Disordered Systems and Neural Networks · Cross-listed from cs.LG
Selective Imperfection as a Generative Framework for Analysis, Creativity and Discovery
Markus J. Buehler
We introduce materiomusic as a generative framework linking the hierarchical structures of matter with the compositional logic of music. Across
proteins, spider webs and flame dynamics, vibrational and architectural principles recur as tonal hierarchies, harmonic progressions, and long-range musical form. Using reversible mappings, from molecular spectra to musical tones and from three-dimensional networks to playable instruments, we show how sound functions as a scientific probe, an epistemic inversion where listening becomes a mode of seeing and musical composition becomes a blueprint for matter. These mappings excavate deep time: patterns originating in femtosecond molecular vibrations or billion-year evolutionary histories become audible. We posit that novelty in science and art emerges when constraints cannot be satisfied within existing degrees of freedom, forcing expansion of the space of viable configurations. Selective imperfection provides the mechanism restoring balance between coherence and adaptability. Quantitative support comes from exhaustive enumeration of all 2^12 musical scales, revealing that culturally significant systems cluster in a mid-
entropy, mid-defect corridor, directly paralleling the
Hall-Petch optimum where intermediate defect densities maximize material strength. Iterating these mappings creates productive collisions between human creativity and physics, generating new information as musical structures encounter evolutionary constraints. We show how swarm-based AI models compose music exhibiting human-like structural signatures such as small-world connectivity, modular integration, long-range coherence, suggesting a route beyond interpolation toward invention. We show that science and art are generative acts of world-building under constraint, with vibration as a shared grammar organizing structure across scales.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.class-ph
Electrostatics of a finite-thickness conducting cylindrical shell: coupled elliptic-kernel integral equations
J. Ricardo de Sousa
We develop an exact electrostatic formulation for a finite-length conducting cylindrical shell of finite thickness separating two dielectric media with arbitrary permittivity contrast. The boundary-value problem is reduced to a coupled system of singular integral equations with
elliptic kernels governing the induced surface-charge densities on the inner and outer faces. High-accuracy numerical solutions are combined with a systematic asymptotic analysis that elucidates the interplay between geometry, thickness, and dielectric contrast. All classical limiting regimes are recovered, including the slender-body limit, the short-cylinder (ring-like) asymptote, and the thick-shell regime dominated by the outer surface. We demonstrate that the logarithmic short-cylinder behavior of zero-thickness models is a singular feature, which is regularized for any finite thickness, giving rise instead to a finite capacitance plateau. The asymptotic structure of the coupled equations explains both the electrostatic decoupling of the inner cavity in the thick-shell limit and the redistribution of charge between the two surfaces. The results provide exact
benchmarks for finite cylindrical conductors, bridging classical analytical treatments and modern numerical approaches, and furnish a high-accuracy reference solution for the validation of axisymmetric electrostatic solvers.
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Materials Science · Cross-listed from physics.optics
Exploring Spectral Singularities and Topological Lasers in PT-Symmetric Weyl Semimetals
Arda Sevinc, Rama Alassadi and Mustafa Sarisaman
This paper investigates the unique properties of PT-symmetric Topological Weyl Semimetals (TWS) within the framework of non-Hermitian physics, focusing on their potential for generating topological
lasers. By exploring the role of spectral singularities and their relationship to exceptional points, we examine how these materials, characterized by Weyl nodes and topologically protected surface states, can support novel optical phenomena such as unidirectional propagation and enhanced lasing. Through a theoretical model based on the transfer
matrix approach, we reveal how the interplay between the PT
symmetry and the
axion term introduces new dynamics, leading to 12 distinct topological
laser configurations. The study also investigates the impact of the $\theta$-term on spectral singularities, showing how it quantizes the system's gain values and influences the topological properties of the
lasers. By applying our model to the TaAs material, a known Weyl semimetal, we uncover previously unreported effects, demonstrating the potential of PT-symmetric TWS materials for advanced optoelectronic applications. We show that the
axion-induced cyclotron-like
Hall current in a PT-symmetric TWS medium, revealing its topological characteristics and distinct flow patterns in the gain and loss regions, which serve as indicators of the system's topological
symmetry. Our findings open new avenues for the development of robust, tunable, and efficient topological
lasers with applications in
quantum information processing and beyond.
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Superconductivity
Superconducting Proximity Effect in an SSH-Superconductor Junction
I. A. Belkovich and A. A. Radkevich
A model of microscopic interaction between a
superconductor and a one-dimensional topological
insulator, an SSH chain, is considered. Using the functional integration method, the effective action of the interaction between a
superconductor and a topological
insulator is obtained. We obtain corrections to the quasiparticle excitation spectrum of the SSH chain due to tunneling in various limits and discuss the influence of phase fluctuations. We find that for bulk
superconductors, the states of the chain are stable for energies lying inside the superconducting gap while in lower-dimensional
superconductors phase fluctuations yield finite temperature-dependent lifetimes even inside the gap. We also discuss whether these results can be reproduced within a simple phenomenological approach.
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Mesoscale and Nanoscale Physics
Bridging Finite Element and Molecular Dynamics for Non-Fourier Thermal Transport Near Nanoscale Hot Spot
Tanvirul Abedien and Tianli Feng
Nanoscale hot spots forming tens of nanometers beneath the gate in advanced FinFET and HEMT devices drive heat transport into a non-
Fourier regime, challenging conventional (
Fourier-based) finite-element (FEM) analyses and complicating future thermal-aware chip design. Molecular dynamics (MD) naturally captures ballistic transport and
phonon nonequilibrium, but has not been applied to hot-spot problems due to computational cost. Here, we perform the first MD simulations of hot-spot heat transfer across ballistic-diffusive regimes and
benchmark them against FEM. We find that FEM using bulk thermal conductivity $\kappa_0$ significantly underestimates hot-spot temperature, even when the channel thickness is ~10 times the
phonon mean free path, indicating persistent non-
Fourier effects. We introduce a size-dependent "best" conductivity, $\kappa_{\mathrm{best}}$, using which FEM can reproduce MD hot-spot temperatures with high fidelity. We further decompose the MD-extracted thermal resistance into: (i) diffusive spreading, (ii) cross-plane ballistic, (iii) heat-carrier selective heating, and (iv) residual 3D ballistic-spreading resistances, and quantify each contribution. The resulting framework offers a practical route to embed non-
Fourier physics into FEM for hot-spot prediction, reliability assessment, and thermally aware design of next-generation transistors.
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Statistical Mechanics · Cross-listed from quant-ph
Spectroscopy of Quantum Phase Slips: Visualizing Complex Real-Time Instantons
Foster Thompson, Daniel K. J. Boneß, Mark Dykman et al. (+1 more)
Parametrically driven oscillators can emerge as a basis for the next generation of
qubits. Classically, these systems exhibit two stable oscillatory states with opposite phases. Upon quantization, these states turn into a pair of closely spaced Floquet states, which can serve as the logical basis for a
qubit. However, interaction with the environment induces phase-slip events which set a limit on
qubit coherence. Such phase slips persist even at zero temperature due to a mechanism known as
quantum activation \cite{QuantumActivation}. In contrast to conventional tunneling, the
quantum activation is described by a real-time instanton trajectory in the complexified phase space of the system. In this work, we show that the phase-slip rate is exponentially sensitive to weak AC perturbations. The spectrum of the system's response – captured by the so-called logarithmic susceptibility (LS) – enables a direct observation of characteristic features of real-time instantons. Studying this spectrum suggests new means of efficient
qubit control.
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All authors Foster Thompson, Daniel K. J. Boneß, Mark Dykman, Alex Kamenev
Materials Science
Connecting strain rate dependence of fcc metals to dislocation avalanche signatures
M. Aissaoui, C. Kahloun, O.U. Salman et al. (+1 more)
Strain rate sensitivity is a key feature of material deformation, whose importance is growing both because miniaturized components experience higher effective rates and because small scale simulations increasingly probe such conditions. As a dynamical characteristic, strain rate dependence is shown to be intimately connected to dislocation avalanches, which are a fundamental mechanism of dislocation dynamics. Using carefully designed, state of the art dislocation dynamics simulations in the intermediate range strain rate from 5 to 1000, we show that increasing strain rate promotes the activation of a growing number of stronger sites. The dislocation microstructure progressively rearranges into configurations with shorter segments. Dislocation avalanches become larger through the superposition of simultaneous events and because stronger obstacles are required to arrest them. As a result, the avalanche statistics are strongly affected by strain rate, with a reduced power law regime and an increasing power law exponent. Larger avalanches, in turn, lead to an enhanced dislocation storage rate. Contribution from collinear systems to avalanches and cross slip activity decreases, altering the fraction of screw dislocations and the resulting microstructure. These results provide an original mesoscopic picture of rate sensitivity in this strain rate range and offer a mechanistic interpretation of existing observations and findings from experiments and simulations.
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All authors M. Aissaoui, C. Kahloun, O.U. Salman, S. Queyreau
Statistical Mechanics · Cross-listed from physics.flu-dyn
Beyond chaos: fluctuations, anomalies and spontaneous stochasticity in fluid turbulence
Gregory L. Eyink and Nigel Goldenfeld
In this perspective, we consider the development of statistical hydrodynamics, focusing on the way in which the intrinsic stochasticity of turbulent phenomena was identified and is being explored. A major purpose of our discussion is to bring out the role of anomalies in turbulent phenomena, in ways that are not usually done, and to emphasize how the description of turbulent phenomena requires delicate considerations of asymptotic limits. The scope of our narrative includes selected historical aspects that are not usually emphasized, primarily due to G.I. Taylor, as well as discussions of certain aspects of the laminar-turbulent transition, the behaviour of turbulent drag at intermediate Reynolds numbers, and the statistics of fully-developed
turbulence that exhibit spontaneous stochasticity.
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Materials Science
Wafer-Scale Integration of Piezo- and Ferroelectric Al0.64Sc0.36N Thin Films by Reactive Sputtering
Sanjay Nayak, Venkata Raveendra Nallagatla, Ravindra Singh Bisht et al. (+19 more)
Large-area deposition of Aluminium-Scandium-Nitride (Al1-xScxN) thin films with higher Sc content (x) remains challenging due to issues such as abnormal orientation growth, stress control, and the undesired
crystal phase. These anomalies across the wafer hinder the development of high scandium-content AlScN films, which are critical for microelectromechanical systems applications. In this study, we report the sputter deposition of Al0.64Sc0.36N thin films from a 300 mm Al0.64Sc0.36
alloy target on 200 mm Si(100) wafers, achieving an exceptionally high deposition rate of 8.7 {\mu}m/h with less than 1% AOGs and controllable stress tuning. Comprehensive microstructural and electrical characterizations confirm the superior growth of high-quality Al0.64Sc0.36N films with exceptional wafer-average piezoelectric coefficients (d33,f =15.62 pm/V and e31,f = -2.9 C/m2) owing to low point defects density and grain mosaicity. This was accomplished through the implementation of an optimized seed layer and a refined electrode integration strategy, along with optimal process conditions. The wafer yield and device failure rates are analysed and correlated with the average stress of the films and their stress profiles along the diameter. The resulting films show excellent uniformity in structural, compositional, and piezoelectric properties across the entire 200 mm wafer, underscoring their strong potential for next-generation MEMS applications.
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All authors Sanjay Nayak, Venkata Raveendra Nallagatla, Ravindra Singh Bisht, Dmytro Solonenko, Demian Henzen, Washim Reza Ali, Carla Maria Lazzari, Robert JW Frost, Andrea Serafini, Davide Codegoni, Amalia Balsamo, Rossana Scaldaferri, Elaheh Allahyari, Anirban Ghosh, Martin Kratzer, Andrea Picco, Sonia Costantini, Andrea Rusconi, Mohssen Moridi, Humberto Campanella, Marco Deluca, Annalisa De Pastina
Statistical Mechanics · Cross-listed from math-ph
Quasicrystalline Gibbs states in 4-dimensional lattice-gas models with finite-range interactions
Jacek Miȩkisz and Siamak Taati
We construct a four-dimensional
lattice-gas model with finite-range interactions that has non-periodic, "quasicrystalline" Gibbs states at low temperatures. Such Gibbs states are probability measures which are small perturbations of non-periodic ground-state configurations corresponding to stacked tilings of the plane with Ammann's aperiodic tiles. Our construction is based on the correspondence between probabilistic cellular automata and Gibbs measures on their space-time trajectories, and a classical result on noise-resilient computing with cellular automata. The cellular automaton is constructed on the basis of Ammann's tiles, which are deterministic in one direction, and has non-periodic space-time trajectories corresponding to each valid tiling. Repetitions along two extra dimensions, together with an error-correction mechanism based on Toom's model, ensure stability of the trajectories in the presence of noise.
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Mesoscale and Nanoscale Physics
Inverted-Mode Scanning Tunneling Microscopy for Atomically Precise Fabrication
Eduardo Barrera, Bheeshmon Thanabalasingam, Rafik Addou et al. (+57 more)
Scanning Tunneling Microscopy (STM) enables fabrication of atomically precise structures with unique properties and growing technological potential. However, reproducible manipulation of covalently bonded atoms requires control over the atomic configuration of both sample and probe - a longstanding challenge in STM. Here, we introduce inverted-mode STM, an approach that enables mechanically controlled chemical reactions for atomically precise fabrication. Tailored molecules on a Si(100) surface image the probe apex, and the usual challenge of understanding the probe structure is effectively solved. The molecules can also react with the probe, with the two sides of the tunnel junction acting as reagents positioned with sub-angstrom precision. This allows abstraction or donation of atoms from or to the probe apex. We demonstrate this by using a novel alkynyl-terminated molecule to reproducibly abstract hydrogen atoms from the probe. The approach is expected to extend to other elements and moieties, opening a new avenue for scalable atomically precise fabrication.
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All authors Eduardo Barrera, Bheeshmon Thanabalasingam, Rafik Addou, Damian Allis, Aly Asani, Jeremy Barton, Tomass Bernots, Brandon Blue, Adam Bottomley, Doreen Cheng, Byoung Choi, Megan Cowie, Chris Deimert, Michael Drew, Mathieu Durand, Tyler Enright, Robert A. Freitas Jr., Alan Godfrey, Ryan Groome, Si Yue Guo, Sheldon Haird, Aru Hill, Taleana Huff, Christian Imperiale, Alex Inayeh, Jerry Jeyachandra, Mark Jobes, Matthew Kennedy, Robert J. Kirby, Mykhaylo Krykunov, Sam Lilak, Hadiya Ma, Adam Maahs, Cameron J. Mackie, Oliver MacLean, Michael Marshall, Terry McCallum, Ralph C. Merkle, Mathieu Morin, Jonathan Myall, Alexei Ofitserov, Sheena Ou, Ryan Plumadore, Adam Powell, Max Prokopenko, Henry Rodriguez, Sam Rohe, Luis Sandoval, Marc Savoie, Khalil Sayed-Akhmad, Ben Scheffel, Tait Takatani, D. Alexander Therien, Finley Van Barr, Dusan Vobornik, Janice Wong, Reid Wotton, Ryan Yamachika, Cristina Yu, Marco Taucer
Superconductivity
Insights Into Radiation Damage in YBa$_2$Cu$_3$O$_{7-\delta}$ From Machine-Learned Interatomic Potentials
Ashley Dickson, Niccolò Di Eugenio, Federico Ledda et al. (+10 more)
Accurate prediction of radiation damage in YBa$_2$Cu$3$O${7-\delta}$ (YBCO) is essential for assessing the performance of high-temperature superconducting (HTS) tapes in compact fusion reactors. Existing empirical interatomic potentials have been used to model radiation damage in stoichiometric YBCO, but fail to describe oxygen-deficient compositions, which are ubiquitous in industrial Rare-Earth Barium Copper
Oxide conductors and strongly influence superconducting properties. In this work, we demonstrate that modern machine-learned interatomic potentials enable predictive modelling of radiation damage in YBCO across a wide range of oxygen stoichiometries, with higher fidelity than previous empirical models. We employ two recently developed approaches: an Atomic Cluster Expansion (ACE) potential and a tabulated Gaussian Approximation Potential (tabGAP). Both models accurately reproduce Density Functional Theory (DFT) energies, forces, and threshold displacement energy distributions, providing a reliable description of atomic-scale collision processes. Molecular dynamics simulations of 5 keV cascades predict enhanced peak defect production and recombination relative to a widely used empirical potential, indicating different cascade
evolution. By explicitly varying oxygen deficiency, we show that total defect production depends only weakly on stoichiometry, offering insight into the robustness of radiation damage processes in oxygen-deficient YBCO. Finally, fusion-relevant 300 keV cascade simulations reveal amorphous regions with dimensions comparable to the superconducting coherence length, consistent with electron microscopy observations of
neutron-irradiated HTS tapes. These results establish machine-learned interatomic potentials as efficient and predictive tools for investigating radiation damage in YBCO across relevant compositions and irradiation conditions.
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All authors Ashley Dickson, Niccolò Di Eugenio, Federico Ledda, Daniele Torsello, Francesco Laviano, Flyura Djurabekova, Jesper Byggmästar, Mark R. Gilbert, Duc Nguyen-Manh, Erik Gallo, Antonio Trotta, Davide Gambino, Samuel T. Murphy
Strongly Correlated Electrons · Cross-listed from hep-th
Generalized Level-Rank Duality, Holomorphic Conformal Field Theory, and Non-Invertible Anyon Condensation
Clay Cordova, Diego García-Sepúlveda and Jeffrey A. Harvey
We study the interplay between holomorphic conformal field theory and dualities of 3D topological
quantum field theories generalizing the paradigm of level-rank duality. A holomorphic conformal field theory with a Kac-Moody subalgebra implies a topological interface between Chern-Simons gauge theories. Upon condensing a suitable set of anyons, such an interface yields a duality between topological field theories. We illustrate this idea using the $c=24$ holomorphic theories classified by Schellekens, which leads to a list of novel sporadic dualities. Some of these dualities necessarily involve condensation of anyons with non-abelian statistics, i.e. gauging non-invertible one-form global
symmetries. Several of the examples we discover generalize from $c=24$ to an infinite series. This includes the fact that
Spin$(n^{2})_{2}$ is dual to a twisted dihedral group gauge theory. Finally, if $-1$ is a quadratic residue modulo $k$, we deduce the existence of a sequence of holomorphic CFTs at central charge $c=2(k-1)$ with fusion category
symmetry given by $\mathrm{Spin}(k)_{2}$ or equivalently, the $\mathbb{Z}_{2}$-equivariantization of a Tambara-Yamagami fusion category.
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Quantum Gases · Cross-listed from quant-ph
Dissipation-Stabilized Quantum Revivals in a Non-Hermitian Lattice Gauge Theory
Yevgeny Bar Lev, Jad C. Halimeh and Achilleas Lazarides
With the advent of
quantum simulation experiments of
lattice gauge theories (LGTs), an open question is the effect of non-Hermiticity on their rich physics. The well-known PXP model, a U$(1)$ LGT with a two-level electric field in one spatial dimension, has become a paradigm of exotic physics in and out of
equilibrium. Here, we introduce a non-Hermitian version in which the
spin-flip rate differs between the two
spin directions. While the naive expectation is that non-Hermiticity might suppress coherent phenomena such as
quantum many-body scars, we find that when the facilitating direction of the
spin is disfavored, the oscillations are instead enhanced, decaying much slower than in the PXP limit. We demonstrate that this can be understood through a similarity transformation that maps our model to the standard PXP model, revealing that the oscillations are enhanced versions of the PXP scars. Our work provides an analytically tractable and conceptually simple example where non-Hermiticity enhances the stability of dynamically non-trivial coherent many-body modes.
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Soft Condensed Matter
Using Particle Shape to Control Defects in Colloidal Crystals on Spherical Interfaces
Gabrielle N. Jones, Philipp W.A. Schönhöfer and Sharon C. Glotzer
Spherical particles confined to a sphere surface cannot pack densely into a hexagonal
lattice without defects. In this study, we use hard particle Monte Carlo simulations to determine the effects of continuously deformable shape anisotropy and underlying
crystal lattice preference on inevitable defect structures and their distribution within colloidal assemblies of hard rounded polyhedra confined to a closed sphere surface. We demonstrate that cube particles form a simple square assembly, overcoming
lattice/
topology incompatibility, and maximize
entropy by distributing eight three-fold defects evenly on the sphere. By varying particle shape smoothly from cubes to spheres we reveal how the distribution of defects changes from square antiprismatic to icosahedral
symmetry. Congruent studies of rounded tetrahedra reveal additional varieties of characteristic defect patterns within three, four, and six-fold symmetric
lattices. This work has promising implications for programmable defect generation to facilitate different vesicle buckling modes using colloidal particle emulsions.
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Materials Science · Cross-listed from physics.optics
Achieving high-performance polarization-independent nonreciprocal thermal radiation with pattern-free heterostructures
Bach Do, Bardia Nabavi, Sina Jafari Ghalekohneh et al. (+3 more)
Many advanced energy harvesting technologies rely on advanced control of thermal emission. Recently, it has been shown that the emissivity and absorptivity of thermal emitters can be controlled independently in nonreciprocal emitters. While significant progress has been made in engineering these nonreciprocal thermal emitters, realizing a highly efficient, pattern-free emitter capable of supporting dual-polarization nonreciprocal emission remains a challenging task. Existing solutions are largely based on metamaterials and exhibit polarization-dependent behavior. This work proposes pattern-free multilayer
heterostructures combining magneto-optical and
magnetic Weyl semimetal materials and systematically evaluates their nonreciprocal emission performance for p- and s-polarized waves. The findings show that omnidirectional polarization-independent nonreciprocity can be achieved utilizing multilayer structures with different magnetization directions that do not follow simple vector summation. To further enhance the performance, Pareto optimization is employed to tune the key design parameters, enabling the maximization of nonreciprocal thermal emission in a given wavelength range. This approach offers a versatile strategy for designing high-performance thermal emitters tailored for multi-objective optical functionalities.
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All authors Bach Do, Bardia Nabavi, Sina Jafari Ghalekohneh, Taiwo Adebiyi, Bo Zhao, Ruda Zhang
Statistical Mechanics · Cross-listed from physics.med-ph
Analytical phase kurtosis of the constant gradient spin echo
Teddy X Cai, Nathan H Williamson and Peter J Basser
The Gaussian phase approximation (GPA) underlies many standard
diffusion magnetic resonance (MR) signal models, yet its validity is rarely scrutinized. Here, we assess the validity of the GPA by analytically deriving the excess phase kurtosis $\kappa_4/\kappa_2^2$, where $\kappa_n$ is the $n^{\text{th}}$ cumulant of the accumulated phase distribution due to motion. We consider the signal behavior of the
spin echo with constant gradient amplitude $g$ and echo time $T$ in several one-dimensional model systems: (1) a stationary Poisson pore-hopping model with uniform pore spacing $\Delta x$ and mean inter-hop time $\tau_{\text{hop}}$; (2) a trapped-release model in which
spin isochromats are initially immobilized and then released with diffusivity $D$ following an exponentially-distributed release time, $\tau_{\text{rel}}$; and (3) restricted
diffusion in a domain of length $L$. To our knowledge, this is among the first systematic analytical treatments of
spin echo phase kurtosis without assuming Gaussian compartments or infinitesimally short gradient pulses. In the pore-hopping system, $\kappa_4/\kappa^2_2 = (9/5)\tau_{\text{hop}}/T$, inversely proportional to the mean hop number, $T/\tau_{\text{hop}}$. In the trapped-release system, $\kappa_4/\kappa_2^2$ is positive and decreases roughly log-linearly with $T/\langle\tau_{\text{rel}}\rangle$, where $\langle\tau_{\text{rel}}\rangle$ is the average release time. For restriction, $\kappa_4/\kappa_2^2$ vanishes at small and large $L/\sqrt{DT}$, but has complicated intermediate behavior. There is a negative peak at $L/\sqrt{DT}\approx 1.2$ and a positive peak at $L/\sqrt{DT}\approx 4.4$. Monte Carlo simulations are included to validate the analytical findings. Overall, we find that the GPA does not generally hold for these systems under moderate experimental conditions, i.e., $T=10\;\mathrm{ms}$, $g\approx 0.2-0.6\;\mathrm{T/m}$.
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Mesoscale and Nanoscale Physics
Evidence of Spin-Valley Coupling in Dirac Material BaMnBi2 Probed by Quantum Hall Effect and Nonlinear Hall Effect
Subin Mali, Yingdong Guan, Lujin Min et al. (+2 more)
Valleytronics is a rapidly advancing field that explores the use of the valley degree of freedom in electronic systems to encode and process information. It relies on electronic states with
spin valley locking, first predicted and observed in monolayer transition metal dichalcogenides such as MoS2. However, very few bulk materials have been reported to host
spin valley locked electronic states. In this work, we present experimental evidence for a predicted, unique
spin valley locked electronic state generated by Bi zigzag chains in the layered compound BaMnBi2. We observe remarkable
quantum transport properties in this material, including a stacked
quantum Hall effect (QHE) and a nonlinear
Hall effect (NLHE). From the analysis of the QHE, we identify a
spin valley degeneracy of four, while the NLHE provides supporting evidence for the anticipated valley contrasted Berry
curvature, a typical signature of a
spin valley locked state. This
spin valley locked state contrasts with that observed in the sister compound BaMnSb2, where the degeneracy is two. This difference arises from significant variations in their orthorhombic
crystal structures and
spin orbit coupling. These findings establish a new platform for exploring coupled
spin valley physics in bulk materials and highlight its potential for valleytronic device applications.
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All authors Subin Mali, Yingdong Guan, Lujin Min, David Graf, Zhiqiang Mao
Strongly Correlated Electrons
Les Houches Lecture Notes on Tensor Networks
Bram Vancraeynest-De Cuiper, Weronika Wiesiolek and Frank Verstraete
Tensor networks provide a powerful new framework for classifying and simulating correlated and topological phases of
quantum matter. Their central premise is that strongly correlated matter can only be understood by studying the underlying
entanglement structure and its associated (generalised)
symmetries. In essence, tensor networks provide a compressed,
holographic description of the complicated
vacuum fluctuations in strongly correlated systems, and as such they break down the infamous many-body exponential wall. These lecture notes provide a concise overview of the most important conceptual, computational and mathematical aspects of this theory.
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Quantum Gases
Assembling a Bose-Hubbard superfluid from tweezer-controlled single atoms
William J. Eckner, Theodor Lukin Yelin, Alec Cao et al. (+4 more)
Quantum simulation relies on the preparation and control of low-
entropy many-body systems to reveal the behavior of classically intractable models. The development of new approaches for realizing such systems therefore represents a frontier in
quantum science. Here we experimentally demonstrate a new protocol for generating ultracold, itinerant many-body states in a tunnel-coupled two-dimensional optical
lattice. We do this by adiabatically connecting a near-ground-state-cooled array of up to 50 single strontium-86 atoms with a Bose-Hubbard superfluid. Through comparison with finite-temperature
quantum-Monte-Carlo calculations, we estimate that the
entropy per particle of the prepared many-body states is approximately $2 k_B$, and that the achieved temperatures are consistent with a significant superfluid fraction. This represents the first time that itinerant many-body systems have been prepared from rearranged atoms, opening the door to bottom-up assembly of a wide range of neutral-atom and molecular systems.
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All authors William J. Eckner, Theodor Lukin Yelin, Alec Cao, Aaron W. Young, Nelson Darkwah Oppong, Lode Pollet, Adam M. Kaufman
Materials Science
"X-ray Coulomb Counting" to understand electrochemical systems
Chuntian Cao and Hans-Georg Steinrück
Electrochemical systems are important for a sustainable and defossilized energy system of the future. While accurate and precise, the corresponding electrochemical measurements, in which many reactions may occur simultaneously, often do not contain enough information to understand the underlying mechanism and processes. This information, however, is crucial towards rational materials and devices as well as process development and for inventing innovative concepts. In this perspective, we introduce explicitly the concept of "X-ray Coulomb Counting" in which X-ray methods are used to quantify on an absolute scale how much charge is transferred into which reactions during the electrochemical measurements. This allows to interpret the electrochemical measurements in detail and obtain the desired phenomenological and mechanistic understanding. We show a few recent examples from the Li-ion battery literature in which the concept of X-ray Coulomb Counting was employed to obtain foundational understanding.
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Statistical Mechanics
Tethering effects on first-passage variables of lattice random walks in linear and quadratic focal point potentials
Debraj Das and Luca Giuggioli
Diffusion in a confining potential offers a minimal setting to understand the interplay between random motion and deterministic forces driving a particle towards a focal point or potential minimum. In continuous space and time, two extensively studied examples are Brownian motion in a linear (V-shaped) or a quadratic (U-shaped) potential. The deterministic bias towards the minimum is represented, respectively, by a constant force for the former and by an elastic restoring force that increases proportionally with distance for the latter. Surprisingly, unlike Brownian walks, random walks under focal point potentials in discrete space and time have received little
attention. Here, we bridge this gap by analysing the dynamics of
lattice random walkers in the presence of a V-shaped potential, both in a finite and an infinite spatial domain, and a finite U-shaped potential. For the V-potential in unbounded space, we find the generating function of the occupation probability and analyse the time dependence of the mean number of distinct sites visited, demonstrating that its long-time growth is logarithmic. We also study the first-passage probability and show that its mean may display a minimum as a function of bias strength, depending on the location of the initial and target sites relative to the focal point. Qualitatively similar dependencies in the first-passage probability and its mean appear for the finite U-potential. As a comparative analysis to the U-potential, we construct the bounded V-potential and superimpose in both cases a resetting process, in which the walker returns at random times to a site distinct from the focal point with some probability. We quantify the different effects of resetting on the steady-state probability and the first-passage dynamics in the two cases, and show a motion-limited regime emerges even for relatively moderate resetting probabilities.
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Materials Science · Cross-listed from physics.optics
From Disorder to Function: Entropy-Engineered Broadband Photonics with Ion-Transport-Stabilized Spectral Fidelity
Yuxiang Xin, Chen-Xin Yu, Jianru Wang et al. (+14 more)
The high-
entropy halide-perovskite field has expanded rapidly, yet a key gap remains: configurational
entropy is not yet a reliable, designable lever to co-deliver expanded photonic functionality and operational robustness with a composition-transferable mechanistic basis. Here we develop
entropy-engineered rare-earth halide double-perovskite single
crystals, Cs2Na(Sb, RE)Cl6 (RE3+ = Sc3+, Er3+, Yb3+, Tm3+), that simultaneously expand near-infrared (NIR) functionality and establish a mechanistic stability rule. Near-equiatomic B(III)-site alloying yields a single-phase high-
entropy solid solution (Delta_Sconfig about 1.6R). Sb3+ serves as a sensitizer that unifies excitation and cooperatively activates multiple lanthanide channels, transforming the parent single-mode response into a broadband NIR output (~850-1600 nm) with three spectrally orthogonal fingerprint bands at 996, 1220, and 1540 nm. This tri-peak, self-referenced output enables redundancy-based ratiometric solvent identification and quantitative mixture sensing with reduced susceptibility to intensity drift. Accelerated aging under humidity and oxygen shows improved phase and emission stability versus single-component analogues. DFT and molecular dynamics attribute the robustness to strongly suppressed RE$^{3+}$/Cl$^-$ self-
diffusion despite comparable H$_2$O/O$_2$ adsorption, kinetically impeding ion-migration-assisted reconstruction and degradation. Integration into a phosphor-converted LED delivers spectrally stable, broadband NIR illumination, establishing
entropy engineering as a practical handle to couple expanded photonic functionality with mechanistically accountable durability in metal-halide photonics.
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All authors Yuxiang Xin, Chen-Xin Yu, Jianru Wang, Jianbo Jin, Minliang Lai, Yinan Wang, Shuwen Yan, Gu-wen Chen, Liang Fan, Xiachu Xiao, Yutao Yang, Luying Li, Han Wang, Zhi-Pan Liu, Jiang Tang, Li-Ming Yang, Zhuolei Zhang
Superconductivity
Jian Xie, Zihao Huo, Zhimou Chen et al. (+5 more)
Recent studies of rhombohedral multilayer
graphene (RMG) have revealed a variety of superconducting states that can be induced or enhanced by
magnetic fields, reinforcing RMG as a powerful platform for investigating novel superconductivity. Here we report an
insulator-
superconductor transition driven by in-plane
magnetic fields B|| in rhombohedral hexalayer
graphene. The upper critical in-plane field of 2T violates the Pauli limit, and an analysis based on isospin
symmetry breaking supports a
spin-polarized
superconductor. At in-plane B = 0, such
spin-polarized
superconductor transitions into an
insulator, exhibiting a thermally activated gap of 0.1 meV. In addition, we observe four superconducting states in the hole-doped regime, as well as phases with orbital multiferroicity near charge neutrality point. These findings substantially enrich the phase diagram of rhombohedral
graphene and provide new insight into the microscopic mechanisms of superconductivity
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All authors Jian Xie, Zihao Huo, Zhimou Chen, Zaizhe Zhang, Kenji Watanabe, Takashi Taniguchi, Xi Lin, Xiaobo Lu
Soft Condensed Matter
Mixing, segregation, and collapse transitions of interacting copolymer rings
EJ Janse van Rensburg, E Orlandini, MC Tesi et al. (+1 more)
A system of two self and mutual interacting ring
polymers, close together in space, can display several competing
equilibrium phases and phase transitions. Using Monte Carlo simulations and combinatorial arguments on a corresponding
lattice model, we determine three
equilibrium phases, two in which the rings segregate in space and are either extended (the segregated-expanded phase) or compact (the segregated-collapsed phase). The third is a mixed phase where the rings interpenetrate. The corresponding phase boundaries are located numerically and their critical nature is discussed. Finally, by looking at the topological properties of the three phases, we show that the two rings are likely to be linked in the mixed phase and knotted in the segregated-collapsed phase.
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All authors EJ Janse van Rensburg, E Orlandini, MC Tesi, SG Whittington
Mesoscale and Nanoscale Physics
Geometry induced net spin polarization of $d$-wave altermagnets
Abhiram Soori
Altermagnets exhibit
spin-split electronic bandstructures despite having zero net magnetization, making them attractive for field-free spintronic applications. In this work, we show that a finite rectangular altermagnetic sample can acquire a net
spin polarization purely due to its geometry. This effect arises from the interplay between the anisotropic,
spin-resolved
Fermi contours of an altermagnet, the discrete sampling of momentum space and unequal sample dimensions. By explicitly counting occupied states, we demonstrate that rectangular samples with $L_x \neq L_y$ host a finite
spin polarization, which vanishes in the symmetric limit $L_x=L_y$ and in the thermodynamic limit. We further show that this geometry-induced
spin polarization can be directly probed in transport measurements. In the tunneling regime, the charge and the
spin conductances exhibit characteristic patterns as a function of sample dimensions, faithfully reflecting the underlying
spin polarization. In addition, transport across ferromagnet–altermagnet–ferromagnet junctions reveals an asymmetric magnetoresistance with respect to reversal of the Zeeman field, providing an independent transport signature of the finite
spin polarization. Our results establish geometry as an effective control parameter for
spin polarization in altermagnets and suggest a viable route for exploiting finite-size effects in mesoscopic altermagnetic spintronic devices.
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Mesoscale and Nanoscale Physics
Orbital magnetic octupole in crystalline solids and characterization of orbital altermagnetism
Takumi Sato and Satoru Hayami
Magnetic multipole moments beyond dipoles have emerged as key descriptors of unconventional electromagnetic responses in crystalline solids. However, a gauge-invariant bulk expression for orbital
magnetic multipole moments has remained elusive, hindering a unified understanding of their physical consequences. Here we formulate a gauge-invariant expression for the orbital
magnetic octupole moment in periodic
crystals and investigate its behavior in two models with distinct origins of magnetism: a spinless two-orbital model with orbital
magnetic order arising from complex hopping and a two-sublattice $d$-wave altermagnetic model based on
antiferromagnetic spin order. We also show that the orbital
magnetic octupole is naturally linked to a higher-rank
Hall response induced by spatially nonuniform electric fields, leading to a generalized Středa-type relation. Our results further demonstrate that the orbital
magnetic octupole provides a quantitative characterization of orbital altermagnetism.
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Materials Science
Tritium accumulation and ozone decontamination of tungsten and beryllium
Dominic Batzler, Robin Größle, Philipp Haag et al. (+5 more)
Tritium adsorption on surfaces creates a variety of issues, ranging from the fields of fusion applications to small and large-scale laboratory experiments using tritium. The extent to which tritium accumulates on surfaces is generally material-dependent and must be determined through experiments. Additionally, this surface contamination necessitates the implementation of appropriate decontamination procedures, preferably in-situ. A suitable method could be exposure to ozone during UV irradiation. However, it is currently not known if both components are necessary for the decontamination. At Tritium Laboratory Karlsruhe, both questions on contamination and decontamination can be addressed using a single experimental setup. With this, it is possible to expose solid samples to gaseous tritium to measure the temporal activity
evolution. Furthermore, the system can be filled with dry air, and dry air containing ozone to explore their decontamination effect. Both measurement modes were applied to beryllium and tungsten samples, which were chosen for their relevance in fusion. The beryllium surface was observed to accumulate tritium more than four times faster than tungsten when exposed to gaseous tritium. Concerning the decontamination, without simultaneous UV irradiation, exposure to ozone did not have any distinct effect on the surface activity compared to simply using dry air. This leads to the conclusion that UV illumination of the surfaces is required to achieve a significant decontamination factor.
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All authors Dominic Batzler, Robin Größle, Philipp Haag, Elizabeth Paine, Marco Röllig, Marie-Christine Schäfer, Marius Schaufelberger, Kerstin Trost
Superconductivity
Semiclassical theory for proximity-induced superconducting systems with spin-orbit coupling
Zhen-Cheng Liao, Cong Xiao, Zhi Wang et al. (+1 more)
We develop a semiclassical theory of superconducting quasiparticles for proximity-induced superconducting systems, where
spin-orbit coupling plays a critical role in shaping the quasiparticle dynamics. We reveal the structure of superconducting Berry
curvatures in such systems, and derived the superconducting Berry
curvature induced thermal Edelstein effect and
spin Nernst effect. We calculate these two thermo-
spin responses with model systems where Rashba
spin-orbit coupling, proximity induced superconductivity, and
ferromagnetic order are coexisting.
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All authors Zhen-Cheng Liao, Cong Xiao, Zhi Wang, Qian Niu
Quantum Gases
Sound waves in a backreaction-affected analogue spacetime: acoustic metric, mass, and correlations in Bose-Einstein condensates
Sang-Shin Baak and Hyun-Yong Lee
Analogue
gravity treats sound as a field on an effective spacetime set by the background flow, but
quantum fluctuations feed back on this background. Whether a condensate modified by such backreaction still defines a spacetime for the
quantum field remains open. Using a number-conserving expansion of a Bose-Einstein condensate, we show that in the sound-wave and eikonal approximations the first-order phase fluctuation propagates on an acoustic metric of the backreaction-corrected condensate and acquires a spacetime-dependent mass that cannot be absorbed into the metric. For a finite, quasi-one-dimensional gas after an interaction quench, backreaction enhances the equal-point phase correlation by about $10\%$ in the bulk and up to $20\%$ near the walls while the depletion remains below $2\%$; the bulk enhancement survives finite imaging resolution.
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