Statistical Mechanics
Finite-size corrections to the crosscap overlap in the two-dimensional Ising model
Yiteng Zhang, Li-Ping Yang, Hong-Hao Tu et al. (+1 more)
We analyze the finite-size corrections to the crosscap overlap in the two-dimensional classical Ising model along its self-dual critical line. Using a fermionic formulation, we express the
lattice crosscap overlap in terms of Bogoliubov angles and develop a contour-integral approach by analytically continuing the
lattice momentum to the complex plane. This leads to a remarkably simple expression for the crosscap overlap, which demonstrates that the finite-size corrections decay exponentially with system size. We further derive an exact analytical formula for the corresponding decay constant and show that it is determined by the complex singularity structure of the Bogoliubov angle.
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All authors Yiteng Zhang, Li-Ping Yang, Hong-Hao Tu, Yueshui Zhang
Soft Condensed Matter
Features distinguishing the flow behavior of polyelectrolytes with opposite charges in aqueous solutions
Suresha P. Ranganath, Manohar V. Badiger and Bernhard A. Wolf
Solution viscosities of a polycation and a polyanion in NaCl-water: HSAB-guided rheology The zero-shear viscosities of poly(3-acrylamido-propyl-trimethyl-ammonium-chloride) (PAPTMAC-Cl, M ~ 7.8 kDa) and poly(styrene-sulfonate sodium) (PSS-Na, M ~ 75.6 kDa) were measured in aqueous NaCl solutions at 25 degrees C over a wide range of salt concentrations. Extrapolation to zero
polymer concentration yields an intrinsic viscosity of 4 460 mL g^-1 for the polycation, i.e. roughly three times larger than that of the polyanion, although the polycation's molar mass is only one-tenth of the polyanion's. At low salinities the shear-overlap parameter S as a function of
polymer concentration c exhibits a pronounced maximum for PAPTMAC-Cl, whereas PSS-Na shows a clear inflection point. With increasing NaCl concentration both curves become linear, indicating that the system has entered a regime where the solute dominates the flow behavior. The crossover concentrations (S_crov) of the polycation are systematically larger than those of the polyanion. By applying Pearson's Hard-Soft Acid-Base (HSAB) concept we find that the observed differences are not a simple consequence of opposite
polymer charges. Rather they arise from the specific ion-pairing: the soft NR4+ group of PAPTMAC pairs with the hard Cl-, whereas the hard RSO3- units of PSS-Na interact with the hard Na+. This insight suggests that the rheological response of polyelectrolyte solutions can be deliberately tuned by choosing counter-ions of appropriate hardness/softness. Keywords: intrinsic viscosity, shear-overlap, polyelectrolytes, sodium chloride, HSAB theory, rheology, soft-matter.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Optically reconfigurable canalization of exciton-polaritons in a non-hyperbolic perovskite
Jiahao Ren, Olha Bahrova, Feng Jin et al. (+5 more)
The ability to steer polariton flow on-demand holds significant promise towards nanophotonic applications and photonic circuitry. Polariton canalization, exhibiting intrinsic collimation and diffractionless transport, emerges as a promising solution without guiding structures. However, earlier demonstrations have been restricted to certain
crystal surfaces with intrinsic
hyperbolic responses and operated in the linear regime. Here, we experimentally demonstrate canalization of nonlinear
exciton polariton condensates with optical reconfigurability in a birefringent CsPbBr3 perovskite
crystal without intrinsic
hyperbolic response. By
embedding the birefringent perovskite
crystal into a planar microcavity, the interplay between cavity transverse-electric-transverse-
magnetic splitting and crystalline birefringence produces an anisotropic band geometry with a
hyperbolic-flat-
parabolic evolution of polaritonic isofrequency contours (IFCs). Nonresonant pumping drives
exciton polariton condensation onto flat far-field contours with nonlinear emission amplification, leading to coherent canalized flows with over twentyfold collimation with respect to arc-shaped contours. Reconfiguring the optical pumping-spot size allows switching the nonlinear polariton condensates into
hyperbolic and
parabolic IFC regimes, leading to divergent propagation behaviour with collimating reconfiguration. Our study reveals a distinct canalization framework for shaping the nonlinear
exciton-polariton condensate flows, opening opportunities for all-optical polaritonic logic
circuits based on stabilized nonlinear
quantum interconnects.
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All authors Jiahao Ren, Olha Bahrova, Feng Jin, Hao Zheng, Dmitry Solnyshkov, Cheng-Wei Qiu, Guillaume Malpuech, Rui Su
Materials Science · Cross-listed from physics.optics
Hybrid Barium Titanate Waveguide Designs For Efficient Nonlinear Frequency Conversion
Trevor G. Vrckovnik, D. Arslan, F. Eilenberger et al. (+1 more)
Barium titanate (BaTiO$_3$) is emerging as a powerful integrated photonic material, combining strong $X^{(2)}$ and electro-optic nonlinearities with rapidly improving thin-film waveguide quality. Recent demonstrations of low-loss BaTiO$_3$ waveguides and high-Q resonators have established BaTiO$_3$-on-
insulator as a promising platform for next-generation frequency-conversion and
quantum photonic technologies. However, while BaTiO$_3$ electro-optic modulators are now well developed, nonlinear BaTiO$_3$ waveguide engineering remains comparatively immature. Techniques widely used in lithium niobate, such as periodic poling for quasi-phase-matching, are poorly suited to BaTiO$_3$ because epitaxial thin films exhibit high coercive fields, strong strain-clamping effects, multivariant domain structures, and slow, complex switching dynamics. These factors make accurate periodic poling challenging and hinder the development of efficient $X^{(2)}$ frequency converters. Here, we introduce a fabrication-robust alternative based on linear-nonlinear hybrid waveguides, where TiO$_2$ is selectively incorporated into BaTiO$_3$ ridge waveguides to enhance nonlinear mode overlap while relying solely on modal phase-matching. Using coupled-mode-theory simulations, we identify phase-matched geometries and show that the hybrid design achieves a 2.75x increase in normalized second harmonic generation efficiency over monolithic BaTiO$_3$ waveguides. The uniform, lithographically defined cross-section makes the approach highly scalable. These results position hybrid BaTiO$_3$-TiO$_2$ waveguides as a practical route to CMOS-compatible, high-efficiency $X^{(2)}$ devices for integrated
quantum photonics.
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All authors Trevor G. Vrckovnik, D. Arslan, F. Eilenberger, Sebastian W. Schmitt
Mesoscale and Nanoscale Physics · Cross-listed from math-ph
Vanishing of power-law corrections to Kubo's formula for the Hall current at incommensurate magnetic fields
Gabriele Mazzini and Domenico Monaco
We consider a non-interacting electron gas confined to a two-dimensional
crystal by the action of a perpendicular
magnetic field; in the one-particle approximation, the dynamics of the system is modelled by a spectrally gapped Bloch-Landau
Hamiltonian. No commensurability condition is assumed between the
magnetic flux per unit
cell and the
quantum of
magnetic flux. We construct a non-
equilibrium almost-stationary state (NEASS) which "dresses" the
equilibrium Fermi projection on states below the spectral gap, and models the state of the system after the addition of a weak external electric field of strength $\varepsilon \ll 1$. Having in mind applications to the integer
quantum Hall effect, we probe the response of a current operator in the direction transverse to that of the applied electric field, and show that the resulting current density in the NEASS is linear in $\varepsilon$, with no power-law corrections. The linear response coefficient, namely the
Hall conductivity, is computed in terms of the
equilibrium Fermi projection via the double-commutator formula, in accordance with the prediction from Kubo's linear response theory. Our results generalize the methods and findings of [Lett. Math. Phys. 112 (2022), 91] to the setting of uniform
magnetic fields with incommensurate
magnetic flux per unit
cell, and to
lattice-periodic perturbation of such
magnetic fields.
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Statistical Mechanics
High-precision Dynamic Monte Carlo Study of Rigidity Percolation
Mingzhong Lu, Yufeng Song, Qiyuan Shi et al. (+2 more)
Rigidity percolation provides an important basis for understanding the onset of mechanical stability in disordered materials. While most studies on the triangular
lattice have focused on static properties at fixed bond~(site) occupation probabilities, the dynamics of the
rigidity transition remain less explored. In this work, we formulate a dynamic pebble game
algorithm that monitors how rigid clusters emerge and evolve as bonds are added sequentially to an empty
lattice, with computational efficiency comparable to the standard static pebble game. We uncover a previously overlooked temporal self-similarity exhibited in multiple quantities, including the cluster size changes and merged cluster sizes during bond addition, as well as the number of simultaneously merging clusters. We identify large-scale cascade events in which a single bond addition triggers the merger of an extensive number of clusters that scales with system size with inverse correlation-length exponent. Using an event-based ensemble approach, we obtain high-precision estimates of the critical point $p_c = 0.660\,277\,8(10)$, the inverse correlation-length exponent $1/\nu = 0.850(3)$, and the fractal dimension $d_f = 1.850(2)$, representing substantial improvements over existing values.
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All authors Mingzhong Lu, Yufeng Song, Qiyuan Shi, Ming Li, Youjin Deng
Materials Science
Screening 39 billion protostructures for materials discovery
Abhijith S Parackal, Florian Trybel, Felix Andreas Faber et al. (+1 more)
Large-scale computational surveys are increasingly used to map the landscape of stable crystalline materials. We report a high-throughput energy screening of inorganic
crystals that enumerates binary and ternary compositions up to a specified unit-
cell complexity, yielding 39 billion protostructures. Candidates predicted to lie on or near the convex hull are retained, and their degrees of freedom are explored via Latin hypercube sampling followed by relaxation with machine-learned interatomic potentials. The resulting
dataset contains 81 million locally relaxed
crystal structures spanning 4495 ternary phase diagrams constructed from elements ranging from lithium to bromine and contains 88,498
crystal prototypes not present in existing
crystal-structure databases. The methods are validated both for three well-explored materials systems, Zr-Zn-N, Ti-Zn-N, and Hf-Zn-N, and by comparing with known data for structures resulting from the larger screening. The work provides a systematic map of low-energy compositional-structural space and a large, structured pool of candidates for downstream property evaluation and materials design.
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All authors Abhijith S Parackal, Florian Trybel, Felix Andreas Faber, Rickard Armiento
Materials Science
High-Pressure Torsion-Induced Transformation of Adenosine Monophosphate: Insights into Prebiotic Chemistry of RNA by Astronomical Impacts
Kaveh Edalati, Jacqueline Hidalgo-Jimenez and Thanh Tam Nguyen
The origin of life is yet a compelling scientific mystery that has sometimes been attributed to high-pressure impacts by small
solar system bodies such as comets, meteoroids, asteroids, and transitional objects. High-pressure torsion (HPT) is an innovative method with which to simulate the extreme conditions of astronomical impacts and offers insights relevant to prebiotic chemistry. In the present study, we investigated the polymerization and stability of adenosine monophosphate (AMP), a key precursor to ribonucleic acid (RNA), in dry and hydrated conditions (10 wt% water) under 6 GPa at ambient and boiling water temperatures. Comprehensive analyses with the use of X-ray diffraction, Raman spectroscopy,
Fourier-transform infrared spectroscopy,
nuclear magnetic resonance, scanning electron microscopy, and
matrix-assisted
laser desorption/ionization time-of-flight mass spectrometry revealed no evidence of polymerization, while AMP partly transformed to other organic compounds such as nucleobase-derived fragments of adenine, phosphoribose fragments, dehydrated adenosine, protonated adenosine, and oxidized adenosine. The torque measurements during HPT further highlight the mechanical behavior of AMP under extreme conditions. These findings suggest that, while HPT under the conditions tested does not facilitate polymerization, the formation of various compounds from AMP confirms the significance of astronomical impacts on the prebiotic chemistry of RNA on early Earth. Keywords: Ribonucleic acid (RNA), Origin of life; Phase transformations; Chemical reactions, Small
solar system bodies
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Mesoscale and Nanoscale Physics
Stimulated Magnonic Frequency Combs
Xueyu Guo, Tianci Gong, Guibin Lan et al. (+5 more)
Magnonic frequency combs, characterized by a series of discrete frequency lines, have emerged as a promising frontier in
magnon spintronics, with potential applications in advanced information processing and sensing technologies. Although the three-
magnon scattering process is widely recognized as a fundamental mechanism for generating these combs, its experimental realization has remained challenging due to the high threshold power and strict conservation of momentum and energy. In this work, we propose a novel mechanism for the stimulated generation of magnonic frequency combs that overcomes these limitations. Our approach offers precise and efficient control over key comb properties, including spacing between spectral lines and the number of lines, marking a significant advancement in the field. We substantiate this mechanism through a robust combination of theoretical modeling, micromagnetic simulations, and experimental validation. This study not only demonstrates the feasibility of our method but also opens new pathways for integrating magnonic frequency combs into practical spintronic devices.
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All authors Xueyu Guo, Tianci Gong, Guibin Lan, Mengying Guo, Xiufeng Han, Guoqiang Yu, Peng Yan, Qi Wang
Superconductivity
NMR/NQR and AC-susceptibility Studies in the Weyl Semimetal Superconductor 1T-MoTe$_2$ under Pressure
Takuto. Fujii, Hiroshi Yasuoka, Mukkattu Omanakuttan Ajeesh et al. (+5 more)
We performed the Te-
nuclear magnetic resonance, the Mo-
nuclear quadrupole resonance, and the AC susceptibility in the Weyl semimetal
superconductor 1T-MoTe$_2$ at pressures up to 2.17~GPa. From the temperature and pressure dependence of the AC susceptibility, the superconducting transition temperature $T_{\mathrm{c}}$ and the upper critical field $H_{\mathrm{c2}}$ were estimated. The results deviate from the Werthamer-Helfand-Hohenberg model but are well described by $H_{\mathrm{c2}}(T)=H_{\mathrm{c2}}(0)[1-T/T_{\mathrm{c}}]^{\alpha}$. The latter fit yields $H_{\mathrm{c2}}(0)=1.50$~T, $T_{\mathrm{c}}=3.81$K, and $\alpha=1.1$ at 2.17GPa, suggesting that the superconductivity lies in a strong-coupling regime. Since the
nuclear spin-
lattice relaxation rate divided by temperature, $1/T_1T$, follows the Korringa relation at ambient pressure, the increase in $1/T_1T$ with pressure up to approximately 0.7~GPa indicates an increase in the density of states (DOS), $N(E_\mathrm F)$. This trend mirrors the pressure dependence of $T_{\mathrm{c}}$ in the low-pressure region, consistent with the BCS mechanism. Above 0.7~GPa, however, $N(E_\mathrm F)$ slightly decreases while $T_{\mathrm{c}}$ continues to rise, suggesting an additional pairing contribution beyond the conventional BCS picture. In the 1T$^{\prime}$ phase at 2.17~GPa, the absence of a coherence peak in $1/T_1T$ around $T_{\mathrm c}$, accompanied by a two-step decrease just below $T_{\mathrm c}$, was observed, which may be a signature of unconventional superconductivity.
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All authors Takuto. Fujii, Hiroshi Yasuoka, Mukkattu Omanakuttan Ajeesh, Marcus. Schmidt, Takeshi Mito, Yu Liu, Cedomir Petrovic, Michael Baenitz
Materials Science
Numerical Diagonalization Study of the Phase Boundaries of the S=2 Heisenberg Antiferromagnet on the Orthogonal Dimer Lattice
Hiroki Nakano, Toru Sakai and Yuko Hosokoshi
The S=2 Heisenberg antiferromagnet on the orthogonal dimer
lattice is studied. The edges of the exact dimer and Neel-ordered phases in the ground state of the system are examined by the numerical diagonalization method. Our present results are discussed by combining them with previously obtained estimates for smaller-S cases. We find that an intermediate region between the exact dimer and Neel-ordered phases gradually widens as
spin S is increased up to S=2.
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Materials Science
Transferable mechanism of perpendicular magnetic anisotropy switching by hole doping in V$X_2$ ($X$=Te, Se, S) monolayers
John Lawrence Euste, Maha Hsouna and Nataša Stojić
The ability to tune and switch
magnetic anisotropy to a perpendicular orientation is a key challenge for implementing 2D magnets in spintronic devices. H-phase vanadium dichalcogenides V$X_2$ ($X$=Te, Se, S) are promising
ferromagnetic semiconductors with large
magnetic anisotropy energy (MAE). Recent work has shown that hole doping can switch their easy axis to out-of-plane, though the microscopic origin of this perpendicular
magnetic anisotropy (PMA) remains unclear. Using density-functional-theory calculations, we demonstrate that the PMA enhancement arises from first-order
spin-orbit coupling (SOC) acting on topmost degenerate valence states with nonzero orbital angular momentum projection ($m_l\ne 0$). In this case, the $\hat{L}_z\hat{S}_z$ term dominates for perpendicular magnetization, while in-plane orientations involve only weaker, second-order SOC contributions. The increased valence bandwidth leads to depletion of higher-energy states upon hole doping, stabilizing PMA. From this mechanism, we identify two transferable design principles for enhancing MAE under weak hole doping: (i) orbital degeneracy at the valence-band edge protected by point-group
symmetry and (ii) finite SOC in the degenerate
manifold. Notably, we identify multiple
magnetic semiconductors that meet these criteria and display enhanced MAE under hole doping. Furthermore, we show that band engineering can strategically place these degenerate orbitals at the valence band edge, significantly boosting PMA when hole-doped. We also examine trends in VTe$_2$, VSe$_2$, and VS$_2$ to determine the influence of
crystal-field splitting, exchange interaction, and orbital hybridization on the valence band edges. These results provide both a fundamental understanding of PMA switching upon hole doping and a transferable strategy for tuning
magnetic anisotropy, essential for designing high-performance spintronic materials.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Dispersive Microwave Sensing for Quantum Computing with Floating Electrons
Yiran Tian
In this dissertation, resonator-based readout techniques were developed for floating electrons as
qubits on cryogenic substrates, using two platforms: electrons on
liquid helium and electrons on solid neon. In addition, a cryogenic microwave source was developed to enable low-noise measurement for
qubit readout.
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Materials Science
Dynamically training machine-learning-based force fields for strongly anharmonic materials
Martin Callsen, Tai-Ting Lee and Mei-Yin Chou
Machine learning (ML) force fields have emerged as a powerful tool for computing materials properties at finite temperatures, particularly in regimes where traditional
phonon-based perturbation theories fail or cannot be extended beyond the harmonic approximation. These approaches offer accuracy comparable to ab initio molecular dynamics (MD), but at a fraction of the computational cost. However, their reliability critically depends on the quality and representativeness of the training data. In particular, static training
datasets often lead to failure when the force field encounters previously unseen atomic configurations during MD simulations. In this work, we present a framework for dynamically training ML force fields and demonstrate its effectiveness across materials with varying degrees of anharmonicity, including cubic boron arsenide (c-BAs), silicon (Si), and tin selenide (SnSe). Our method builds on the conventional
lattice dynamics expansion of total energy and incorporates
Bayesian error estimation to guide adaptive data acquisition during simulation. Specifically, we show that trajectory-averaged
Bayesian errors enable efficient and targeted exploration of the configuration space, significantly enhancing the robustness and transferability of the resulting force fields. We further demonstrate how
Bayesian error estimation can be applied to determine the convergence of the dynamic training without requiring additional ab initio data. This proposed framework offers a practical and easily implementable scheme to improve the training process, which is the most critical step in developing reliable ML force fields.
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Materials Science
Efficient high-harmonic generation in van der Waals ferroelectric NbOI$_2$ crystals
Tianchen Hu, Feng Li, Junhan Huang et al. (+8 more)
Layered NbOX$_2$ ($X=\mathrm{Cl,\,Br,\,I}$), a member of the van der Waals ferroelectric family, exhibits intrinsic ferroelectricity and pronounced nonlinear optical responses, making it a promising candidate for integrated nanophotonics applications. While previous studies have emphasized the material's strong second-order nonlinear responses, higher-order nonlinear responses are still mostly unexplored. This work systematically investigates NbOI$_2$ using high harmonic generation (HHG) spectroscopy. Driven by an intense mid-infrared
laser field centered at $\sim4~\mu\mathrm{m}$ wavelength, highly anisotropic odd- and even-order harmonics up to the 16th order are generated at a low peak intensity of $0.4~\mathrm{TW\,cm^{-2}}$, extending beyond the material's bandgap. Both bulk and flake forms of NbOI$_2$ display pronounced harmonic emission from the near-infrared to the deep-ultraviolet spectral region, with a notably high overall conversion efficiency compared to other known materials. Polarization-resolved measurements reveal that even-order harmonics remain aligned with the
crystal polar axis regardless of the driving-field orientation, whereas odd-order harmonics are dynamically affected. First-principles calculations suggest that the flat valence band associated with Peierls dimerization enhances HHG efficiency through electron correlation. These findings provide fresh perspectives on HHG in van der Waals ferroelectric materials and facilitate the development of compact and tunable
quantum light sources.
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All authors Tianchen Hu, Feng Li, Junhan Huang, Chen Qian, Ruoxuan Ding, Hao Wang, Qiaomei Liu, Qiong Wu, Ruifeng Lu, Chunmei Zhang, Nanlin Wang
Materials Science
Metal Halide Perovskites for Violet and Ultraviolet Light Emission
Sebastian Fernández, Manchen Hu, Tyler K. Colenbrander et al. (+2 more)
Emissive metal halide perovskites (MHPs) have emerged as excellent candidates for next-generation optoelectronics due to their sharp color purity, inexpensive processing, and bandgap tunability. However, the development of violet and ultraviolet light-emitting MHPs has lagged behind due to challenges related to material and device stability, charge carrier transport, tunability into the ultraviolet spectrum, toxicity, and scalability. Here, we review the progress of both violet and ultraviolet MHP nanomaterials and light-emitting diodes, including materials synthesis and device fabrication across various
crystal structures and dimensions (e.g., bulk thin films, 2D thin films, nanoplatelets, colloidal nanocrystals, and more) as well as lead-free platforms (e.g., rare-earth metal halide perovskites). By highlighting several pathways to continue the development of violet and ultraviolet light-emitting MHPs while also proposing tactics to overcome their outstanding challenges, we demonstrate the potential of state-of-the-art violet and ultraviolet MHP materials and devices for important applications in public health, 3D printing, nanofabrication, and more.
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All authors Sebastian Fernández, Manchen Hu, Tyler K. Colenbrander, Divine Mbachu, Daniel N. Congreve
Materials Science
Model-free Analysis of Scattering and Imaging Data with Escort-Weighted Shannon Entropy and Divergence Matrices
Jared Coles, Arthur R. C. McCray, Yue Li et al. (+9 more)
We demonstrate a model-free data analysis framework that leverages escort-weighted Shannon
Entropy and several divergence
matrices to detect phase transitions in scattering and imaging
datasets. By establishing a connection between physical
entropy and informational
entropy, this approach provides a sensitive method for identifying phase transitions without an explicit physical model or order parameter. We further show that pairwise divergence
matrices, including Kullback-Leibler divergence, Jeffrey Divergence, Jensen-Shannon Divergence and antisymmetric Kullback-Leibler divergence, provide more comprehensive measures of statistical changes than scalar
entropy alone. Our approach successfully detects the onset of both long- and short-range order in
neutron and X-ray scattering data, as well as a non-trivial phase transition in
magnetic skyrmion
lattices observed through Lorentz-transition electron microscopy. These results establish a framework for automated, model-free analysis of experimental data with broad applications in materials science and condensed matter physics.
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All authors Jared Coles, Arthur R. C. McCray, Yue Li, Bryan T. Fichera, Yan Wu, Yiqing Hao, Daniel Phelan, Yue Cao, Raymond Osborn, C. Phatak, Stephan Rosenkranz, Yu Li
Mesoscale and Nanoscale Physics
One-Dimensional Electronic States in a Moiré Superlattice of Twisted Bilayer WTe2
Takuto Kawakami, Hayato Tateish, Daiki Yoshida et al. (+10 more)
One-dimensional (1D) moiré superlattices provide a new route to engineering reduced-dimensional electronic states in van der Waals materials, yet their electronic structure and microscopic origin remain largely unexplored. Here, we investigate the structural relaxation and electronic properties of a 1D moiré superlattice formed in twisted
bilayer 1T$'$-WTe$_2$ using density functional theory calculations, complemented by high-angle annular dark-field scanning transmission electron microscopy. We show that
lattice relaxation strongly reconstructs the moiré stripes, leading to stacking-dependent stripe widths that are in excellent agreement with experimental observations. The relaxed structure hosts quasi-one-dimensional electronic bands near the
Fermi level, characterized by strong dispersion along the stripe direction and nearly flat dispersion in the perpendicular direction. By comparing the full
bilayer with isolated relaxed layers, we establish that these 1D electronic states are governed predominantly by an intralayer moiré potential induced by in-plane
lattice relaxation, rather than by interlayer hybridization. We extract this position-dependent moiré potential directly from DFT calculations and construct an effective tight-binding model that reproduces both the band dispersion and the real-space localization of the electronic wave functions. Our results identify
lattice relaxation as the key mechanism underlying 1D electronic states in 1D moiré superlattices. %and establish twisted
bilayer WTe$_2$ as a promising platform for exploring emergent one-dimensional moiré physics. The framework developed here provides a unified theoretical basis for realizing and exploring one-dimensional moiré physics in a broad class of anisotropic two-dimensional materials.
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All authors Takuto Kawakami, Hayato Tateish, Daiki Yoshida, Xiaohan Yang, Naoto Nakatsuji, Limi Chen, Kohei Aso, Yukiko Yamada-Takamura, Yoshifumi Oshima, Yijin Zhang, Tomoki Machida, Koichiro Kato, Mikito Koshino
Disordered Systems and Neural Networks · Cross-listed from cs.LG
Soft Quantization: Model Compression Via Weight Coupling
Daniel T. Bernstein, Luca Di Carlo and David Schwab
We show that introducing short-range attractive couplings between the weights of a neural network during training provides a novel avenue for model quantization. These couplings rapidly induce the discretization of a model's weight distribution, and they do so in a mixed-precision manner despite only relying on two additional hyperparameters. We demonstrate that, within an appropriate range of hyperparameters, our "soft quantization” scheme outperforms histogram-equalized post-training quantization on ResNet-20/CIFAR-10. Soft quantization provides both a new pipeline for the flexible compression of machine learning models and a new tool for investigating the trade-off between compression and generalization in high-dimensional loss landscapes.
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Soft Condensed Matter
Imperfect Turing Patterns: Diffusiophoretic Assembly of Hard Spheres via Reaction-Diffusion Instabilities
Siamak Mirfendereski and Ankur Gupta
Turing patterns are stationary, wave-like structures that emerge from the nonequilibrium assembly of reactive and diffusive components. While they are foundational in biophysics, their classical formulation relies on a single characteristic length scale that balances reaction and
diffusion, making them overly simplistic for describing biological patterns, which often exhibit multi-scale structures, grain-like textures, and inherent imperfections. Here, we integrate diffusiophoretically-assisted assembly of finite-sized
cells, driven by a background chemical gradient in a Turing pattern, while also incorporating intercellular interactions. This framework introduces key control parameters, such as the Péclet number,
cell size distribution, and intercellular interactions, enabling us to reproduce strikingly similar structural features observed in natural patterns. We report imperfections, including spatial variations in pattern thickness, packing limits, and pattern breakups. Our model not only deepens our understanding but also opens a new line of inquiry into imperfect Turing patterns that deviate from the classical formulation in significant ways.
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Materials Science
Bo Yuan, Yingxi Bai, Ying Dai et al. (+2 more)
Altermagnetism has attracted considerable interest, yet its associated spintronic phenomena have so far been largely confined to electronic systems. In this work, we uncover a universal
symmetry-based strategy for realizing topological altermagnets with the magnonic
quantum spin Hall effect, as evidenced by a nonzero
spin Chern number and protected helical edge states. Moreover, we demonstrate that
chiral magnon splitting in altermagnets gives rise to an intrinsically anisotropic, momentum-resolved thermal
Hall response, sharply contrasting with those in ferromagnets and antiferromagnets, thus offering enhanced flexibility for selective manipulation. As a concrete material realization, first-principles calculations and Heisenberg-DM model analysis reveal that V$_2$WS$_4$
bilayer exhibits $d$-wave altermagnetism, integer
spin Chern number with helical
magnon edge states, and the nonzero momentum-locked thermal
Hall conductivity. Our results establish a direct link between topological
magnons and altermagnetism, opening new avenues for dissipationless magnonic devices.
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All authors Bo Yuan, Yingxi Bai, Ying Dai, Baibiao Huang, Chengwang Niu
Mesoscale and Nanoscale Physics
Tunneling probe-based characterisation of the sp${}^3$ dangling bond on the H-C(100):$2\times1$ surface
Lachlan Oberg, Yi-Ying Sung, Cedric Weber et al. (+2 more)
The sp${}^3$ dangling bond on the diamond surface plays a critical role in the performance and fabrication of diamond
quantum technologies. For the former, the
magnetic and electric properties of this defect can impede the performance of
quantum sensors and computers. For the latter, the chemical properties of the dangling bond are integral to proposed methods for bottom-up fabrication of scalable diamond
quantum devices. In pursuit of high-performance, scalable diamond
quantum technology, tunnelling probe-based techniques offer the ability to create and modify the sp${}^3$ dangling bond with atomic-scale precision. However, these capabilities cannot be realised either deterministically or at scale without a means of identifying the sp${}^3$ dangling bond amidst the myriad of other defects on the diamond surface. Consequently, in this work we provide a comprehensive experimental and theoretical framework for STS-based characterisation of the sp${}^3$ defect on the H-terminated (100) diamond surface. This capability provides the foundation for future tunnelling probe studies in the modification of dangling bonds.
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All authors Lachlan Oberg, Yi-Ying Sung, Cedric Weber, Marcus W. Doherty, Christopher I. Pakes
Quantum Gases
Generating persistent-current superpositions in Bose-Einstein condensates using dynamic optical potentials
Renzo Testa and Donatella Cassettari
Precise and flexible manipulation of the motional state of ultracold atoms is a fundamental enabling technology for diverse applications such as
quantum sensing and
quantum computation. In this paper we propose a general, simple and highly efficient method to engineer the motional state of a Bose-Einstein condensate with time-dependent optical fields, which can be realized experimentally with existing light sculpting techniques. We demonstrate numerically how to engineer superpositions of persistent currents in a toroidal trap, achieving very high fidelity. We also study in detail the stability of the state over time, and we present an analytical two-state model that approximates well the
evolution of the state in presence of self-interactions.
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Materials Science · Cross-listed from hep-th
Electric birefringence in Euler-Heisenberg pseudo-electrodynamics
M. J. Neves
The
fermion sector of the pseudo-
quantum electrodynamics is integrated functionally to generate a non-linear electrodynamics, that it is called Euler-Heisenberg pseudo-electrodynamics. A non-local Chern-Simons topological term is added to the original lagrangian of the pseudo-
quantum electrodynamics in which a most complete electrodynamics gauge invariant in 1+2 dimensions is proposed. As consequence of the fermionic sector, we obtain a non-linear contribution in the electromagnetic fields that breaks the Lorentz
symmetry due to
Fermi velocity. From the Euler-Heisenberg pseudo-electrodynamics, we study the properties of the plane wave propagating in a planar medium under an uniform and constant electromagnetic background field. The properties of the planar material are discussed through the electric permittivity tensor and
magnetic permeability, that are functions of the frequency, wavelength and of the background fields. The dispersion relations and the refractive index are calculated in the presence of a uniform
magnetic field, and also in the case only of an electric background field. The birefringence phenomenon emerges only when the electric background field is considered.
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Statistical Mechanics
Continuum mechanics of entanglement in noisy interacting fermion chains
Tobias Swann and Adam Nahum
We develop an effective continuum description for information scrambling in a chain of randomly interacting Majorana
fermions. The approach is based on the semiclassical treatment of the path integral for an effective
spin chain that describes "two-replica" observables such as the
entanglement purity and the OTOC. This formalism gives exact results for the
entanglement membrane and for operator spreading in the limit of weak interactions. In this limit there is a large crossover lengthscale between free and interacting behavior, and this large lengthscale allows for a continuum limit and a controlled saddle-point calculation. The formalism is also somewhat different from that known from random
unitary circuits. The
entanglement membrane emerges as a kind of bound state of two travelling waves, and shows an interesting unbinding phenomenon as the velocity of the
entanglement membrane approaches the butterfly velocity.
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