cross-listed from math-ph
2-Morita Theory of $E_2$-Algebras and Module Categories
Rongge Xu and Holiverse Yang
Building on our previous work on 2-Morita equivalence for $E_2$-
algebras using topological pictures, we develop a systematic framework for Morita equivalence of topological orders in different dimensions in terms of $n$-Morita categories $\mathrm{Mrt}_{E_n}(\mathcal{C})$. In this framework, various notions of $n$-Morita equivalence are unified as equivalences of objects in $\mathrm{Mrt}_{E_n}(\mathcal{C})$. We also compare the constructions of higher Morita categories due to Haugseng and to Gwilliam–Scheimbauer. For $n=1,2$, we prove that the functor $\mathrm{Mod}_n:\mathrm{Mrt}_{E_n}(\mathcal{C})\to \mathrm{Mrt}_{E_{n-1}}(\mathrm{LMod}^{\mathrm{rep}}(\mathcal{C}))$ is an equivalence, relating the algebraic description of higher Morita theory to its realization in terms of module categories. In this formulation, the notion of a bi-bimodule arises naturally and provides a common framework for local and confined modules. Its explicit orientation data, together with the corresponding fusion rules, clarifies the relations among defects arising from condensation in topological orders.
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Mesoscale and Nanoscale Physics
Occupation-Driven Josephson Diode in a Symmetric Junction
Jianxiong Zhai, Zelei Zhang and Jiawei Yan
We propose a Josephson diode mechanism in which nonreciprocity arises not from a conventional asymmetric Andreev spectrum but from nonequilibrium occupation of the current-carrying states engineered by attached reservoirs. We realize this mechanism in a double-
quantum-dot junction, where a phase-textured nonlocal reservoir acts as a
quantum Zeno selector: rapid dissipation freezes out the bright state directly coupled to the jump operator $L$, while preserving an orthogonal dark Andreev channel whose supercurrent remains comparable to that of the lossless junction. In the infinite-gap limit, the steady-state current factorizes as $I_{\rm ss}=I_A P_\gamma$, so that even when the Andreev current $I_A$ is strictly reciprocal, the phase asymmetry of $P_\gamma$ alone can produce a Josephson diode effect through reservoir engineering. We further show that local Coulomb repulsion can drive the system toward a nearly ideal diode regime via a dark-pair resonance. Using Keldysh-Lindblad calculations, we demonstrate that our results remain robust for realistic junctions with a finite superconducting gap and dissipation.
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Strongly Correlated Electrons
Multi-orbital physics in inverse Lieb lattice altermagnets
Mercè Roig, Jannik Gondolf, Andreas Kreisel et al. (+2 more)
The inverse Lieb
lattice has recently emerged as a promising platform for altermagnetism, with several materials with this structure proposed as $d$-wave altermagnetic candidates. Here, we develop a
symmetry-based microscopic
Hamiltonian for these materials that includes both sublattice and orbital degrees of freedom, going beyond the sublattice-only minimal models that have been extensively used to study such altermagnets. We apply these models to examine multi-orbital electron correlation physics in the vanadium oxychalcogenide family altermagnets, which contain dominant $xy$ and $xz/yz$ orbitals character at the Fermi level in the altermagnetic state. We demonstrate that $xy$ orbitals are crucial to stabilize the altermagnetic state observed within a single V$_2$O layer, and altermagnetic order in the $xz/yz$ orbitals is induced through Hund's coupling. Additionally, we show that these multi-orbital models reveal topological regimes in which topological edge states are naturally orbital selective.
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All authors Mercè Roig, Jannik Gondolf, Andreas Kreisel, Brian M. Andersen, Daniel F. Agterberg
Mesoscale and Nanoscale Physics
Terahertz anomalous Hall effect in magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$
Ashutosh Singh, Hongjing Xu, Xielin Wang et al. (+6 more)
Time-reversal-
symmetry-broken Weyl semimetals are known to have at least two nodes in their electronic band structure, separated in momentum space and acting as sources and sinks of Berry
curvature. This gives rise to a transverse Hall conductivity, known as the anomalous Hall effect (AHE), which, in the simplest two-node picture, is proportional to the momentum-space separation between the nodes in the zero frequency limit. In the recently discovered Weyl semimetal $\mathrm{Co_3Sn_2S_2}$, a giant AHE has been observed. However, experimental investigations in the low-energy regime, which directly probe quasiparticle excitations near the Weyl nodes, remain limited. Here, we present a systematic study of the intrinsic low-energy gyrotropic optical response of $\mathrm{Co_3Sn_2S_2}$ using terahertz spectroscopy combined with semianalytical calculations based on a physically intuitive effective model. Our results provide a robust and transparent explanation of the observed magnetooptical phenomena in terms of intrinsic gyrotropy arising from momentum-space separation of the Weyl nodes. Furthermore, quantitative comparison between experiment and theory places stringent constraints on the material parameters.
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All authors Ashutosh Singh, Hongjing Xu, Xielin Wang, Kohei Fujiwara, Atsushi Tsukazaki, Shengxi Huang, Andrey Baydin, Junichiro Kono, Alexey Belyanin
Materials Science · Cross-listed from physics.chem-ph
ElemCo.jl: A Julia package for electron-correlation methods
Daniel Kats, Charlotte Rickert, Thomas Schraivogel et al. (+3 more)
We present ElemCo.jl, an open-source Julia package for molecular electronic structure and properties calculations with a particular emphasis on Coupled Cluster and Distinguishable Cluster methods. The package provides a high-level, macro-based user interface which makes routine calculations accessible to users with no prior Julia experience. A newly developed visualizer, JLmol, assists in the graphical preparation of ElemCo.jl input files and displays results such as molecular orbitals. ElemCo.jl offers restricted closed-shell and unrestricted variants of state-of-the-art electron-correlation methods such as FCI, MP2, CCSD(T) as well as EOM-CCSD and the DC methods DCSD and DC-CCSDT. In addition to traditional approaches, ElemCo.jl provides recently developed methods that are currently unique to the package. These include tensor-decomposed implementations of DCSD and DC-CCSDT (SVD-DCSD and SVD-DC-CCSDT) as well as two-determinant and fixed-reference CC and DC methods. For excited-state calculations, ElemCo.jl also offers EOM-DCSD, which is benchmarked in this work against CC3 on the QUEST3
benchmark set, alongside EOM-CCSD. Furthermore, both ground and excited states, including those of multireference character, can be treated using CIPHI - an efficient selected Configuration Interaction (CI) approach employing a CIPSI/Heat-Bath-CI-based
algorithm. Users can directly invoke internal functions from the input file, enabling them to test and compose new methods without the need to modify ElemCo.jl's source code. Also, ElemCo.jl can be readily interfaced with external
quantum chemistry codes through the Fcidump format, for example as the high-level solver for transcorrelated
Hamiltonians, periodic embedded fragments, etc. We provide a detailed overview of ElemCo.jl's methodological repertoire and discuss its technical details and implementation, performance, interfaces, and usage.
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All authors Daniel Kats, Charlotte Rickert, Thomas Schraivogel, Kristoffer Simula, Denis Usvyat, Fangcheng Wu
Materials Science
Data-efficient crack quantification in lithium-ion cathodes using foundation model transfer
Thorsten Tegetmeyer-Kleine, Thomas Schmitt, Phillip Aquino et al. (+3 more)
Battery lifetime is central to sustainable electrification, yet the particle cracking that drives lithium-ion cathode aging is hard to measure: quantitative microscopy of this degradation is bottlenecked by annotation, because each destructive electron-microscopy cross-section spans hundreds of megapixels and pixel-level expert labelling requires hours per image. We show that a frozen self-supervised
vision-
transformer encoder, combined with a lightweight trainable decoder and iterative model-assisted annotation, turns this sparse labelling budget into population-scale degradation measurements. Applied to three 120-megapixel NMC cathode cross-sections representing initial, cycled-aged and calendar-aged states, the framework distinguishes intragranular cracks from early- and late-stage intergranular cracks and yields per-particle distributions of crack width, tortuosity and area fraction. Late intergranular crack coverage reaches 4.6% in the cycled sample versus 0.5% in the initial and calendar-aged samples, forming more tortuous, higher-coverage networks, consistent with degradation from repeated electrochemical cycling rather than elevated-temperature storage alone. A single destructive image yields the population-level statistics needed for lifetime-extending design, aging assessment and second-life decisions.
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All authors Thorsten Tegetmeyer-Kleine, Thomas Schmitt, Phillip Aquino, Christiane Rahe, Dirk Uwe Sauer, Weihan Li
Superconductivity · Cross-listed from physics.app-ph
Diamond quantum-sensing platform with integrated boron-doped diamond microwave antenna and thermometer
Masahiro Ohkuma, Ryo Matsumoto, Shintaro Adachi et al. (+5 more)
Wide-field nitrogen-vacancy (NV)
magnetic imaging at cryogenic temperatures requires microwave excitation and reliable knowledge of the temperature near the sensing region. Here, we report an integrated diamond
quantum-sensing platform combining an ensemble of NV centers with a boron-doped diamond (BDD) microwave
antenna and thermometer formed on the same diamond substrate. The BDD
antenna provides microwave excitation for optically detected
magnetic resonance measurements, and the BDD thermometer monitors the thermal environment near the NV sensing region. The BDD thermometer detected
laser-induced local heating that was not clearly resolved by a stage-mounted thermometer. Using this platform, we imaged the temperature-dependent Meissner response of multiple cuprate
superconductors while recording the temperature. These results demonstrate that the integrated BDD–NV platform provides a practical approach for cryogenic wide-field
magnetic imaging with integrated microwave delivery and local thermometry.
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All authors Masahiro Ohkuma, Ryo Matsumoto, Shintaro Adachi, Shinobu Onoda, Kensei Terashima, Takao Watanabe, Yoshihiko Takano, Keigo Arai