Strongly Correlated Electrons
Interacting type-II semi-Dirac quasiparticles
Mohamed M. Elsayed, Taras I. Lakoba and Valeri N. Kotov
Type-II semi-Dirac
fermions in two dimensions have been proposed to describe topologically nontrivial low-energy excitations in titanium/vanadium
oxide heterostructures. These quasiparticles appear at the merger of three Dirac cones, resulting in a non-zero Berry phase. We find, by employing Hartree-Fock, renormalization group and Random Phase Approximation (RPA) techniques, that the spectrum is very sensitive to long-range electron-electron interactions and can undergo a profound transformation. Our results indicate that at the topological phase boundary, long-range correlations stabilize a hybrid electronic phase displaying both Dirac and type-II semi-Dirac qualities, with physical characteristics exhibiting continuously varying critical exponents as a function of the
Fermi energy; for example Landau levels in a
magnetic field vary with the energy scale: $|\varepsilon_n(B)|\sim (nB)^{1/2} \rightarrow (nB)^{3/4}, n\in \mathbb{N}_0$. The quasiparticle spectrum evolves, driven by interactions, from anisotropic Dirac dispersion at the lowest energies, towards the characteristic type-II semi-Dirac boomerang shape as the energy increases. The corresponding density of states concomitantly varies between linear and power one third ($\rho(\varepsilon) \sim |\varepsilon| \rightarrow |\varepsilon|^{1/3}$). The crossover scale is controlled by the interaction strength $\alpha = e^2/(\hbar v)$ and the specifics of the effective interacting
Hamiltonian.
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Materials Science
Extraction of a structural short-range order descriptor from nanobeam electron diffraction patterns using a transfer learning approach
Junjie Wu and Timothy J. Rupert
Amorphous solids exhibit structural short-range order despite lacking long-range crystalline order, with this structural descriptor found to be important for determining mechanical properties. Nanobeam electron diffraction offers a potential route for experimental characterization of structural short-range order, yet efforts to date have been primarily qualitative in nature. In this work, machine learning approaches based on transfer learning are used to enable quantitative analysis of nanobeam electron diffraction data from amorphous solids. A ResNet-18 model is trained on simulated diffraction patterns taken from different locations within simulated metallic glasses and amorphous grain boundary complexions in the Cu-Zr
alloy system that were created with hybrid molecular dynamics and Monte Carlo simulations. The disorder parameter is found to be a superior target structural descriptor compared to traditional Voronoi indices for this task. The model achieves a low validation mean absolute error across diffraction patterns corresponding to different interaction volumes, demonstrating excellent performance and potential transferability. Testing was performed using other simulated nanobeam electron diffraction data as well as experimental nanobeam electron diffraction patterns, showing that the model can reliably capture spatial variations in local structural state. As a whole, this framework is able to overcome the challenges in the quantitative experimental characterization of structural short-range order, enabling improved characterization of amorphous solids and the exploration of structure-property relationships.
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Strongly Correlated Electrons
Influence of Markovianity and self-consistency on time-resolved spectral functions of driven quantum systems
Thomas Blommel, M. Rey Lambert, Michael A. Kurniawan et al. (+2 more)
We present a systematic comparison of the real-time Dyson expansion (RTDE) with established non-
equilibrium Green's function approaches for simulating driven, interacting
quantum systems. Focusing on density
matrix dynamics, time-off-diagonal Green's functions, and time-resolved photoemission spectra, we
benchmark RTDE against fully self-consistent Kadanoff-Baym equation (KBE) calculations, the generalized Kadanoff-Baym ansatz (GKBA), and exact diagonalization for small systems using second order many-body perturbation theory. Using a driven two-band Hubbard model, we show that mean-field single particle density
matrix trajectories provide a reliable baseline for RTDE across a broad range of interaction strengths and excited-carrier populations. Further, RTDE accurately captures correlation effects in the Green's functions, including long-lived oscillations and revivals that are strongly suppressed by the overdamping inherent to self-consistent KBE schemes. As a consequence, RTDE resolves rich non-
equilibrium spectral structure in time-resolved photoemission, such as interaction- and population-dependent quasiparticle splittings and bandgap renormalization, which are largely washed out in self-consistent approaches, yet are present in the exact solutions. Our results demonstrate that RTDE bridges the gap between mean-field propagation and full two-time KBE simulations, retaining favorable linear scaling while capturing essential dynamical correlations relevant for ultrafast spectroscopy.
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All authors Thomas Blommel, M. Rey Lambert, Michael A. Kurniawan, Annabelle Canestraight, Vojtech Vlcek
Soft Condensed Matter · Cross-listed from physics.flu-dyn
Reviving the Suspension Balance Model
Mu Wang, Tingtao Zhou and John F. Brady
The Suspension Balance Model (SBM) [J. Fluid Mech. 275, 157 (1994)] for two-phase flows uses the momentum balance of the particle phase as a closure for the particle flux, showing that particle migration is driven by the divergence of the particle-phase stress. The underlying basis of this model was challenged by Nott~et~al.\ [Phys. Fluids 23, 043304 (2011)] where the authors argued that the hydrodynamic contributions to the suspension stress should not appear in the particle-phase momentum balance, being replaced by a different particle-phase stress. The particle-phase stress proposed by Nott~et~al., while mathematically correct, involves the partitioning of the (non-pairwise-additive) hydrodynamic forces, and care is needed to understand how the force on a chosen particle is affected by a second particle. We show by a simple two-particle calculation what is the proper partitioning, and show that it is consistent thermodynamically and gives the correct
equilibrium osmotic pressure of Brownian colloids. Using Stokesian Dyanmics suspension rheology, we quantitatively demonstrate that the hydrodynamic contribution to the suspension stress is virtually identical to particle-phase stress; the only difference is that the isolated single-particle hydrodynamic stress contribution – the Einstein viscosity correction – must be removed from the suspension stress when used to predict particle flux. Our results validate a key assumption of the SBM and therefore revive its physical foundation.
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Materials Science
Accelerated Inorganic Electrides Discovery by Generative Models and Hierarchical Screening
Shuo Tao and Qiang Zhu
Electrides are exotic compounds in which excess electrons occupy interstitial regions of the
crystal lattice and serve as anions, exhibiting exceptional properties such as low work function, high electron mobility, and strong catalytic activity. Although they show promise for diverse applications, identifying new electrides remains challenging due to the difficulty of achieving energetically favorable electron localization in
crystal cavities. Here, we present an accelerated materials discovery framework that combines physical principles,
diffusion-based materials generation with hierarchical thermodynamic and electronic structure screening. Using this workflow, we systematically explored 1,510 binary and 6,654 ternary chemical compositions containing excess valence electrons from electropositive alkaline, alkaline-earth, and early transition metals, and then filtered them with a high throughput validation on both thermodynamical stability and electronic structure analysis. As a result, we have identified 264 new electron rich compounds within 0.05 eV/atom above the convex hull at the density functional theory (DFT) level, including 13 thermodynamically stable electrides. Our approach demonstrates a generalizable strategy for targeted materials discovery in a vast chemical space.
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Mesoscale and Nanoscale Physics
Rocket-like dynamics of ferrimagnetic domain walls in graded materials
P. Diona, S. Artyukhin and L. Maranzana
Domain wall motion underpins emerging spintronic technologies, such as high-speed racetrack devices and THz logic, and accelerating walls quickly is a key challenge on the path to faster devices. Recent experimental advances introduced
magnetic materials with non-uniform composition, allowing angular momentum compensation points and fast domain wall motion, although acceleration of domain walls in these materials remains poorly understood. Here, we show that spatial variation of exchange and anisotropy not only pushes the wall towards lower wall surface tension region, but also modifies its inertial mass, giving rise to a variable-mass relativistic dynamics. We find another force, originating from the
magnon velocity gradient, that dominates as the wall velocity approaches the
magnon speed. Our results identify domain walls in nonuniform magnets as a playground for relativistic physics with variable mass and limiting speed.https://info.arxiv.org/help/prep#comments
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Statistical Mechanics · Cross-listed from quant-ph
Jonathan Jeffrey, Lucien Gandarias, Monika Schleier-Smith et al. (+1 more)
We propose a framework for preparing
quantum states with a
holographic entanglement structure, in the sense that the
entanglement entropies are governed by minimal surfaces in a chosen bulk geometry. We refer to such
entropies as
holographic because they obey a relation between
entropies and bulk minimal surfaces, known as the Ryu-Takayanagi (RT) formula, that is a key feature of
holographic models of
quantum gravity. Typically in such models, the bulk geometry is determined by solving Einstein's equations. Here, we simply choose a bulk geometry, then discretize the geometry into a coupling graph comprising bulk and boundary nodes. Evolving under this graph of interactions and measuring the bulk nodes leaves behind the desired pure state on the boundary. We numerically demonstrate that the resulting
entanglement properties approximately reproduce the predictions of the Ryu-Takayanagi formula in the chosen bulk geometry. We consider graphs associated with
hyperbolic disk and wormhole geometries, but the approach is general. We also introduce a procedure for decorating the graph which, when applied to the
hyperbolic disk, yields a genuine CFT ground state with power-law correlations but which only partially obeys RT. The minimal ingredients in our proposal involve only Gaussian operations and measurements and are readily implementable in photonic and cold-atom platforms.
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All authors Jonathan Jeffrey, Lucien Gandarias, Monika Schleier-Smith, Brian Swingle
Quantum Gases · Cross-listed from quant-ph
Polaron-Polaritons in Subwavelength Arrays of Trapped Atoms
Kristian Knakkergaard Nielsen, Lukas Wangler, David Castells-Graells et al. (+4 more)
Subwavelength arrays of atoms trapped in optical
lattices or tweezers are inherently susceptible to deformations: Optomechanical forces displace atoms within their trapping potential and produce
lattice distortions, which in turn modify the optical response of the array. We show that this optomechanical coupling hybridizes collective atomic excitations (polaritons) with
phonons, forming polaron-polaritons – the fundamental quasiparticles governing light-matter interactions in arrays of trapped atoms. Using analytical polaron theory and numerical simulations, we find that: (1)
phonons can strongly enhance the decay of subradiant states, but also enable their efficient excitation; (2) transport of dark excitations remains remarkably robust even at low trap frequencies, except when a polariton can resonantly scatter
phonons; and (3) motion reduces the reflectivity of a two-dimensional atomic mirror; by identifying design principles that mitigate this degradation, we recover reflectivity above 99% under realistic conditions. Our findings lay the foundation for analyzing motional effects in key applications and suggest new ways to harness them in state-of-the-art experiments.
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All authors Kristian Knakkergaard Nielsen, Lukas Wangler, David Castells-Graells, J. Ignacio Cirac, Ana Asenjo-Garcia, Daniel Malz, Cosimo C. Rusconi
Materials Science · Cross-listed from physics.chem-ph
Better without U: Impact of Selective Hubbard U Correction on Foundational MLIPs
Thomas Warford, Fabian L. Thiemann and Gábor Csányi
The training of foundational machine learning interatomic potentials (fMLIPs) relies on diverse databases with energies and forces calculated using ab initio methods. We show that fMLIPs trained on large
datasets such as MPtrj, Alexandria, and OMat24 encode inconsistencies from the Materials Project's selective use of the Hubbard U correction, which is applied to certain transition metals only if O or F atoms are present in the simulation
cell. This inconsistent use of +U creates two incompatible potential-energy surfaces (PES): a lower-energy GGA surface and a higher-energy GGA+U one. When trained on both, MLIPs interpolate between them, leading to systematic underbinding, or even spurious repulsion, between U-corrected metals and oxygen- or fluorine-containing species. Models such as MACE-OMAT and -MPA exhibit repulsion between U-corrected metals and their
oxides, limiting their value for studying catalysis and oxidation. We link the severity of this pathology to the oxygen number density in U-corrected training configurations. This explains why OMAT-trained models are most affected and suggests the issue might worsen as expanding future
datasets increasingly include configurations with low oxygen content, such as those generated through combinatorial exploration of multi-element or defect-containing systems. Our simple per-U-corrected-atom shift aligns PBE+U and PBE energies for identical structures, yielding a smoother PES compared to existing correction schemes, which target phase diagram accuracy. As a result, models trained on
datasets with our shift applied exhibit smaller mean absolute errors for the adsorption energies of oxygen on U-corrected elemental slabs. Since
datasets omitting +U entirely (e.g. MatPES, MP-ALOE) avoid these pathologies, we recommend excluding +U in future fMLIP
datasets. For existing
datasets, our post-hoc correction provides a low-cost improvement.
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Materials Science
Field-Induced Ferroelectric Phase Transition Dynamics in PMN-PT compositions near the Morphotropic Phase Boundary
Shivjeet Chanan, Joseph Kerchenfaut, Eduard Illin et al. (+1 more)
The dynamical behavior of field-induced ferroelectric phase transitions in compositions of PbMg1/3Nb2/3O3(1-x)-PbTiO3(x) (PMN-PT) near the morphotropic phase boundary (MPB) was investigated using several electric-field application protocols. Our results show that PMN-PT compositions near the MPB exhibit phase-transition dynamics that differ markedly from those far below the MPB. We demonstrate that electric-field history significantly affects the field-induced transition temperature Tc, zero-field-cooling (ZFC) delay time tau_ZFC, and induced polarization Pc gained or lost during the transition. Furthermore, under specific field-temperature conditions, PMN-PT retains a
memory of its electric-field history and uses it to kinetically accelerate ferroelectric ordering. We propose an explanation for the differences in phase-transition dynamics between MPB-proximal and MPB-distant compositions, contextualized within prior literature.
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All authors Shivjeet Chanan, Joseph Kerchenfaut, Eduard Illin, Eugene V. Colla
Strongly Correlated Electrons
Classification of non-Fermi liquids and universal superconducting fluctuations
Shubham Kukreja, Dawson M. Willerton and Sung-Sik Lee
In
quantum critical metals, a plethora of different non-
Fermi liquids arises depending on the nature of critical fluctuations coupled to
Fermi surfaces. In this paper, we classify non-
Fermi liquids that arise from q=0 critical fluctuations and characterize their universal superconducting fluctuations. The essential tool is the projective fixed points, which generalizes the notion of fixed points to fixed trajectories that take into account the incessant running of the
Fermi momentum under the renormalization group flow. Based on the
topology of bundles of projective fixed points, non-
Fermi liquids are first grouped into seven superuniversality classes. Each superuniversality class includes multiple universality classes, which are further classified by the universal pairing interactions and emergent
symmetries. Despite the pairing interaction generated by critical fluctuations, some non-
Fermi liquids remain stable down to zero temperature due to the incoherence of excitations and the lack of scale invariance caused by
Fermi momentum. Depending on the strength and span of the universal pairing interaction in momentum space, the emergent
symmetry of non-
Fermi liquids may or may not be lower than that of
Fermi liquids. In non-
Fermi liquids that become
superconductors at low temperatures, the universal data of the parent metal determine the lower bound for the superconducting transition temperature and the associated pairing
symmetry. In superuniversality classes that contain non-
Fermi liquids prone to non-s-wave superconducting instabilities, the critical angular momentum above which pairing instability becomes inevitable is sensitive to the
Fermi momentum, and the associated superconducting transition temperature oscillates as a function of the density. We use physical examples, as well as a toy model, to elucidate the universal low-energy physics of all superuniversality classes.
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Superconductivity
Benjamin Geisler, Philip M. Dee, James J. Hamlin et al. (+3 more)
Superconducting materials are of significant technological relevance for a broad range of applications, and intense research efforts aim at enhancing the critical temperature $T_{c}$. Intriguingly, while numerous studies have explored different computational and machine-learning routes to predict $T_{c}$, the fundamental role of the critical
magnetic field has so far been overlooked. Here we open a new frontier in
superconductor discovery by presenting a consistent computational database of critical fields $H_{c}$, $H_{c1}$, and $H_{c2}$ for over 7300 electron-
phonon-paired
superconductors covering distinct materials classes. A theoretical framework is developed that combines $\alpha^2F(\omega)$ spectral functions and highly accurate
Fermi surfaces from density functional theory with clean-limit Eliashberg theory to obtain the coherence lengths, London penetration depths, and Ginzburg-Landau parameters. We discover an unexpectedly large number of Type-I
superconductors and show that larger unit
cells generically support higher critical fields and Type-II behavior. We identify the importance of going beyond BCS theory by including strong-coupling corrections to the superconducting gap and electron-
phonon renormalizations of the effective mass for predictions of critical fields across materials. These results provide a framework for foundational AI models that realize the concept of inverse materials design for high-$T_{c}$ and high-critical-field
superconductors.
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All authors Benjamin Geisler, Philip M. Dee, James J. Hamlin, Gregory R. Stewart, Richard G. Hennig, P.J. Hirschfeld
Strongly Correlated Electrons
Ultrafast Decoherence of Charge Density Waves in K$_{0.3}$MoO$_{3}$
Rafael T. Winkler, Larissa Boie, Yunpei Deng et al. (+20 more)
Recent works have suggested that transient suppression of a charge density wave (CDW) by an ultra-short excitation can lead to an inversion of the CDW phase. We experimentally investigate the dynamics of the CDW in K$_{0.3}$MoO$_{3}$ by time resolved x-ray diffraction after excitation with optical pulses. Our results indicate a transient inversion of the CDW phase close to the surface that evolves into a highly disordered state in less than one picosecond. Numerical simulations solving the Ginzburg-Landau equation including disorder from strong pinning defects reproduce our main observations. Our findings highlight the critical role of disorder in schemes for coherent control in condensed matter systems.
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All authors Rafael T. Winkler, Larissa Boie, Yunpei Deng, Matteo Savoini, Serhane Zerdane, Abhishek Nag, Sabina Gurung, Davide Soranzio, Tim Suter, Vladimir Ovuka, Janine Zemp, Elsa Abreu, Simone Biasco, Roman Mankowsky, Edwin J. Divall, Alexander R. Oggenfuss, Mathias Sander, Christopher Arrell, Danylo Babich, Henrik T. Lemke, Urs Staub, Jure Demsar, Steven L. Johnson
Strongly Correlated Electrons
Competing Ordering Modes in the Distorted Quantum Kagome Material Clinoatacamite Cu$_2$Cl(OH)$_3$
L. Stödter, C. Kastner, H. O. Jeschke et al. (+20 more)
We have studied the
magnetic properties of clinoatacamite Cu$_2$Cl(OH)$_3$, the parent compound of the
quantum spin liquid candidate herbertsmithite and a longstanding puzzle among frustrated
quantum magnets. As we reveal using density-functional theory, clinoatacamite belongs to the class of distorted kagome antiferromagnets with the kagome plane being embedded into a low-
symmetry crystal structure. By means of thermodynamic measurements,
muon spin rotation/relaxation as well as
neutron diffraction on single
crystals, we find in zero
magnetic field complex behavior below $T_\mathrm{I}$ = 18.1 K which unfolds in three temperature regions I-III. We propose this complexity in multicritical clinoatacamite to arise from the competition of
antiferromagnetic ordering modes from the underconstrained
manifold of modes, which can lead to a metamagnetic texture in zero field.
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All authors L. Stödter, C. Kastner, H. O. Jeschke, M. Reehuis, E. Chan, M.-H. Lemée-Cailleau, K. Beauvois, B. Ouladdiaf, F. Yokaichiya, F. Bert, T. J. Hicken, J. A. Krieger, H. Luetkens, J. L. Allen, R. Feyerherm, M. Tovar, D. Menzel, A. U. B. Wolter, B. Büchner, K. C. Rule, F. J. Litterst, U. K. Rößler, S. Süllow
Materials Science · Cross-listed from physics.chem-ph
StochasticGW-GPU: rapid quasi-particle energies for molecules beyond 10000 atoms
Phillip S. Thomas, Minh Nguyen, Dimitri Bazile et al. (+6 more)
$\mathtt{StochasticGW}$ is a code for computing accurate Quasi-Particle (QP) energies of molecules and material systems in the GW approximation. $\mathtt{StochasticGW}$ utilizes the
stochastic Resolution of the Identity (sROI) technique to enable a massively-parallel implementation with computational costs that scale semi-linearly with system size, allowing the method to access systems with tens of thousands of electrons. We introduce a new implementation, $\mathtt{StochasticGW-GPU}$, for which the main bottleneck steps have been ported to GPUs and which gives substantial performance improvements over previous versions of the code. We showcase the new code by computing band gaps of hydrogenated silicon clusters ($\textrm{S}\textrm{i}_{\textrm{x}}\textrm{H}_{\textrm{y}}$) containing up to 10001 atoms and 35144 electrons, and we obtain individual QP energies with a statistical precision of better than $\pm0.03$ eV with times-to-solution on the order of minutes.
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All authors Phillip S. Thomas, Minh Nguyen, Dimitri Bazile, Tucker Allen, Barry Y. Li, Wenfei Li, Mauro Del Ben, Jack Deslippe, Daniel Neuhauser
Materials Science · Cross-listed from cs.LG
MADE: Benchmark Environments for Closed-Loop Materials Discovery
Shreshth A Malik, Tiarnan Doherty, Panagiotis Tigas et al. (+4 more)
Existing
benchmarks for computational materials discovery primarily evaluate static predictive tasks or isolated computational sub-tasks. While valuable, these evaluations neglect the inherently iterative and adaptive nature of scientific discovery. We introduce MAterials Discovery Environments (MADE), a novel framework for benchmarking end-to-end autonomous materials discovery pipelines. MADE simulates closed-loop discovery campaigns in which an
agent or
algorithm proposes, evaluates, and refines candidate materials under a constrained oracle budget, capturing the sequential and resource-limited nature of real discovery workflows. We formalize discovery as a search for thermodynamically stable compounds relative to a given convex hull, and evaluate efficacy and efficiency via comparison to baseline
algorithms. The framework is flexible; users can compose discovery
agents from interchangeable components such as generative models, filters, and planners, enabling the study of arbitrary workflows ranging from fixed pipelines to fully agentic systems with tool use and adaptive decision making. We demonstrate this by conducting systematic experiments across a family of systems, enabling ablation of components in discovery pipelines, and comparison of how methods scale with system complexity.
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All authors Shreshth A Malik, Tiarnan Doherty, Panagiotis Tigas, Muhammed Razzak, Stephen J. Roberts, Aron Walsh, Yarin Gal
Strongly Correlated Electrons
Spin-orbit-induced Instability and Finite-Temperature Stabilization of a Triangular-lattice Supersolid
Seongjun Park, Sung-Min Park, Yun-Tak Oh et al. (+2 more)
Geometrically frustrated triangular-
lattice magnets provide fertile ground for realizing intriguing
quantum phases such as
spin supersolids. A common expectation is that
spin-orbit coupling (SOC), which breaks continuous
spin rotational
symmetry, destabilizes these phases by gapping their low-energy modes. Revisiting this assumption, we map out the SOC-field phase diagram of a frustrated triangular-
lattice magnet using
spin-wave theory and infinite density-
matrix renormalization group (iDMRG) simulations. We find that while infinitesimally weak SOC indeed drives a zero-temperature instability of the supersolid by opening a gap, certain supersolid states remain thermodynamically stable at non-zero temperatures. This reveals a previously unrecognized mechanism in which thermal fluctuations counteract SOC to stabilize supersolidity. The resulting finite-temperature supersolids retain key responses, including a
giant magnetocaloric effect, highlighting their potential relevance to real materials. At larger SOC, the system transitions into distinct
magnetic orders, including a skyrmion
lattice, completing a unified phase diagram.
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All authors Seongjun Park, Sung-Min Park, Yun-Tak Oh, Hyun-Yong Lee, Eun-Gook Moon
Strongly Correlated Electrons · Cross-listed from quant-ph
Universal Gates from Braiding and Fusing Anyons on Quantum Hardware
Chiu Fan Bowen Lo, Anasuya Lyons, Dan Gresh et al. (+8 more)
Topological
quantum computation encodes
quantum information in the internal fusion space of non-Abelian anyonic quasiparticles, whose braiding implements logical gates. This goes beyond Abelian topological order (TO) such as the toric code, as its anyons lack internal structure. However, the simplest non-Abelian generalizations of the toric code do not support universality via braiding alone. Here we demonstrate that such minimally non-Abelian TOs can be made universal by treating anyon fusion as a computational primitive. We prepare a 54-
qubit TO wavefunction associated with the smallest non-Abelian group, $S_3$, on Quantinuum's H2
quantum processor. This phase of matter exhibits cyclic anyon fusion rules, known to underpin universality, which we evidence by trapping a single non-Abelian anyon on the
torus. We encode logical qutrits in the nonlocal fusion space of non-Abelian fluxes and, by combining an entangling braiding operation with anyon charge measurements, realize a universal topological gate set and read-out, which we further demonstrate by topologically preparing a magic state. This work establishes $S_3$ TO as simple enough to be prepared efficiently, yet rich enough to enable universal topological
quantum computation.
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All authors Chiu Fan Bowen Lo, Anasuya Lyons, Dan Gresh, Michael Mills, Peter E. Siegfried, Maxwell D. Urmey, Nathanan Tantivasadakarn, Henrik Dreyer, Ashvin Vishwanath, Ruben Verresen, Mohsin Iqbal
Mesoscale and Nanoscale Physics
Topological Acoustic Diode
Ashwat Jain, Wojciech J. Jankowski, M. Mehraeen et al. (+1 more)
We show that certain three-dimensional topological phases can act as acoustic diodes realizing nonlinear odd acoustoelastic effects. Beyond uncovering topologically-induced anomalous acoustic second-harmonic generation and rectification, we demonstrate how such nonlinear responses are uniquely captured by the momentum-space nonmetricity tensor in the
quantum state
Hilbert-space geometry. In addition to completing the classification of
quantum geometric observables in the quadratic response regime, our findings reveal unexplored avenues for experimental realizations of acoustic diodes using effective $\theta$
vacua of
axion insulators adaptable for topological engineering applications.
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All authors Ashwat Jain, Wojciech J. Jankowski, M. Mehraeen, Robert-Jan Slager
Mesoscale and Nanoscale Physics
Spin angular momentum transfer in the Einstein-de Haas effect
Xin Nie, Wenhao Luo, Kun Cao et al. (+1 more)
We investigate
spin angular momentum transfer in the Einstein-de Haas effect within prototypical
magnetic crystals, focusing on its partition between
phonons and rigid-body rotation. Using the Eckart frame to decouple local vibrations (
phonons) from rigid-body rotation, we demonstrate that
spin angular momentum is simultaneously transferred into both
phonons and rigid-body rotation in an asymmetric way: rigid-body rotation acquires the dominant share of angular momentum, while
phonons absorb most of the resulting kinetic energy. This divergent transfer of angular momentum and energy identifies
phonons as direct and indispensable participants in the Einstein-de Haas dynamics. Furthermore, we find that pseudo-dipolar anisotropy and Dzyaloshinskii-Moriya interaction exert distinct control over the angular momentum transfer. Stronger pseudo-dipolar anisotropy increases the total amount of transferred angular momentum, whereas stronger Dzyaloshinskii-Moriya interaction accelerates the transfer rate and increases the proportion of
phonon angular momentum. Our work clarifies the microscopic picture of the Einstein-de Haas effect and enables targeted angular-momentum control in magneto-mechanical devices.
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All authors Xin Nie, Wenhao Luo, Kun Cao, Dao-Xin Yao
Strongly Correlated Electrons
Self-dual Higgs transitions: Toric code and beyond
Wenjie Ji, Ryan A. Lanzetta, Zheng Zhou et al. (+1 more)
The toric code, when deformed in a way that preserves the self-duality $\mathbb{Z}_2$
symmetry exchanging the electric and
magnetic excitations, admits a transition to a topologically trivial state that spontaneously breaks the $\mathbb{Z}_2$
symmetry. Numerically, this transition was found to be continuous, which makes it particularly enigmatic given the longstanding absence of a continuum field-theoretic description. In this work we propose such a continuum field theory for the transition dubbed the $SO(4)_{2,-2}$ Chern-Simons-
Higgs (CSH) theory. We show that our field theory provides a natural "mean-field" understanding of the phase diagram. Moreover, it can be generalized to an entire series of theories, namely the $SO(4)_{k,-k}$ CSH theories, labeled by an integer $k$. For each $k>2$, the theory describes an analogous transition involving different non-Abelian topological orders, such as the double Fibonacci order ($k=3$) and the $S_3$
quantum double ($k=4$). For $k=1$, we
conjecture that the corresponding CSH transition is in fact infrared-dual to the $3d$ Ising transition, in close analogy with the particle-
vortex duality of a complex scalar.
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All authors Wenjie Ji, Ryan A. Lanzetta, Zheng Zhou, Chong Wang
Strongly Correlated Electrons · Cross-listed from quant-ph
Non-Equilibrium Phase Transition in a Boundary-Driven Dissipative Fermionic Chain
Hao Chen, Wucheng Zhang, Manas Kulkarni et al. (+1 more)
We demonstrate that a boundary-localized periodic (Floquet) drive can induce nontrivial long-range correlations in a non-interacting fermionic chain which is additionally subject to boundary dissipation. Surprisingly, we find that this phenomenon occurs even when the corresponding isolated bulk is in a trivial gapped phase with exponentially decaying correlations. We argue that this boundary-drive induced non-
equilibrium transition (as witnessed through the correlation
matrix) is driven by a resonance mechanism whereby the drive frequency bridges bulk energy gaps, allowing boundary-injected particles and holes to propagate and mediate long-range correlations into the bulk. We also numerically establish that when the drive bridges a particle-hole gap, the induced long-range order scales as a power law with the bulk pairing potential ($\chi \sim \gamma^2$). Our results highlight the potential of localized coherent driving for generating macroscopic order in open
quantum systems.
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All authors Hao Chen, Wucheng Zhang, Manas Kulkarni, Abhinav Prem
Superconductivity
Protection of Unconventional Superconductivity from Disorder
Sofie Castro Holbæk, Morten H. Christensen, Andreas Kreisel et al. (+1 more)
Unconventional superconductivity is a desirable state of matter due to its potential for high transition temperatures $T_{\mathrm{c}}$ and associated favorable superconducting properties. However, the sign-changing nature of the order parameter of unconventional
superconductors renders their condensates fragile to disorder, an inevitability in real materials. We uncover the generic properties of electronic band structures and associated Bloch weights able to support robust unconventional superconductivity. We demonstrate this property in several case studies of the kagome and Lieb
lattices, showing how unconventional
superconductors exhibit unusually weak $T_{\mathrm{c}}$ suppression by disorder, despite featuring fully compensated sign-changing order parameters. We contrast these results with those for unconventional superconductivity on the square and honeycomb
lattices, which are unable to protect the condensates from disorder. Finally, we discuss material candidates for which this effect may be realized.
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All authors Sofie Castro Holbæk, Morten H. Christensen, Andreas Kreisel, Brian M. Andersen
Strongly Correlated Electrons
When does a lattice higher-form symmetry flow to a topological higher-form symmetry at low energies?
Ruizhi Liu, Pok Man Tam, Ho Tat Lam et al. (+1 more)
We study the
lattice version of higher-form
symmetries on tensor-product
Hilbert spaces. Interestingly, at low energies, these
symmetries may not flow to the topological higher-form
symmetries familiar from relativistic
quantum field theories, but instead to non-topological higher-form
symmetries. We present concrete
lattice models exhibiting this phenomenon. One particular model is an $\mathbb{R}$ generalization of the Kitaev honeycomb model featuring an $\mathbb{R}$
lattice 1-form
symmetry. We show that its low-energy effective field theory is a gapless, non-relativistic theory with a non-topological $\mathbb{R}$ 1-form
symmetry. In both the
lattice model and the effective field theory, we demonstrate that the non-topological $\mathbb{R}$ 1-form
symmetry is not robust against local perturbations. In contrast, we also study various modifications of the toric code and their low-energy effective field theories to demonstrate that the compact $\mathbb{Z}_2$
lattice 1-form
symmetry does become topological at low energies unless the
Hamiltonian is fine-tuned. Along the way, we clarify the rules for constructing low-energy effective field theories in the presence of multiple superselection sectors. Finally, we argue on general grounds that non-compact higher-form
symmetries (such as $\mathbb{R}$ and $\mathbb{Z}$ 1-form
symmetries) in
lattice systems generically remain non-topological at low energies, whereas compact higher-form
symmetries (such as $\mathbb{Z}_{n}$ and $U(1)$ 1-form
symmetries) generically become topological.
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All authors Ruizhi Liu, Pok Man Tam, Ho Tat Lam, Liujun Zou
Disordered Systems and Neural Networks
Hidden localization transitions in canonically rotated Aubry-André models
Pasquale Marra
Anderson localization is a phase transition between a "metallic phase", where wavefunctions are extended and delocalized in space, and an "insulating phase", where wavefunctions are completely localized. These transitions are driven by uncorrelated or quasiperiodic disorder, e.g., in the case of the Aubry-André model. Here, I consider a family of
Hamiltonians that generalizes the Aubry-André model, obtained by replacing the position and momentum operators with an arbitrary pair of canonically conjugate operators. These models exhibit a hidden localization transition. The system transitions between phases where wavefunctions are either localized or delocalized with respect to the new canonically conjugate operators, acting as an
insulator or metal in this rotated space. These canonically conjugate operators can be taken as a linear combination of position and momentum, corresponding to a "rotation" in the abstract space of canonical operators. In this case, the hidden localization transition is signaled by the simultaneous vanishing of both the inverse participation ratio (IPR) and the normalized participation ratio (NPR) in the position and momentum space in the thermodynamic limit. This identifies the emergence of multifractal states that are neither fully extensive nor localized on the
lattice. Hence, the states exhibit a multifractal dimension at the hidden phase transition, while remaining extended (i.e., one-dimensional) in both momentum and position everywhere else in the parameter space. Surprisingly, I found that at the phase transition, this model
Hamiltonian coincides with the
lattice Hamiltonian of a massless Dirac
fermion in a curved spacetime background, indicating an unexpected relation between localization transitions and analog
gravity.
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Strongly Correlated Electrons
Quench spectroscopy of amplitude modes in a one-dimensional critical phase
Hyunsoo Ha, David A. Huse and Rhine Samajdar
We investigate the emergence of an amplitude (
Higgs-like) mode in the gapless phase of the $(1+1)$D XXZ
spin chain. Unlike conventional settings where amplitude modes arise from spontaneous
symmetry breaking, here, we identify a
symmetry-preserving underdamped excitation on top of a Luttinger-
liquid ground state. Using nonequilibrium quench spectroscopy, we demonstrate that this mode manifests as oscillations of U(1)-symmetric observables following a sudden quench. By combining numerical simulations with Bethe-ansatz analyses, we trace its microscopic origin to specific families of string excitations. We further discuss experimental pathways to detect this mode in easy-plane
quantum magnets and programmable
quantum simulators. Our results showcase the utility of
quantum quenches as a powerful tool to probe collective excitations, beyond the scope of linear response.
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Statistical Mechanics · Cross-listed from quant-ph
Double-Bracket Master Equations: Phase-Space Representation and Classical Limit
Ankit W. Shrestha, Budhaditya Bhattacharjee and Adolfo del Campo
We systematically investigate master equations involving double-bracket dissipators in the classical limit. Dissipators defined by double commutators arise naturally in dephasing dynamics, while those defined by double anticommutators are typically associated with noisy
Hamiltonians. The classical limit of such master equations is derived by reformulating the dissipative open dynamics in phase space using the Wigner-Weyl transform and Moyal bracket formalism, and by identifying the leading-order terms in a systematic $\hbar$-expansion. We first analyze a double-commutator master equation associated with energy
diffusion, and then turn to master equations containing a double anticommutator with the system
Hamiltonian, recently derived in the context of noisy non-Hermitian systems. For both classes of double-bracket equations, we establish a gradient-flow representation of the dynamics within both the
quantum and semiclassical formalisms. We further study the semiclassical
evolution generated by double-bracket master equations for the harmonic (integrable) and driven anharmonic (chaotic) oscillators, considering both classical and
quantum initial states. The dynamics are characterized through several observables, including mean position, momentum, and energy. The quantumness of the time-evolved state is assessed via the Wigner logarithmic negativity, and the interplay between double-bracket dissipation and chaotic dynamics is examined in detail. Finally, we extend our analysis to generalized master equations involving higher-order nested brackets, which arise naturally as a time-continuous formulation of spectral filtering techniques widely used in the numerical simulation of
quantum systems.
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Statistical Mechanics · Cross-listed from hep-th
Resource-Theoretic Quantifiers of Weak and Strong Symmetry Breaking: Strong Entanglement Asymmetry and Beyond
Yuya Kusuki, Sridip Pal and Hiroyasu Tajima
Quantifying how much a
quantum state breaks a
symmetry is essential for characterizing phases, nonequilibrium dynamics, and open-system behavior. For mixed states, however, conventional diagnostics of weak
symmetry breaking can miss a stronger form of
symmetry breaking associated with the possibility of exchanging conserved charges with an environment. We develop a resource theory of strong
symmetry breaking by identifying the appropriate free states and free operations, and, for channels on a fixed system, by showing that the latter are precisely the operations realizable without exchanging the conserved charge with the environment. We systematically construct measures of strong
symmetry breaking, including strong
entanglement asymmetry and covariance
matrices of
symmetry generators, for a broad class of
symmetry groups. We further completely characterize i.i.d. convertibility between arbitrary states under any compact Lie group strong
symmetry. This identifies the combinations of resource-theoretically valid measures that quantify strong
symmetry breaking for arbitrary states, including all mixed states. In particular, for $U(1)$
symmetry, if the states have positive variances of the conserved quantity and equal strong-
symmetry periods, the conversion rate is completely determined by the variance ratio whenever the input is pure or the output is weak symmetric. Thus, for these state conversions, the variance of the conserved quantity plays an operational role analogous to that of
entanglement entropy in
entanglement theory or
quantum Fisher information in the resource theory of weak asymmetry. We further show how weak
symmetry breaking is irreversibly converted into strong
symmetry breaking in open-system dynamics. We illustrate the framework with examples from
quantum field theory, strong-to-weak spontaneous
symmetry breaking, and a strong-
symmetry analogue of Mpemba-type dynamics.
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Materials Science · Cross-listed from cs.LG
A generative machine learning model for designing metal hydrides applied to hydrogen storage
Xiyuan Liu, Christian Hacker, Shengnian Wang et al. (+1 more)
Developing new metal hydrides is a critical step toward efficient hydrogen storage in carbon-neutral energy systems. However, existing materials databases, such as the Materials Project, contain a limited number of well-characterized hydrides, which constrains the discovery of optimal candidates. This work presents a framework that integrates causal discovery with a lightweight generative machine learning model to generate novel metal hydride candidates that may not exist in current databases. Using a
dataset of 450 samples (270 training, 90 validation, and 90 testing), the model generates 1,000 candidates. After ranking and filtering, six previously unreported chemical formulas and
crystal structures are identified, four of which are validated by density functional theory simulations and show strong potential for future experimental investigation. Overall, the proposed framework provides a scalable and time-efficient approach for expanding hydrogen storage
datasets and accelerating materials discovery.
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All authors Xiyuan Liu, Christian Hacker, Shengnian Wang, Yuhua Duan
Superconductivity
Field induced superconductivity in a magnetically doped two-dimensional crystal
Adrian Llanos, Veronica Show, Reiley Dorrian et al. (+1 more)
Magnetic field induced superconductivity is a rare property in nature due to the sensitivity of
spin-singlet Cooper pairing to time-reversal
symmetry breaking perturbations. However, in rare cases, an interplay between
magnetic fields and ions can be engineered to bring about superconductivity at finite fields. Here we use ultra-thin LaSb$_2$ doped with dilute Ce paramagnetic
impurities to demonstrate a
magnetic field-induced superconducting dome in a two-dimensional
crystal. The reduced dimensionality of the structure enables the use of an in-plane
magnetic field to dynamically suppress
spin fluctuations on the Ce-site, which leads to an anomalous enhancement of the critical temperature with increasing field. By modelling the
spin scattering dynamics across the experimental parameter space, we reveal insight into the complex nature of paramagnetic
impurities in
magnetic fields at low temperature, and how their manipulation can result in the ability to tune between competing
magnetic pair-breaking regimes. Realizing this physics in a two-dimensional crystalline setting invites the application of similar approaches to unconventional forms of superconductivity while also highlighting new experimental standards which should be employed when studying ultra-thin materials in general.
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All authors Adrian Llanos, Veronica Show, Reiley Dorrian, Joseph Falson