Peer Revenue Impact factor: volatile

Papers

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

Physics Condensed Matter

cond-mat Watch Condensed Matter

Tuesday 11 November

Soft Condensed Matter

Compliant Mechanisms for Invertible Poisson's Ratio and Tunable Stiffness in Cell Culture Substrates

Manu Sebastian, Sreenath Balakrishnan and Safvan Palathingal

The mechanical environment of a substrate plays a key role in influencing the behavior of adherent biological cells. Traditional tunable substrates have limitations as their mechanical properties cannot be dynamically altered in-situ during cell culture. We present an alternate approach by using compliant mechanisms that enable realization of tunable substrate properties, specifically, invertible Poisson's ratio and tunable stiffness. These mechanisms transition between positive and negative Poisson's effects with tunable magnitude through a bistable Engaging-Disengaging Compliant Mechanism (EDCM). EDCM allows stiffness between two points of the substrate to switch between zero and theoretically infinite. In the stiffened state, lateral deformation reverses under a constant axial load, while in the zero-stiffness state, the deformation direction remains outward as that of re-entrant structure. EDCM in conjunction with an offset mechanism also allows tuning of the effective stiffness of the entire mechanism. We present analytical models correlating geometric parameters to displacement ratios in both bistable states and through illustrative design cases, demonstrate their potential for designing dynamic and reconfigurable cell culture substrates.
Read the full abstract

Materials Science

Short-range order influences H distribution in Fe-Ni-Cr austenitic stainless steels

Tianyu Su, Brian J. Blankenau, Namhoon Kim et al. (+4 more)

Hydrogen embrittlement (HE) in austenitic stainless steels is advanced by hydrogen enhanced localized plasticity (HELP), typically accompanied by a transition from homogeneous to localized slip. Short-range order (SRO) in face-centered cubic (FCC) alloys is known to promote slip planarity, and recent studies suggest that H may amplify this localization behavior linked to inherent SRO. However, the manner in which the introduction of H affects SRO properties and, conversely, the manner that pre-existing SRO may affect H behavior, are not fully understood. In this work, a spin cluster expansion model combined with Monte Carlo simulation is employed to study the interplay between H and SRO in Fe-Ni-Cr alloys. Chemical order is quantified using Warren-Cowley SRO parameters, and the model predictions are validated against experimental data. We find that the presence of H only slightly alters the intrinsic ordering preference of the Fe-Ni-Cr alloys. As temperature decreases and the alloy evolves from disordered to ordered thermodynamic states, distinct H-metal correlations emerge. In particular, H-Ni and H-Cr pairs exhibit stronger ordering tendencies than H-Fe pairs, suggesting a selective affinity of H for certain atomic environments. On the other hand, we also find that compared to random alloys, when pre-existing SRO is present, it significantly affects the resulting H distribution by promoting local H enrichment in SRO domains. Such SRO-driven local H accumulation may facilitate slip localization and contribute to the early onset of embrittlement. These findings provide thermodynamic and structural insights into the interaction between H and SRO in austenitic stainless steels, highlighting possible implications on how the interaction between HELP and SRO brings about hydrogen embrittlement in austenitic stainless steels.
Read the full abstract

All authors Tianyu Su, Brian J. Blankenau, Namhoon Kim, Kshitij Vijayvargia, Petros Sofronis, Jessica A. Krogstad, Elif Ertekin

Materials Science · Cross-listed from eess.IV

Deep generative priors for robust and efficient electron ptychography

Arthur R. C. McCray, Stephanie M. Ribet, Georgios Varnavides et al. (+1 more)

Electron ptychography enables dose-efficient atomic-resolution imaging, but conventional reconstruction algorithms suffer from noise sensitivity, slow convergence, and extensive manual hyperparameter tuning for regularization, especially in three-dimensional multislice reconstructions. We introduce a deep generative prior (DGP) framework for electron ptychography that uses the implicit regularization of convolutional neural networks to address these challenges. Two DGPs parameterize the complex-valued sample and probe within an automatic-differentiation mixed-state multislice forward model. Compared to pixel-based reconstructions, DGPs offer four key advantages: (i) greater noise robustness and improved information limits at low dose; (ii) markedly faster convergence, especially at low spatial frequencies; (iii) improved depth regularization; and (iv) minimal user-specified regularization. The DGP framework promotes spatial coherence and suppresses high-frequency noise without extensive tuning, and a pre-training strategy stabilizes reconstructions. Our results establish DGP-enabled ptychography as a robust approach that reduces expertise barriers and computational cost, delivering robust, high-resolution imaging across diverse materials and biological systems.
Read the full abstract

All authors Arthur R. C. McCray, Stephanie M. Ribet, Georgios Varnavides, Colin Ophus

Mesoscale and Nanoscale Physics · Cross-listed from quant-ph

Emergent Decoherence Dynamics in Doubly Disordered Spin Networks

Cooper M. Selco, Christian Bengs, Chaitali Shah et al. (+2 more)

Elucidating the emergence of irreversible macroscopic laws from reversible quantum many-body dynamics is a question of broad importance across all quantum science. Many-body decoherence plays a key role in this transition, yet connecting microscopic dynamics to emergent macroscopic behavior remains challenging. Here, in a doubly disordered electron-nuclear spin network, we uncover an emergent decoherence law for nuclear polarization, $e^{-\sqrt{R_{p}t}}e^{-R_{d}t}$, that is robust across broad parameter regimes. We trace its microscopic origins to two interdependent decoherence channels: long-range interactions mediated by the electron network and spin transport within the nuclear network exhibiting anomalous, sub-diffusive dynamics. We demonstrate the capacity to control–and even eliminate–either channel individually through a combination of Floquet engineering and (optical) environment modulation. We find that disorder, typically viewed as detrimental, here proves protective, generating isolated electron-free clusters that localize polarization and prolong coherence lifetimes. These findings establish a microscopic framework for manipulating decoherence pathways and suggests engineered disorder as a new design principle for realizing long-lived quantum memories and sensors.
Read the full abstract

All authors Cooper M. Selco, Christian Bengs, Chaitali Shah, Zhuorui Zhang, Ashok Ajoy

Statistical Mechanics · Cross-listed from quant-ph

Local spreading of stabilizer Rényi entropy in a brickwork random Clifford circuit

Somnath Maity and Ryusuke Hamazaki

Nonstabilizerness, or magic, constitutes a fundamental resource for quantum computation and a crucial ingredient for quantum advantage. Recent progress has substantially advanced the characterization of magic in many-body quantum systems, with stabilizer Rényi entropy (SRE) emerging as a computable and experimentally accessible measure. In this work, we investigate the spreading of SRE in terms of single-qubit reduced density matrices, where an initial product state that contains magic in a local region evolves under brickwork random Clifford circuits. For the case with Haar-random local Clifford gates, we find that the spreading profile exhibits a diffusive structure within a ballistic light cone when viewed through a normalized version of single-qubit SRE, despite the absence of explicit conserved charges. We further examine the robustness of this non-ballistic behavior of the normalized single-qubit SRE spreading by extending the analysis to a restricted Clifford circuit, where we unveil a superdiffusive spreading. Finally, we discuss that a similar non-ballistic spreading within the light cone is found for another indicator of the magic, i.e., the robustness of magic.
Read the full abstract

Soft Condensed Matter

Fusion of two critical points and accelerated phase dynamics in orientational ternary mixtures

Hiroshi Yokota

Motivated by intracellular phase separation, we theoretically investigate how molecular orientation and multi-component nature affect phase behavior. We construct a minimal model for a ternary mixture composed of isotropic (I), anisotropic (A), and solvent (s) components by combining the Flory-Huggins and Maier-Saupe theories. We obtain two main results from evaluating the phase behavior and the time evolution of the density fields. First, for certain interaction parameters, two distinct binodal lines appear in the plane of the volume fractions of the I- and A-components, and merge through their respective critical points. Second, rapid droplet formation emerges due to a weakly first-order phase transition, characterized by a discontinuity of the spinodal surface. The first result indicates the possibility of continuous transformation between the two phase-separated states. The second result suggests that anisotropic molecules can regulate phase separation kinetics. These findings might be physically general beyond biological systems.
Read the full abstract

Soft Condensed Matter · Cross-listed from physics.flu-dyn

Wave-crests around obstacles in odd viscous liquids

E. Kirkinis and A. Levchenko

The values of liquid odd-viscosity coefficients remain largely unknown, with only a single experimental measurement reported to date [Nature Physics 15, 1188 (2019)]. In this work, inspired by the well-known consequences of dispersion surfaces in classical liquids from the work of Lighthill, we theoretically determine the shapes of constant-phase wave crests formed around obstacles moving at constant velocity in two- and three-dimensional odd viscous liquids, which may or may not undergo rigid rotation. From this analysis, we derive parametric relations that the odd-viscosity coefficients must satisfy, providing a framework for their experimental determination.
Read the full abstract

Strongly Correlated Electrons

Pseudogap and strange metal states in the square-lattice Hubbard model: A comprehensive study

Arata Tanaka

To clarify the origin of the pseudogap and strange metal states as well as their mutual relationship in cuprate superconductors, a comprehensive study on the spectral function, Fermi surface, resistivity and dynamical spin susceptivity of the Hubbard model on the square lattice has been conducted by means of the ladder dual-fermion approximation with an electron self-energy correction. It is found that the appearance of these two states requires that the characteristic hole concentration below which the Mott-Heisenberg and Slater mechanisms of electron localization occurs $p_{\rm MS}$ nearly coincides with the hole concentration where the Van Hove singularity (VHS) point is placed at the vicinity of the Fermi level. When this condition is met the VHS point is pinned at which the nesting condition of the antiferromagnetic (AFM) fluctuation is fulfilled almost everywhere on the Fermi surface in wide range of the hole concentration in a metallic state, i.e., the strange metal state. The spin fluctuation of the strange metal state is nearly quantum critical and the dynamical spin susceptivity is well described by overdamped spin wave having the $\omega/T$ scaling with the relaxation rate at the Planckian limit. Because of these distinctive features of the strange metal state, the $k$ dependence of scattering rate of electrons is small and electrons behave as the marginal Fermi liquid, resulting in $T$-linear resistivity. In contrast, the pseudogap state is magnetically in the renormalized classical regime and the pseudogap is formed near the X point where the nesting condition of the short-range AFM order is fulfilled.
Read the full abstract

Materials Science

Control of Spontaneous Orientation Polarization in Organic Semiconductors: The Role of Molecular Structure and Film Growth Conditions

Albin Cakaj, Markus Schmid, Alexander Hofmann et al. (+1 more)

Spontaneous orientation polarization (SOP) occurs when molecules with a finite permanent dipole moment are grown as thin films by physical vapor deposition and their alignment is such that a net non-zero polarization remains. We discuss how SOP in organic semiconductors can be controlled by the design of molecules as well as the film growth conditions and discuss its relevance in organic light-emitting devices.
Read the full abstract

All authors Albin Cakaj, Markus Schmid, Alexander Hofmann, Wolfgang Brütting

Monday 10 November

Strongly Correlated Electrons

High-order coupling as a driver for Mott insulating behavior in Holography

Lin-Yue Bai, René Meyer and Zhen-Hua Zhou

We construct a simple holographic model incorporating higher-order coupling terms for electron self-interactions. It can exhibit typical behavior of a Mott insulator, including a metal-insulator transition and a decrease in DC conductivity with the increase of charge density. In the analysis of AC conductivity, a soft gap is generally observed. Notably, when the DC conductivity approaches zero, the AC conductivity reveals a multi-peak structure, which can be attributed to the Mott and charge-transfer gaps observed experimentally in transition metals. With the increase of DC conductivity, the multi-peak structure gradually reverts to soft-gap behavior or even metallic conductivity. The accuracy of the numerical result is guaranteed by $\sigma(\omega\to 0)=\sigma_{DC}$ and sum rules.
Read the full abstract

Materials Science · Cross-listed from cs.CL

Large language models in materials science and the need for open-source approaches

Fengxu Yang, Weitong Chen and Jack D. Evans

Large language models (LLMs) are rapidly transforming materials science. This review examines recent LLM applications across the materials discovery pipeline, focusing on three key areas: mining scientific literature , predictive modelling, and multi-agent experimental systems. We highlight how LLMs extract valuable information such as synthesis conditions from text, learn structure-property relationships, and can coordinate agentic systems integrating computational tools and laboratory automation. While progress has been largely dependent on closed-source commercial models, our benchmark results demonstrate that open-source alternatives can match performance while offering greater transparency, reproducibility, cost-effectiveness, and data privacy. As open-source models continue to improve, we advocate their broader adoption to build accessible, flexible, and community-driven AI platforms for scientific discovery.
Read the full abstract

Mesoscale and Nanoscale Physics

Dephasing-induced Quantum Hall Criticality in the Quantum Anomalous Hall system

Fei Yang and Dong E. Liu

Conventional wisdom holds that static disorder is indispensable to the integer quantum Hall effect, underpinning both quantized plateaus and the plateau-plateau transition. We show that pure dephasing, without elastic disorder, is sufficient to generate the same $\theta$ driven criticality. Starting from a Keldysh formulation, we derive an open system nonlinear $\sigma$ model (NL$\sigma$M) for class A with a topological $\theta$ term but no Cooperon sector, and we demonstrate that nonperturbative instantons still govern a two parameter flow of $(\sigma_{xx},\sigma_{xy})$. Evaluating $\theta$ in a dephasing quantum anomalous Hall setting, we predict a quantum Hall critical point at $\sigma_{xy}=1/2$ with finite $\sigma_{xx}$ the hallmark of the integer quantum Hall universality class realized without Anderson localization. Boundary driven simulations of the Qi_Wu_Zhang model with local dephasing confirm this prediction and provide an experimentally aligned protocol to extract $(\sigma_{xx},\sigma_{xy})$ from Hall potential maps. By establishing dephasing as a self contained route to Hall criticality, our framework reframes plateau physics in open solid state and cold atom platforms and offers practical diagnostics for topological transport in nonunitary matter.
Read the full abstract

Statistical Mechanics

Random initial data and average shock time in the Fermi-Pasta-Ulam-Tsingou chain

Matteo Gallone, Ricardo Grande, Antonio Ponno et al. (+2 more)

We investigate the dynamics of the Fermi–Pasta–Ulam–Tsingou chain with long-wavelength random initial data. When the energy per particle is small, thermal equilibrium is not reached on a fast timescale and the system enters prethermalization. The formation of the prethermal state is characterized by the development of a Burgers-type shock and the onset of a turbulent-like spectrum with a time dependent exponent $\zeta(t)$ in the inertial range. We perform a significant step forward by demonstrating that these features are robust under generic long-wavelength random initial conditions. By employing advanced probabilistic techniques inspired by the works of Dudley and Talagrand, we derive a sharp asymptotic expression for the average shock time in the thermodynamic limit. For large $p$, this time scales as $(p \sqrt{\log p})^{-1}$, where $p$ is the number of excited modes proving that it is an intensive quantity up to a logarithmic correction in the size of the system.
Read the full abstract

All authors Matteo Gallone, Ricardo Grande, Antonio Ponno, Stefano Ruffo, Erwan Druais

Strongly Correlated Electrons

Topological Metal-Insulator Transition within the Ferromagnetic state

Ola Kenji Forslund, Chin Shen Ong, Moritz M. Hirschmann et al. (+20 more)

A major challenge in condensed matter physics is integrating topological phenomena with correlated electron physics to leverage both types of states for next-generation quantum devices. Metal-insulator transitions (MITs) are central to bridging these two domains while simultaneously serving as 'on-off' switches for electronic states. Here, we demonstrate how the prototypical material of K2Cr8O16 undergoes a ferromagnetic MIT accompanied by a change in band topology. Through inelastic x-ray and neutron scattering experiments combined with first-principles theoretical calculations, we demonstrate that this transition is not driven by a Peierls mechanism, given the lack of phonon softening. Instead, we establish the transition as a topological MIT within the ferromagnetic phase (topological-FM-MIT) with potential axionic properties, where electron correlations play a key role in stabilizing the insulating state. This work pioneers the discovery of a topological-FM-MIT and represents a fundamentally new class of topological phase transitions, revealing a unique pathway through which magnetism, topology, and electronic correlations interact.
Read the full abstract

All authors Ola Kenji Forslund, Chin Shen Ong, Moritz M. Hirschmann, Nicolas Gauthier, Hiroshi Uchiyama, Christian Tzschaschel, Daniel G. Mazzone, Romain Sibille, Antonio M. dos Santos, Masafumi Horio, Elisabetta Nocerino, Nami Matsubara, Deepak John Mukkattukavil, Konstantinos Papadopoulos, Kazuya Kamazawa, Kazuhiko Ikeuchi, Hidenori Takagi, Masahiko Isobe, Jun Sugiyama, Johan Chang, Yasmine Sassa, Olle Eriksson, Martin Månsson

Materials Science

Nanorod Pair Complexes Manipulated via Magnetic Casimir Forces

S Pal, L. M. Woods, C. Persson et al. (+3 more)

Controlling nanoscale interactions to suppress aggregation from short-range attractive forces is a key problem in nanoengineering. Here, we demonstrate a route to modulate Casmir-Lifshitz interactions between anisotropic nanoparticles with the magnetic fluids. By semi-classical quantum electrodynamics, we study ground state dispersion forces for cylindrical dielectric nanorods made of polystyrene (PS), and zinc oxide (ZnO) embedded in toluene-based host media with gold-coated magnetite nanoparticles and also predict magnetic contributions to the non-retarded excited state interaction. The variation in magnetic permeability enables tuning between repulsive and attractive interaction and a thermally unstable and measurable magnetic Casimir traps are predicted between a pair of ZnO-PS nanoparticles whose equilibrium position can be modulated over an order of magnitude with a small variation in the size of the magnetite nanoparticle. This provides an alternative magnetic Casimir-effect pathway to reversibly tune quantum electromagnetic forces at the nanoscale for assembly and enhancement of colloidal stability.
Read the full abstract

All authors S Pal, L. M. Woods, C. Persson, I. Brevik, U. De Giovannini, M. Boström

Strongly Correlated Electrons

Hidden symmetry-breaking in a kagome Ising ferromagnet

Tianxiong Han, Tyler J. Slade, Liqin Ke et al. (+15 more)

Kagome metals can host unconventional electronic phenomena that emerge from their frustrated lattice geometry and associated band topology. Correlated electronic orders, such as charge-density waves and superconductivity, are observed to intertwine with subtle time-reversal symmetry breaking whose microscopic origin is not currently understood. Here, we provide evidence for such time-reversal symmetry breaking in the kagome metal TbV$_6$Sn$_6$ arising from staggered magnetic moments within the kagome layers. TbV$_6$Sn$_6$ consists of metallic V kagome layers separated by Tb triangular layers that host Ising ferromagnetic order. Deep in the ferromagnetic state, the Tb Ising doublet ground state should display a single, dispersionless spin-flip excitation. Instead, inelastic neutron scattering reveals two sharp excitations associated with inequivalent Tb sites, demonstrating that a symmetry-broken phase coexists with Ising ferromagnetism. No additional structural or magnetic phase transitions are detected, and first-principles calculations rule out lattice distortions as the origin of the splitting. We attribute this effect to time-reversal symmetry breaking encoded by small V moments that couple to the Tb sublattice and leave a measurable spectral fingerprint. Our results establish rare-earth local moment spectroscopy as a sensitive probe of subtle broken symmetries and highlight an unexpected interplay between kagome magnetism and rare-earth local moment magnetism.
Read the full abstract

All authors Tianxiong Han, Tyler J. Slade, Liqin Ke, Qing-Ping Ding, Minseong Lee, Ryan D. McKenzie, Bing Li, Durba R. Jaishi, Yongbin Lee, Daniel M. Pajerowski, Qiang Zhang, Tao Hong, Paul C. Canfield, Yuji Furukawa, Komalavalli Thirunavukkuarasu, Aashish Sapkota, Rebecca Flint, Robert J. McQueeney

Strongly Correlated Electrons

Magnetic structure evolution and magnetoelastic coupling across the spin reorientation transition in TmCrO3

Vishesh Sharma, Gaurav Gautam, Poonam Yadav et al. (+5 more)

We present a comprehensive study of the magnetic structure evolution across the spin reorientation transition in orthorhombic (Pnma) TmCrO3. Magnetic susceptibility reveals canted antiferromagnetic (CAFM) ordering at T_N = 125 K, two compensation points (T_comp1 and T_comp2), followed by magnetization reversal with a magnetic susceptibility minimum between T_comp1 and T_comp2. Heat capacity shows a sharp lambda-type transition at T_N, associated with the long-range antiferromagnetic ordering of Cr, followed by a broad feature near 9 K. Neutron powder diffraction (NPD) establishes the Pn'm'a (Gamma2) magnetic structure below T_N. A gradual change in magnetic structure occurs during the spin-reorientation (SRO) transition below 30 K, where the magnetic symmetry transforms from Pn'm'a (Gamma2) to Pn'ma' (Gamma4) phase. However, below the SRO, neither Gamma2 nor Gamma4 alone adequately fit the intensity of magnetic reflections. A satisfactory refinement is achieved using the monoclinic subgroup P21'/c', derived from a combination of Gamma2 and Gamma4. The gradual SRO of Tm and Cr moments across the compensation regime is consistent with the magnetic symmetry P21'/c'. Furthermore, the ordered moments of Cr and Tm in TmCrO3 exhibit a complex, non-monotonic temperature dependence, with the Tm sublattice driving the spin-reorientation transition near the compensation point. Anomalies in the lattice parameters reveal strong magnetoelastic coupling, linking structural distortions to the SRO.
Read the full abstract

All authors Vishesh Sharma, Gaurav Gautam, Poonam Yadav, Chin-Wei Wang, Kaya Wei, N. P. Lalla, Theo Siegrist, Shivani Sharma

Superconductivity

Superconductivity in the two-dimensional Hubbard model revealed by neural quantum states

Christopher Roth, Ao Chen, Anirvan Sengupta et al. (+1 more)

Whether the ground state of the square lattice Hubbard model exhibits superconductivity remains a major open question, central to understanding high temperature cuprate superconductors and ultra-cold fermions in optical lattices. Numerical studies have found evidence for stripe-ordered states and superconductivity at strong coupling but the phase diagram remains controversial. Here, we show that one can resolve the subtle energetics of metallic, superconducting, and stripe phases using a new class of neural quantum state (NQS) wavefunctions that extend hidden fermion determinant states to Pfaffians. We simulate several hundred electrons using fast Pfaffian algorithms allowing us to measure off-diagonal long range order. At strong coupling and low hole-doping, we find that a non-superconducting filled stripe phase prevails, while superconductivity coexisting with partially-filled stripes is stabilized by a negative next neighbor hopping t-prime, with |t-prime| > 0.1. At larger doping levels, we introduce momentum-space correlation functions to mitigate finite size effects that arise from weakly-bound pairs. These provide evidence for uniform d-wave superconductivity at U = 4, even when t-prime = 0. Our results highlight the potential of NQS approaches, and provide a fresh perspective on superconductivity in the square lattice Hubbard model.
Read the full abstract

All authors Christopher Roth, Ao Chen, Anirvan Sengupta, Antoine Georges

Mesoscale and Nanoscale Physics

High-speed antiferromagnetic domain walls driven by coherent spin waves

Kyle L. Seyler, Hantao Zhang, Daniel Van Beveren et al. (+4 more)

The ability to rapidly manipulate domain walls (DWs) in magnetic materials is key to developing novel high-speed spintronic memory and computing devices. Antiferromagnetic (AFM) materials present a particularly promising platform due to their robustness against stray fields and their potential for exceptional DW velocities. Among various proposed driving mechanisms, coherent spin waves could potentially propel AFM DWs to the magnon group velocity while minimizing dissipation from Joule heating. However, experimental realization has remained elusive due to the dual challenges of generating coherent AFM spin waves near isolated mobile AFM DWs and simultaneously measuring high-speed DW dynamics. Here we experimentally realize an approach where ultrafast laser pulses generate coherent spin waves that drive AFM DWs and develop a technique to directly map the spatiotemporal DW dynamics. Using the room-temperature AFM insulator Sr$_2$Cu$_3$O$_4$Cl$_2$, we observe AFM DW motion with record-high velocities up to ~50 km/s. Remarkably, the direction of DW propagation is controllable through both the pump laser helicity and the sign of the DW winding number. This bidirectional control can be theoretically explained, and numerically reproduced, by the DW dynamics induced by coherent spin waves of the in-plane magnon mode - a phenomenon unique to magnets with an easy-plane anisotropy. Our work uncovers a novel DW propulsion mechanism that is generalizable to a wide range of AFM materials, unlocking new opportunities for ultrafast coherent AFM spintronics.
Read the full abstract

All authors Kyle L. Seyler, Hantao Zhang, Daniel Van Beveren, Costel R. Rotundu, Young S. Lee, Ran Cheng, David Hsieh

Strongly Correlated Electrons

Non-Reciprocal Zone Boundary Magnon Propagation in Cu$_2$OSeO$_3$

Tobias Weber, Niclas Heinsdorf, Michal Stekiel et al. (+3 more)

Inelastic neutron scattering in the chiral magnet Cu$_2$OSeO$_3$ reveals strong non-reciprocal effects on magnon propagation at the boundary of the nuclear Brillouin zone. The non-reciprocal response is strongest at a central position between the zone corner and edge mid-point. We explain these results using an effective linear spin-wave model. While directional effects in chiral magnets have so far only been known to exist at low momenta close to the center of the Brillouin zone, the present study shows that non-reciprocity persists at the highest possible reduced momenta. The observed magnons show very little damping within the limits of our experimental resolution, making them of great interest for the fundamental research on compact, high-frequency magnonic applications.
Read the full abstract

All authors Tobias Weber, Niclas Heinsdorf, Michal Stekiel, Paul Steffens, Andreas Schnyder, Christian Pfleiderer

Strongly Correlated Electrons

Parametric Instabilities of Correlated Quantum Matter

Gal Shavit and Gil Refael

Collective bosonic excitations are a fascinating aspect of broken-symmetry correlated phases. A wealth of such phases emerged in tailored moiré heterostructures, where, in addition, new direct knobs of control exist. Our work explores how the associated collective bosonic modes can be directly manipulated and amplified via parametric driving. As we show, parametric driving is closely related to many-body quantum geometry, as it reveals information about the fidelity susceptibility of the underlying ground state with respect to changes in the control knobs of the interacting system. The parametric response hinges on the tunability of the hierarchy of competing ground states, which we show manifests as squeezing of the bosonic mode vacuum. Furthermore, parametrically-driven modes can produce a high-amplitude modulation in the system that could be easily observed, and could also be used to produce a new non-equilibrium prethermal states with different symmetries. We derive a general framework for parametric amplification of collective bosonic modes in broken-symmetry phases, and provide case-studies of current relevance. Elucidating the connection between the dynamics of these excitations and microscopic electronic observables is key to harnessing their immense potential.
Read the full abstract

Quantum Gases

Toward fast, accurate and robust AI prediction of ground states in rotating BEC

Zhizhong Kong, Jerry Zhijian Yang, Cheng Yuan et al. (+1 more)

We propose an unsupervised deep learning approach for computing the ground state (GS) of rotating Bose-Einstein condensation. To minimize the energy under a mass constraint, our approach introduces two key and novel ingredients: a normalized loss function that exactly enforces the mass constraint, and a training strategy named virtual rotation acceleration that is essential for avoiding local minima and guiding the learning process to the correct quantized vortex phase. Extensive numerical experiments demonstrate the proposed approach as an effective and accurate method to predict GS across physical conditions–from slow to fast rotation and from isotropic to anisotropic confinement. Through further distillation, we establish a unified operator network capable of efficiently generalizing physical parameters across different phases. It enables rapid GS predictions while correctly capturing phase transitions and is applied for inverse problems.
Read the full abstract

All authors Zhizhong Kong, Jerry Zhijian Yang, Cheng Yuan, Xiaofei Zhao

Strongly Correlated Electrons

Topological and Trivial Valence-Bond Orders in Higher-Spin Kitaev Models

Xing-Yu Zhang, Qi Yang, Philippe Corboz et al. (+2 more)

We investigate the quantum phases of higher-spin Kitaev models using tensor network methods. Our results reveal distinct bond-ordered phases for spin-1, spin-$\tfrac{3}{2}$, and spin-2 models. In all cases, we find translational symmetry breaking with unit cells being tripled by forming valence-bond orders. However, these three phases are distinct, forming plaquette order, topological dimer order, and non-topological dimer order, respectively. Our findings are based on a cross-validation between variational two-dimensional tensor network calculations: an unrestricted exploration of symmetry-broken states versus the detection of symmetry breaking from cat-state behavior in symmetry-restricted states. The origin of different orders can also be understood from a theoretical analysis. Our work sheds light upon the interplay between topological and symmetry-breaking orders as well as their detection via tensor networks.
Read the full abstract

All authors Xing-Yu Zhang, Qi Yang, Philippe Corboz, Jutho Haegeman, Yuchi He

Soft Condensed Matter · Cross-listed from physics.app-ph

Entanglement-driven responses through multiscale 3D-printed knits

Bradley Cline, Catherine Bai, Sehui Jeong et al. (+5 more)

For their resilience and toughness, filamentous entanglements are ubiquitous in both natural and engineered systems across length scales, from polymer-chain- to collagen-networks and from cable-net structures to forest canopies. Textiles are an everyday manifestation of filamentous entanglement: the remarkable resilience and toughness in knitted fabrics arise predominately from the topology of interlooped yarns. Yet most architected materials do not exploit entanglement as a design primitive, and industrial knitting fixes a narrow set of patterns for manufacturability. Additive manufacturing has recently enabled interlocking structures such as chainmail, knot and woven assemblies, hinting at broader possibilities for entangled architectures. The general challenge is to treat knitting itself as a three-dimensional architected material with predictable and tunable mechanics across scales. Here, we show that knitted architectures fabricated additively can be recast as periodic entangled solids whose responses are both fabric-like and programmable. We reproduce the characteristic behavior of conventional planar knits and extend knitting into the third dimension by interlooping along three orthogonal directions, yielding volumetric knits whose stiffness and dissipation are tuned by prescribed pre-strain. We propose a simple scaling that unifies the responses across stitch geometries and constituent materials. Further, we realize the same topology from centimeter to micrometer scales, culminating in the fabrication of what is, to our knowledge, the smallest knitted structure ever made. By demonstrating 3D-printed knits can be interpreted both as a traditional fabric, as well as a novel architected material with defined periodicity, this work establishes the dual nature of entangled filaments and paves the way towards a new form of material architectures with high degrees of entanglement.
Read the full abstract

All authors Bradley Cline, Catherine Bai, Sehui Jeong, Ling Xu, Yue Wang, James U. Surjadi, Carlos M. Portela, Tian Chen

Mesoscale and Nanoscale Physics

The ideal limit of rhombohedral graphene: Dynamical skyrmion lattices and their excitations

Tixuan Tan, Patrick J. Ledwith and Trithep Devakul

We introduce an interacting ideal limit of rhombohedral graphene in which interactions spontaneously generate a correlated Chern insulator. Our analysis reveals that this Chern insulator can be understood as a layer-pseudospin skyrmion lattice stabilized by electronic interactions, and that it gives rise to genuine skyrmion lattice physics, complete with dynamics. This dynamical skyrmion lattice naturally leads to experimentally measurable consequences. In particular, we identify new collective excitations corresponding to chiral shape deformations of the skyrmions, and propose a new positively charged quasiparticle, the skyrmion vacancy. These results establish a qualitatively new form of moiré Chern physics in rhombohedral graphene: an interaction-generated skyrmion lattice whose skyrmions are dynamical low-energy degrees of freedom.
Read the full abstract

Materials Science

Coexistence of Ferroelectric and Relaxor-like Phases in a Multiferroic Solid Solution (1-x)Pb(Fe$_{1/2}$Nb$_{1/2}$)O$_3$-xPbMnO$_3$

Anna N. Morozovska, Victor N. Pavlikov, Yuriy O. Zagorodniy et al. (+7 more)

Experimental and theoretical studies of unusual polar, dielectric and magnetic properties of room temperature multiferroics, such as perovskites Pb(Fe$_{1/2}$Nb$_{1/2}$)O$_3$ (PFN) and Pb(Fe$_{1/2}$Ta$_{1/2}$)O$_3$ (PFT), are very important. We study the phase composition, dielectric, ferroic properties of the solid solutions PFN and PFT substituted with 5, 10, 15, 20 and 30 % of Mn ions prepared by the solid-state synthesis. The XRD analysis confirmed the perovskite structure of sintered ceramics. Electric measurements revealed the ferroelectric-type hysteresis of electric charge in pure PFN ceramics and in PFN ceramics substituted with (10 - 30)% of Mn. At the same time, the PFN-5% Mn ceramics did not show any ferroelectric properties due to very high conductivity.Temperature dependences of the dielectric permittivity of PFN-10% Mn and PFN-15% Mn ceramics have two pronounced maxima, one of which is relatively sharp and has a weak frequency dispersion; another is diffuse and has a strong frequency dispersion. A further increase in the Mn content up to 20% leads to the right shift in the paraelectric-ferroelectric phase transition temperature, as well as to the strong suppression of the second wide maximum, which transforms into a small diffuse shoulder. An increase in the Mn substitution up to 30% leads to a significant decrease in the dielectric permittivity, left shift of its maximum, and induces a pronounced frequency dispersion of the paraelectric-ferroelectric transition temperature, which is inherent to relaxor-like ferroelectrics.Comparison of the model with experiments reveal the coexistence of the ordered ferroelectric-like and disordered relaxor-like phases in the multiferroic solid solutions PFN-Mn and PFT-Mn.
Read the full abstract

All authors Anna N. Morozovska, Victor N. Pavlikov, Yuriy O. Zagorodniy, Iryna V. Kondakova, Oleksandr S. Pylypchuk, Andrii V. Bodnaruk, Oksana V. Leshchenko, Myroslav V. Karpets, Roman O. Kuzian, Eugene A. Eliseev

Strongly Correlated Electrons

Reduced Density Matrices Through Machine Learning

Awwab A. Azam, Lexu Zhao and Jiabin Yu

$n$-particle reduced density matrices ($n$-RDMs) play a central role in understanding correlated phases of matter, but their calculation is often computationally inefficient for strongly-correlated states at large system sizes. In this work, we use neural network (NN) architectures to accelerate and even predict $n$-RDMs for large systems. Our underlying intuition is that, for gapped states, $n$-RDMs are often smooth functions over the Brillouin zone (BZ) and are therefore interpolable, allowing NNs trained on small-size systems to predict large-size ones. Building on this, we devise two NNs: (i) a self-attention NN that maps random RDMs to physical ones, and (ii) a Sinusoidal Representation Network (SIREN) that directly maps momentum-space coordinates to RDM values. We test the NNs on RDMs in three 2D models: the pair-pair correlation functions of the Richardson model of superconductivity, the translationally-invariant Hartree-Fock (HF) 1-RDM in a four-band repulsive model, and the translation-breaking HF 1-RDM in the half-filled Hubbard model. We find that a SIREN trained on a $6\times 6$ momentum mesh and a SIREN trained on $4$ tilted meshes (each of which has $12$ momentum points) can predict the $18\times 18$ pair-pair correlation function with a relative accuracy of $94.29\%$ and $93.77\%$, respectively. NNs trained on $6\times 6$ and $8\times 8$ meshes provide high-quality initial guesses for $50\times 50$ translation-invariant HF and $30\times 30$ fully translation-breaking-allowed HF, reducing the required number of iterations by up to $91.63\%$ and $92.78\%$, respectively, compared to random initializations. Our results illustrate the potential of NN-based methods for interpolable $n$-RDMs, which might open a new avenue for future research on strongly correlated phases.
Read the full abstract

Strongly Correlated Electrons

Spatio-temporal migration of antiferromagnetic domain walls in Sr2IrO4

Ian Robinson, David Yang, Ross Harder et al. (+18 more)

By laser pump-probe time-resolved coherent magnetic X-ray diffraction imaging, we have measured the migration velocity of antiferromagnetic domain walls in the Mott insulator Sr2IrO4 at 100 K. During the laser-induced demagnetization, we observe domain walls moving at 3x10^6 m/s, significantly faster than acoustic velocities. This is understood to arise from a purely electronic spin contribution to the magnetic structure without any role for coupling to the crystal lattice.
Read the full abstract

All authors Ian Robinson, David Yang, Ross Harder, Dina Sheyfer, Longlong Wu, Jack Griffiths, Emil Bozin, Mark P. M. Dean, Jialun Liu, Hengdi Zhao, Gang Cao, Angel Rodriguez-Fernandez, Jan-Etienne Pudell, Roman Shayduk, James Wrigley, Alexey Zozulya, Rustam Rysov, Aliaksandr Leonau, Ulrike Boesenberg, Joerg Hallmann, Anders Madsen

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

Effect of shape on void growth: A coupled Extended Finite Element Method (XFEM) and Discrete Dislocation Plasticity (DDP) study

Muhammad Usman, Sana Waheed and Aamir Mubashar

Voids are one of the many material defects present at the microscopic length scale. They are primarily responsible for the formation of cracks and hence contribute to ductile fracture. Circular voids tend to deform into elliptical voids just before their coalescence to form cracks. The principle aim of this study is to investigate the effect of void shape on the micro-mechanism of void growth by using Discrete Dislocation Plasticity simulations. For voided crystals, conventional DDP produces a continuous slip step throughout the material even if a dislocation escapes from a non-convex domain. To overcome this issue, the Extended Finite Element Method (XFEM) is used here to incorporate the displacement discontinuity. Different aspect ratios of elliptical voids are considered under uniaxial and biaxial deformation boundary conditions. The results suggest that voids having the largest surface area tend to have maximum growth rate as compared to void with lower surface area, i.e. "larger is faster". Under biaxial loading, a higher magnitude of strain hardening, and void growth rate are observed as compared to uniaxial loading. The results also suggest that the orientation of slip planes as well as voids, affect the overall plastic behavior of the voided-ductile material. Furthermore, circular void tends to induce minimum growth rate but have the maximum strain hardening effect as compared to other void shapes under both loading conditions. The results of this study provide a deeper understanding of ductile fracture with applications in manufacturing industry, aerospace industry and in the design of nano/micro-electromechanical devices i.e. NEMS/MEMS.
Read the full abstract

Statistical Mechanics · Cross-listed from math.PR

Decoupling of clusters in independent sets in a percolated hypercube

Mriganka Basu Roy Chowdhury, Shirshendu Ganguly and Vilas Winstein

Independent sets in graphs are sets of vertices containing no neighbors, and they represent a canonical spin system with hardcore constraints. Of particular interest is the setting of the boolean hypercube, where counting independent sets was the original motivator for Sapozhenko's famous graph container method. A modern perspective on such problems is to consider the effect of disorder, and the study of independent sets in random subgraphs of the hypercube obtained via bond percolation with parameter $p$ was initiated by Kronenberg and Spinka. They employed tools from statistical mechanics to obtain detailed information about the moments of the number of independent sets (now a random variable), and posed many interesting questions. Previous work by the authors addressed many of these questions in the regime $p \geq \frac{2}{3}$, where the behavior is relatively simple and can be modeled well by a related family of independent particles. As $p$ decreases, though, typical independent sets become larger and feature more intricate clustering behavior. In the present article we overcome many of the challenges presented by this phenomenon and analyze the model for all $p> 0.465$. We obtain a sharp in-probability approximation for the number of independent sets in the percolated hypercube in terms of explicit random variables, as well as provide a sampling algorithm. Note that this shows, curiously, that $p = \frac{1}{2}$ is not a natural barrier for this problem unlike in many other problems where it appears as a point of a phase transition. A key contribution of this work is the introduction of a new probabilistic framework to handle the clustering behavior for these low values of $p$. Although our analysis is restricted to $p > 0.465$, our arguments are expected to be helpful for studying this model at even lower values of $p$, and possibly for other related problems.
Read the full abstract