Strongly Correlated Electrons
Artificial versus Natural Atoms: The uncanny capability of the many-body Schrödinger equation to produce emergent behavior
Constantine Yannouleas
The paper reviews the theoretical and experimental progress achieved in the last 25 years in understanding the novel physics of artificial atoms and molecules as arising from the formation of Wigner molecules (WMs) of localized (to a stronger or lesser extent) fermionic or bosonic particles, which are finite
quantum analogs of the more familiar bulk Wigner
crystal. The term artificial atoms, as used here, encompasses a broad range of recently fabricated
quantum nanodevices and experimental apparatuses consisting of a finite number of mutually repelling confined particles, including two-dimensional
semiconductor and moiré transition metal dichalcogenide
quantum dots, as well as trapped ultracold neutral atoms or ions. These nano-sized or micro-sized artificial devices and apparatuses (in single well or multi-well of variable-shape arrangements) hold a great promise for technological applications in the field of
quantum information and
quantum computers, as well as for advances in fundamental many-body physics. Prominent
quantum effects of Wigner molecularization are the strong quenching of the spectral energy gaps, the appearance of rovibational spectra (in analogy with natural molecules),
entanglement, and pinning due to an external perturbation. In high
magnetic fields or at rapid rotation, WMs provide an alternative theory to the fractional
quantum Hall effect. The physics of Wigner molecules is shown to derive from the solutions of the many-body Schrödinger equation (MBSE) in the regime of strong interparticle correlations arising from the dominance of the potential over the kinetic energy, or from a high
magnetic field, as well as from a rapid rotation... (continues in the paper).
Read the full abstract ▾
Strongly Correlated Electrons
Quantum metric induced nonlinear transport in the hidden loop-current phase of kagome metal RbV$_3$Sb$_5$
Jia-Chen Shi, Shupeng Xu, Utkarsh Khandelwal et al. (+4 more)
A hidden low-temperature phase with possible loop-current order has been proposed in the kagome metals AV$_3$Sb$_5$ (A=K, Rb or Cs), but its experimental signatures remain subtle and indirect. Here, we use third-order nonlinear transport to probe this hidden phase in RbV$_3$Sb$_5$. At ~35 K, the longitudinal cubic response develops a strong kink and pronounced directional anisotropy with a strong departure from common relaxation time scaling, while the transverse cubic response acquires a
magnetic field-odd component at the same temperature. Their coincident onset identifies the third-harmonic response as a sensitive marker of the low-temperature electronic reconstruction with time-reversal broken
symmetry. Crucially, we find that the
quantum metric quadrupole contributes directly to the longitudinal third-order response. In a loop-current charge-density-wave model, its direction selective enhancement captures the observed angular reconstruction. Our work shows how higher-order nonlinear transport translates subtle changes in electronic
symmetry and
quantum metric into measurable electrical signatures in
quantum materials that is important for studying complex electronic phases of matter.
Read the full abstract ▾
All authors Jia-Chen Shi, Shupeng Xu, Utkarsh Khandelwal, Nashra Pistawala, Luminita Harnagea, Steven J. May, Ritesh Agarwal
Materials Science
Directional strain control of magnetism in MnBi$_2$Se$_4$, MnSb$_2$Se$_4$, and MnSb$_2$Te$_4$ freestanding monolayers
Swarnava Ghosh, Tanvir Sohail and Markus Eisenbach
MnBi$_2$Se$_4$, MnSb$_2$Se$_4$, and MnSb$_2$Te$4$ are layered
magnetic quantum materials of interest for spintronic and topological electronic applications, where control of
magnetic order at the atomic scale is essential. These materials are particularly sensitive to strain. We investigate their strain-dependent magnetism in the monolayer limit using first-principles calculations across the full two-dimensional strain space spanned by independent variations of the two in-plane strain components. Our results show that the Mn-projected local moments depend primarily on the volumetric strain, whereas the
magnetic ground state, exchange interactions, magnetocrystalline anisotropy, and ordering temperature show pronounced directional and composition-dependent responses. We also observe strain-induced competition between the phases, with MnBi$_2$Se$_4$, and MnSb$_2$Se$_4$ monolayers exhibiting a more diverse range of competing
magnetic states, while MnSb$_2$Te$_4$ monolayer remains ferromagnetic over a larger portion of strain space. MnSb$_2$Te$_4$ also exhibits a substantially larger out-of-plane magnetocrystalline anisotropy, while showing a weaker dependence on strain than the Se-based materials. The calculated
magnetic ordering temperature maps further highlight the role of two-dimensional strain to tune thermal
magnetic stability in these materials. These results establish magnetoelastic trends across this family of Mn-based chalcogenide monolayers.
Read the full abstract ▾
Soft Condensed Matter
Multistability by Design in Complex Triangular Mechanical Metamaterials
Chaviva Sirote-Katz and Yair Shokef
We introduce frustrated triangular networks that mix two different beam thicknesses. The two thicknesses separate the energetic costs of second-order buckling and angular deformation into four competing contributions. Using scaling arguments and mapping to an effective Ising description, we construct the system's phase diagram in terms of its dimensionless
geometric parameters. Selected beam arrangements exhibit local bistability: hexagonal motifs switch independently between opposite twisting states, while linear motifs support independently switchable beam states. In both cases, the number of mechanically stable configurations grows exponentially with system size. Experiments on fabricated silicone metamaterials confirm the predicted bistability and local switching. More generally, the allowed beam arrangements map onto rhombus tilings, producing a large combinatorial space of architectures. The system thus combines multiplicity in both architecture and stable deformation states, establishing beam-thickness patterning as a route for programming frustration, multistability, and extensive degeneracy in triangular mechanical metamaterials.
Read the full abstract ▾
Statistical Mechanics · Cross-listed from nlin.AO
Delay-induced multistability in one-dimensional swarmalators with common intrinsic frequency
Rommel Tchinda Djeudjo, Timoteo Carletti and Kevin P. O'Keeffe
We study the delayed one-dimensional swarmalator model when all units share a common intrinsic frequency {\omega}. Unlike the zero-frequency case, {\omega} cannot be removed by a rotating-frame transformation because delayed interactions retain the phase accumulated over the lag. The result is a two-order-parameter analogue of the delayed Kuramoto model: the asynchronous state acquires incoherence lobes, the synchronized state becomes a rotating branch stable even when both the spatial and phase couplings are repulsive, and the phase wave develops narrow resonant stability bands. These delay-selected windows overlap to produce broad branch coexistence, including a narrow window near K=-J where all three canonical states-asynchronous, phase wave, and synchronized-are simultaneously stable. In regions where no canonical branch is stable, the order parameters oscillate persistently.
Read the full abstract ▾
Materials Science
Fundamental concepts of thermal phonon coherence
Theodore Maranets, Haoran Cui, Milad Nasiri et al. (+2 more)
As scientists seek to transcend traditional material property relationships, novel structures with artificial periodicity, configurational complexity, and disorder are increasingly being explored. For
phonons, these architectures can induce significant phase correlations, which strongly shifts
lattice heat conduction away from the conventional framework of particle-like scattering. This thermal
phonon coherence can develop in space and time separately, resulting in distinct wave-like phenomena. Here we rigorously outline the theories of
phonon spatial and temporal coherence. Crucially, this review focuses on demystifying and building conceptual understanding of the fundamental principles linking the various thermal conductivity and
phonon property results reported in the literature. Furthermore, we use this understanding to establish a comprehensive physical picture of the wave nature of thermal
phonons, unifying the spatial and temporal coherence theories. Altogether, the theoretical dissections in this review provide an extensive knowledge base for understanding and engineering thermal
phonons in complex materials.
Read the full abstract ▾
All authors Theodore Maranets, Haoran Cui, Milad Nasiri, Evan Doe, Yan Wang
Mesoscale and Nanoscale Physics
Unveiling Three-Dimensional Skyrmion Transitions Through Vortices and Monopoles
Melissa E. Henderson, Daichi Kurebayashi, Benjamin Heacock et al. (+9 more)
Magnetic skyrmions represent
vortex-like
spin configurations that provide a robust platform for next-generation spintronic technologies. Although they are often treated as two-dimensional objects with integer topological charge, their extension into three-dimensional strings realizes other composite structures with unique device functionalities that transcend planar frameworks. Unfortunately, a lack of bulk probes has failed to realize such higher-dimensional topological structures and their implementations. Here, we report the first experimental visualization of three-dimensional topological $Q = 0$ skyrmion structures using
neutron scattering
tomography techniques across the
equilibrium phase of a Co$_8$Zn$_8$Mn$_4$ sample. Disordered skyrmion states reveal metastable skyrmioniums and composite topological objects novel to bulk systems.
Vortex-antivortex
lattices mediate changes in
topology, with unprecedented transition pathways via a coupling of merons and monopoles. The present realization of bulk Q = 0 quasiparticles and meron-mediated dynamics paves the way for higher-dimensional spintronic frameworks through multi-bit encoding architectures, unidirectional transport schemes, and monopole-mediated controls.
Read the full abstract ▾
All authors Melissa E. Henderson, Daichi Kurebayashi, Benjamin Heacock, Wangchun Chen, Charles W. Clark, David G. Cory, Dusan Sarenac, Shannon Watson, Jonathan S. White, Lisa DeBeer-Schmitt, Oleg A. Tretiakov, Dmitry A. Pushin
Statistical Mechanics
Derivation of Fokker-Planck equation and its entropy production
Tânia Tomé and Mário J. de Oliveira
We derive the Fokker-Planck equation and its
entropy production from the master equation. To this end we consider a discrete space of states where the master equation is defined and appropriate transition rates are introduced. A transition rate has two parts, one of which is the ordinary term proportional to the inverse of the spacing and the other is inversely proportional to the square of the spacing corresponding to the variance of the independent
stochastic variable. In the continuous space limit, we obtain the Fokker-Planck as well as the rate of
entropy production and the flux of
entropy. We also consider the case where the space of states is the phase space and discuss the equations appropriate for systems in contact with several heat reservoirs and for isolated systems.
Read the full abstract ▾
Strongly Correlated Electrons
Magnetic properties and Fermi-surface topology of kagome magnet HoV$_6$Sn$_6$
Tucker Beekmann, Ganesh Pokharel, Wyatt Edward Ackerman et al. (+3 more)
We report a study of the
magnetic properties and Fermi-surface
topology of the kagome magnet HoV$_6$Sn$_6$ using magnetization and tunnel-diode-oscillator (TDO) measurements. The temperature-dependent magnetization exhibits Curie-Weiss behavior at high temperatures and reveals long-range
magnetic order below $T_c$ $\approx$ 2.4 K. Below Tc, the field-dependent magnetization reveals pronounced
magnetic anisotropy, with saturation moments of $\approx$ 9.5 and 7 $\mu_B$ /Ho for fields applied along the out-of-plane and in-plane directions, respectively. To probe the Fermi surface, we perform TDO measurements in
magnetic fields up to 41.5 T and at temperatures down to 0.35 K. The TDO signal exhibits well-defined
quantum oscillations with multiple frequencies extending up to $\sim$ 9 kT. Angular- and temperature-dependent measurements are used to determine the Fermi-surface geometry and cyclotron effective masses, respectively. To elucidate the electronic structure, we perform first-principles calculations of the electronic bands, density of states (DOS), and Fermi surface. The calculated band structure exhibits flat-band features, van Hove singularities, and Dirac-like crossings near the Fermi level. The DOS near the Fermi level is dominated by the V-d orbitals, indicating that the V kagome layers play a major role in determining the low-energy electronic properties of HoV6Sn6. Our calculations further support a ferromagnetic ground state with the Ho moments oriented along the c axis, consistent with
neutron-scattering measurements. The calculated
quantum-oscillation frequencies from the Fermi-surface pockets of HoV6Sn6 are in overall good agreement with the experimentally observed frequencies. Our combined experimental and theoretical results provide insight into the
magnetic anisotropy and electronic structure of HoV$_6$Sn$_6$ and reveal its multiband Fermi-surface
topology.
Read the full abstract ▾
All authors Tucker Beekmann, Ganesh Pokharel, Wyatt Edward Ackerman, Stephen D. Wilson, David E. Graf, Keshav Shrestha
Mesoscale and Nanoscale Physics
Lumen Eek
Lowest-energy
excitons are usually expected to have nodeless $1s$-like envelope wavefunctions. We show that band
topology can obstruct this expectation. The
exciton envelope wavefunction is a section of the valence-conduction transition bundle, whose
topology can enforce momentum-space zeros, with their parity or signed total index fixed by the corresponding characteristic class. We exemplify this behavior in a minimal $PT$-symmetric three-band model with a rank-two transition bundle characterized by Euler number $\nu^e=2$. By directly solving the Bethe-Salpeter equation with both contact and Rytova-Keldysh interactions, we find that the lowest
exciton contains two zeros, each with index $+1$, and is less strongly bound than its topologically trivial counterpart. We further classify
topology-enforced
exciton nodal structures for real and complex transition bundles in dimensions $d \leq 3$. Our results establish the
topology of the transition bundle as a direct constraint on
exciton wavefunctions and spectra.
Read the full abstract ▾
Statistical Mechanics
Autonomous self-harmonic drift in Langevin dynamics causes a compaction of underlying domain for the density of Stochastic Localization
Ken Sekimoto
Our recent research on Langevin dynamics with self-harmonic drift and classical
spins has revealed a strong connection to “
Stochastic Localization," a concept attracting
attention in the fields of mathematical geometry and data science. Roughly speaking, the former can be viewed as a version of the latter in which the $n$-dimensional Euclidean space - the domain of the probability distribution function appearing in the latter - is “compactified” to the surface of an $n$-dimensional sphere. By comparing the two frameworks, we argue that this compactification is a consequence of requiring the drift to be autonomous. The relationship between the two approaches may expand the scope of
Stochastic Localization.
Read the full abstract ▾
Materials Science
Fracture of Lattice Materials from Low to High Relative Density
Adam P. Taylor, Sage Fulco and Kevin T. Turner
Lattice materials have highly tunable mechanical properties that are controlled by their internal geometry and base material behavior. While fracture models for low-density
lattices are well-established, the fracture of
lattices at relative densities above 30% remains largely unexplored. Here, we present an analytical model that combines homogenization methods and blunt-crack fracture theory to predict the fracture toughness of triangular and hexagonal
lattices over a wide range of relative densities. Finite element modeling corroborates the analytical framework and demonstrates a shift in failure mechanisms between low and high relative density regimes. At high relative densities, failure is dominated by nodal stress concentrations, which are strongly influenced by the local crack-tip geometry and the macroscopic crack path. Significant stress redistribution is observed as the relative orientation and
lattice fillet radius are varied, resulting in increased fracture toughness relative to baseline geometries. Furthermore, quasi-brittle poly(methyl methacrylate) (PMMA)
lattices achieve about a 1.6x enhancement in fracture toughness relative to perfectly brittle
lattices as failure is delayed by localized plasticity. Notably, some quasi-brittle
lattices are found to exceed the fracture toughness of their base material – a feature only possible when the
cell size is large compared to the base material's plastic radius. Experiments on
lattice fracture specimens made from
laser-cut PMMA validate the finite element results, but highlight the
stochastic nature of failure in brittle
lattice materials, especially at higher relative densities.
Read the full abstract ▾
Materials Science
Facet- and thickness-dependent band-edge alignment at ZrSe\texorpdfstring{$_3$}{3} surfaces: hybrid-functional calculations with spin-orbit coupling
Sandro G Holanda, Bruno Ipaves, Astrid Campos-Mata et al. (+4 more)
Transition-metal trichalcogenides MX$_3$ are quasi-one-dimensional van der Waals materials whose layers form through lateral chain binding, giving them an interlayer cleavage plane and in-plane electronic anisotropy. Among them, ZrSe$_3$ is stable under ambient conditions and semiconducting. Exfoliated
crystals expose four crystallographic planes, and electrocatalytic measurements on an individual
crystal assigned the hydrogen
evolution activity to the high-energy (210) facet rather than to the basal plane. Those non-basal surfaces remain uncharacterized, since the available calculations treat either the bulk
crystal or the free-standing basal monolayer. Here, we compute the surface energies and the
equilibrium morphology of these four surfaces with a dispersion-corrected semilocal functional, and their band-edge
alignment with the HSE06 hybrid functional including
spin-orbit coupling. The surface energies span nearly an order of magnitude, from \SI{0.097}{\joule\per\meter\squared} for (001) to \SI{0.869}{\joule\per\meter\squared} for (010), and the Wulff shape exposes the four observed planes with area fractions of \SI{17.1}{\percent}, \SI{4.4}{\percent}, \SI{71.4}{\percent}, and \SI{7.0}{\percent}. The ionization potential varies by \SI{0.45}{\electronvolt} between facets and the electron affinity by \SI{0.80}{\electronvolt}, the gap of (210) falls from 1.43 to \SI{0.94}{\electronvolt} between 10 and \SI{23}{\angstrom}, and (010) remains metallic. The facets separate according to whether the cut preserves or distorts the Se-Se dimer, and the distorted dimers concentrate the frontier states. Because the same dimer governs the bulk electronic structure of the MX$_3$ family, the criterion transfers to the related trichalcogenides.
Read the full abstract ▾
All authors Sandro G Holanda, Bruno Ipaves, Astrid Campos-Mata, Shreyasi Chattopadhyay, Pulickel M Ajayan, Douglas S Galvao, Marcelo L Pereira Junior
Strongly Correlated Electrons
Magnetic excitations of the strongly-anisotropic triangular XXZ model: a projected spin-product state approach
Achille Mauri and Frédéric Mila
Recent experiments have sparked interest on the ground-state properties and on the excitation spectrum of the
spin-$1/2$ triangular XXZ model with strong Ising-like anisotropy. In this work, we introduce and analyze a “projected” coherent-state approximation to the model, constructed by projecting
spin-product states onto the low-energy configurations of the triangular Ising antiferromagnet. Within this approximation, we discuss the structure of the ground-state ordering and the magnetization curve under a longitudinal field. We then discuss the excitation spectrum by linearizing equations of motion deriving from a time-dependent variational principle. This leads to a natural description of
spin-wave-like excitations within the strongly constrained
Hilbert space. At zero field, the variational approximation leads to a very flat landscape of quasi-degenerate states, which results in a low-energy pseudo-Goldstone mode in the excitation spectrum. We compare our results to experimental measurements on the cobaltite K$_{2}$Co(SeO$_{3}$)$_{2}$ (KCSO). Our approximation leads to a dramatic improvement as compared to linear
spin-wave theory. However, there remain deviations in the value of the pseudo-Goldstone gap and in the dispersion near $M$ points at low field.
Read the full abstract ▾
Materials Science
Altermagnetism produces pair emission and absorption from dark excitons and magnons in La$_2$O$_3$Mn$_2$Se$_2$
Birender Singh, Xian Xu, Sabrina R. Hatt et al. (+21 more)
Altermagnets' (AMs) non-relativistic
spin splitting enables novel states, spintronic and magneto-optical devices, though their optical signatures remain elusive. Here, we report
exciton-
magnon emission and absorption: optical sidebands from a
spin-forbidden dark
exciton, a direct consequence of altermagnetic
symmetry. Combined optical spectroscopy and first-principles calculations reveal that La$_2$O$_3$Mn$_2$Se$_2$ is an altermagnetic
insulator, hosting a strongly bound,
spin-forbidden dark
exciton and a higher-energy bright
exciton. Photoluminescence (PL) and absorption reveal mirror-image sidebands, Stokes-shifted in emission and anti-Stokes-shifted in absorption, symmetric about the dark
exciton, whose energy shifts and spectral shapes match the
magnon energy scale and density of states measured independently by inelastic
neutron scattering. The PL intensity tracks the full equal-time
spin-
spin correlator, combining static and dynamical contributions, and rules out alternative processes. This directly couples PL to magnetism, with potential for magneto-optical devices. These results establish
exciton-
magnon spectroscopy as a new route for optically identifying and exploiting AMs.
Read the full abstract ▾
All authors Birender Singh, Xian Xu, Sabrina R. Hatt, Suvodeep Paul, Yu-Mi Wu, Chao-Chun Wei, Violet Williams, Kyung-Mo Kim, Yihao Zhang, Mohamed Shehabeldin, Cameron Grant, April Li, Michael Geiwitz, Xiaoyin Li, Garrett E. Granroth, Feng Liu, Qiong Ma, Benedetta Flebus, Judy J. Cha, Vinod M. Menon, Benjamin A. Frandsen, Diana Y. Qiu, Huiwen Ji, Kenneth S. Burch
Materials Science
Far-field terahertz spectroscopy across the charge-density-wave transition in 2H-NbSe$_2$
Dmitriy Yavorskiy, Adil Rehman, Wojciech Brzezicki et al. (+7 more)
Charge-density-wave (CDW) formation in 2H-NbSe$_2$ modifies the low-energy electronic structure and gives rise to collective excitations coupled to the
lattice. Here, we investigate bulk 2H-NbSe$_2$ single
crystals using far-field terahertz time-domain spectroscopy (THz-TDS) in reflection geometry across the CDW transition at $T_{\mathrm{CDW}} \approx 33$~K. Below $T_{\mathrm{CDW}}$, the THz response shows a pronounced high-frequency feature near 1.5~THz together with longer-lived sub-THz oscillations. Both responses progressively weaken upon warming and are strongly suppressed across the CDW transition, supporting their association with the CDW state. Using time-dependent Ginzburg–Landau simulations, we reproduce the main features of the experimental THz response, associating the high-frequency response mainly with CDW amplitude dynamics and the sub-THz response with defect-pinned phase dynamics. The $\sim1.5$~THz feature lies close to the frequency range reported for the Raman CDW amplitude mode, while coupling to
lattice degrees of freedom may also influence its spectral position. We also performed complementary angle-resolved photoemission spectroscopy measurements, which reveal momentum-selective redistribution of near-Fermi-level spectral weight across the transition. Together, these results show that far-field THz spectroscopy provides a sensitive probe of collective CDW dynamics in bulk 2H-NbSe$_2$.
Read the full abstract ▾
All authors Dmitriy Yavorskiy, Adil Rehman, Wojciech Brzezicki, Jan Skolimowski, Marcin Białek, Wojciech Knap, Dawid Wutke, Natalia Olszowska, Andrzej Wiśniewski, Ashutosh S. Wadge
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Donghoon Kim and Tomotaka Kuwahara
Understanding what limits many-body
quantum entanglement is a central problem in physics. Spatial locality has long provided a fundamental mechanism: correlations between a region and its complement must be mediated through a small spatial interface, thereby constraining their
entanglement. Here we show that universal constraints on
entanglement can persist even when interactions are strongly nonlocal, through collectivity: many weak interactions generate fluctuations controlled by their square-summed, rather than total, strength. We establish this mechanism rigorously for generic gapped
Hamiltonians with Kac-normalized power-law interactions $r^{-\alpha}$ on a $D$-dimensional
lattice. For arbitrary bipartitions, we prove that the ground-state
entanglement scales at most logarithmically with system size for $\alpha<D/2$ and subextensively for $D/2<\alpha<D$, due to suppressed collective fluctuations around individual sites. For spatially regular bipartitions with codimension-one boundaries, we use a renormalization-group construction to extend this suppression to larger length scales, yielding polylogarithmic scaling for $D/2 < \alpha < (D+1) / 2$ and parametrically stronger subvolume bounds for $(D+1)/2<\alpha<D$. We also establish the corresponding optimality results: for arbitrary bipartitions, the logarithmic scaling for $\alpha<D/2$ is optimal and $\alpha=D/2$ marks the optimal threshold for universal logarithmic bounds, while for regular bipartitions the threshold at $\alpha=(D+1)/2$ is likewise optimal for universal polylogarithmic bounds when $D\ge2$. Together, these results reveal collectivity as a fundamental mechanism for constraining many-body
entanglement alongside spatial locality.
Read the full abstract ▾
Materials Science
Accelerating phase-field simulations on exascale computing systems for faster-than-real-time precipitate aging predictions
Stephen DeWitt, David J. Gardner, Philip Fackler et al. (+4 more)
Three-dimensional phase-field simulations are a gold-standard for microstructure prediction for materials, but their computational cost often limits application-relevant calculations to modest domain sizes and timescales. Here, we present a holistic approach for accelerating
Fourier pseudospectral phase-field simulations by combining performance-portable GPU computing, large-scale distributed-
memory parallelism, and high-order implicit-explicit time integration within the MEUMAPPS C++ framework. We demonstrate this approach with a 1.5-billion-grid-point simulation of the growth and coarsening of 1,920 gamma” precipitates in a Ni-Nb-Fe
alloy. The simulated seven-hour heat treatment is completed in 5.5 hours, making the calculation faster than real time and an estimated 217-501x faster than a CPU-only, first-order baseline. This performance makes three-dimensional simulations of thousands of interacting precipitates tractable, enabling quantitative studies ocollective microstructural phenomena, large simulation ensembles, and real-time integration into controlling and interpreting experiments. Benchmarking shows single-node GPU speedups of up to 17.5x relative to comparable CPU resources, near-ideal strong scaling to 4096 GPUs for a 12-billion-grid-point problem, and a further 2.6-2.9x acceleration from fourth-order time integration at scientifically relevant error tolerances. These results establish a performance-portable strategy for exploiting leadership-scale GPU systems that is applicable to a broad class of
Fourier pseudospectral simulations beyond phase-field models such as fluid dynamics and
crystal plasticity simulations.
Read the full abstract ▾
All authors Stephen DeWitt, David J. Gardner, Philip Fackler, Yonggil Song, Miroslav Stoyanov, Carol S. Woodward, Balasubramaniam Radhakrishnan
Materials Science
Measuring trainable degrees of freedom in materials graph neural networks: a random-subspace intrinsic dimension analysis
Shehroz Ahmad Shoaib and Kangming Li
Final predictive accuracy is the standard basis for comparing graph neural networks (GNNs) in materials-property prediction, but it does not show how strongly performance depends on access to trainable parameter-space directions. Here, we introduce trainable-degree dependence as a complementary characterization of materials GNN learning. Using random-subspace intrinsic-dimension analysis, we train CGCNN, ALIGNN, and DimeNet++ in randomly oriented parameter subspaces across six prediction tasks and measure how performance recovers as independent trainable degrees of freedom are restored. The resulting recovery curves separate endpoint accuracy from the trainable-dimensional demand required to recover it. They reveal distinctions that final errors alone miss: metallic classification and log-bulk-modulus regression recover near-reference performance from small fractional subspaces, formation-energy and band-gap prediction show stronger architecture dependence, and
phonon prediction is most sensitive to dimensional restriction.
Dataset-size sweeps show that band-gap models require larger fractional subspaces as training data grows, whereas formation-energy and bulk-modulus responses are more stable. A width sweep shows that fractional thresholds can remain stable while absolute threshold dimensions increase with model size. Random-subspace analysis therefore provides a targeted stress test for how materials GNNs use their optimization space.
Read the full abstract ▾
Strongly Correlated Electrons
Excitonic Stripe Order in the Two-Orbital Hubbard-Kanamori Model
Rafael D. Soares, Luke Staszewski, Chunhan Feng et al. (+1 more)
Excitonic condensation and stripe formation are two distinct manifestations of electronic correlations. While excitonic order naturally arises in multi-orbital systems, stripe order is a prominent feature of doped correlated-electron models. Here, we investigate an excitonic analogue of stripe order in the two–orbital Hubbard-Kanamori model on the square
lattice, characterized by a spatial modulation of inter-orbital particle-hole coherence and, in the orbital-parity-symmetric limit, spontaneous breaking of a relative orbital $\mathbb{Z}_2$
symmetry. Using unrestricted real-space Hartree-Fock calculations complemented by random-phase-approximation instability analysis, we determine how the Kanamori interactions select different excitonic channels. The sign of Hund's exchange controls the
spin character of the condensate: ferromagnetic Hund coupling favors triplet excitonic order, whereas antiferromagnetic Hund coupling stabilizes singlet excitonic order. Upon doping, commensurate excitonic density waves develop incommensurate textures, including excitonic stripes and, in the triplet sector, spiral excitonic density waves. We further show that
crystal-field splitting strongly reorganizes the excitonic instability by modifying inter-orbital nesting and can stabilize triplet excitonic order even in the absence of pair hopping. Our results establish excitonic stripes as a distinct
symmetry-broken state of multi-orbital correlated systems and identify microscopic routes for their stabilization.
Read the full abstract ▾
All authors Rafael D. Soares, Luke Staszewski, Chunhan Feng, Alexander Wietek
Materials Science
Linking Topological Medium Range Order and Density-Wave Coherence to Metallic Glass Ductility
Minhazul Islam, Muchen Wang, Andrea Fantin et al. (+10 more)
Metallic glasses exhibit pronounced composition-dependent mechanical properties, yet identifying the structural origins of these changes remains difficult. An outstanding issue is how to correlate different forms of medium range order (MRO), defined at different length scales and accessed through different experimental observables, and to understand their connection to properties. We combine synchrotron reduced density function, G(r), with machine-learning-assisted four dimensional scanning transmission electron microscopy (4D-STEM) to examine
geometric and topological MRO in five Zr-based metallic glasses. Density wave analysis of G(r) provides a
geometric MRO descriptor through the coherence length of atomic density correlations, while 4D-STEM reveals nanoscale topological and chemical MRO motifs, including
crystal-like local ordering with distinct rotational
symmetries. We show that the G(r)-derived coherence length captures an important baseline tendency for cooperative ductile relaxation, while composition-dependent topological MRO provides an additional structural contribution that helps explain the observed mechanical responses. In particular, increasing Zr content suppresses Cu-rich FCC-like MRO, increases the cooperative coherence volume, and promotes fine Zr-rich HCP-like local order associated with enhanced ductility. These results identify the combined structural influence of
geometric and topological MRO as a key basis for composition-dependent mechanical response in metallic glasses.
Read the full abstract ▾
All authors Minhazul Islam, Muchen Wang, Andrea Fantin, Geun Hee Yoo, Ji Young Kim, Hamdan Ashfaq, Eun Soo Park, Robert Maass, Yunzhi Wang, Yue Fan, Hee-Suk Chung, Sang-Chul Lee, Jinwoo Hwang
Mesoscale and Nanoscale Physics
Magnetoplasmon molecule
A. V. Larionov, A. V. Gorbunov, A. B. Van'kov et al. (+3 more)
We investigate a two-dimensional electron system in an external
magnetic field. An intrinsic four-particle excitation of the electron system, which we term a magnetoplasmon molecule, is observed. The molecule comprises two identical electrons and two Fermi holes with opposite
spins. Both electrons and one Fermi hole participate in the collective
plasma oscillations of the electron system, whereas the second Fermi hole neutralizes the excess electronic charge. We examine the interaction between the magnetoplasmon molecule and a magnetoexciton condensate.
Read the full abstract ▾
All authors A. V. Larionov, A. V. Gorbunov, A. B. Van'kov, D. A. Shchigarev, L. V. Kulik, V. Umansky
Statistical Mechanics · Cross-listed from quant-ph
Out-of-Time-Ordered Correlators Beyond Lindblad
Elisa Vallini, Felix Fritzsch and Pieter W. Claeys
Out-of-time-ordered correlators (OTOCs) provide a powerful probe of
quantum chaos and scrambling. While the Lindblad formalism is often used to describe OTOCs in open systems, microscopic mechanisms that give rise to the Lindblad equation at the level of time-ordered correlation functions do not necessarily justify this approach at the level of OTOCs. Starting from a microscopic model of a subsystem coupled to a random bath, we show that the resulting OTOC dynamics contains an additional contribution compared to the standard Lindblad approach. This contribution, induced by correlations between different replicas, allows key properties of the underlying
unitary dynamics such as long-time freeness to be retained and information scrambling to be captured more faithfully. As an application, we show that this extended formalism can be used to numerically study OTOCs in large closed systems by replacing part of the system with a dissipative boundary, offering a way to study operator spreading and higher-order correlations beyond directly accessible system sizes.
Read the full abstract ▾
Strongly Correlated Electrons
Spectroscopy of phonon-coupled integer and fractional Chern insulators: emergence of polarons and chirality deficit of graviton mode
Min Long, Yuzhu Wang and Zi Yang Meng
Strong electron-
phonon coupling can destabilize both Chern
insulators (CIs) and fractional Chern
insulators (FCIs) in favor of charge order, but whether the instabilities in CI and FCI share a common microscopic mechanism remains unclear. In this paper, we address this question by studying a flat-band Haldane model coupled to dynamical Holstein
phonons at integer and fractional fillings using density-
matrix renormalization group with local basis optimization. We find that the low-energy effects of
phonons are dominated by their dressing of charge-neutral collective modes. In the CI and FCI,
phonons dress
excitons and magnetorotons into composite modes that we identify as
exciton polarons and magnetoroton polarons, respectively. These modes soften strongly upon approaching the transition, while the momenta of their energy minima anticipate the ordering wave vectors of the charge-ordered phases. The
phonon spectrum, in turn, acquires dispersive features inherited from the
exciton and magnetoroton modes, providing direct
lattice signatures of these neutral excitations. Within the FCI phase, electron-
phonon coupling also enhances the opposite-chirality spectral weight of the graviton response, thereby resulting in a chirality deficit. Our results provide a unified excitation-based picture of
phonon-driven instabilities in CIs and FCIs and establish
lattice dynamics as a probe of their neutral collective modes.
Read the full abstract ▾
Disordered Systems and Neural Networks · Cross-listed from math-ph
Coherent energy cascades in nonlinear disordered Hamiltonians
Anxo Biasi, Brad Cownden, Oleg Evnin et al. (+1 more)
The familiar wave kinetic theory revolves around turbulent energy cascades characterized by random phases of the individual normal modes. By contrast, recent years have revealed turbulent cascades where the transfer of energy is mediated by phase-coherent dynamics. Such coherent cascades have been previously established in deterministic systems with a tightly controlled algebraic structure of the mode interactions, such as nonlinear Schrödinger equations. Here, we show that the presence of phase-coherent cascades is robust with respect to substantial alterations of the mode couplings. We prove that, in infinite-dimensional resonant
Hamiltonian systems with fully resonant normal mode spectra and random nonlinear couplings, a structured subset of couplings — an infinitesimal fraction of the total — suffices to support coherent cascades characterized by phase
alignment, the formation of power-law spectra, and either unbounded growth of Sobolev norms or a finite-time blow-up. Numerical simulations further demonstrate the emergence of coherent cascades from random initial data through a process of phase locking, suggesting a mechanism for their emergence in broader classes of initial data and systems. We thus show that disordered mode interactions can sustain, rather than block, coherent energy transport across arbitrarily distant scales.
Read the full abstract ▾
All authors Anxo Biasi, Brad Cownden, Oleg Evnin, Alvaro Iturbe Jabaloyes
Statistical Mechanics · Cross-listed from quant-ph
Entanglement spectrum and magic in higher-dimensional free fermionic systems
Beatrice Magni, Daniele Iannotti and Riccardo Travaglino
We study fermionic non-local magic in higher-dimensional free-
fermion systems through the lens of the
entanglement spectrum. For translationally invariant Gaussian states in strip geometries, dimensional reduction maps the problem to independent lower-dimensional momentum sectors, leading in two dimensions to a multiplicative logarithmic violation of the boundary law analogous to Gioev-Klich-Widom scaling. We further show that the second Rényi fermionic non-local magic is bounded by the capacity of
entanglement and introduce an
entanglement-temperature deformation that probes the low-energy structure of the
entanglement Hamiltonian. Applied to the matter-Majorana sector of the Kitaev model, this response is exponentially suppressed in the Abelian phase and algebraic in the non-Abelian phase, where its ratio with the capacity approaches a universal constant. Out of
equilibrium, we extend the quasi-particle description to fermionic non-local magic in higher-dimensional quenches and show that random Gaussian
circuits exhibit diffusive spreading in two spatial dimensions.
Read the full abstract ▾
Quantum Gases · Cross-listed from quant-ph
Fast Hamiltonian engineering from cut polytope geometry
Thomas Joachim Friese, Özgün Kum, Aram W. Harrow et al. (+1 more)
Hamiltonian engineering (HE) simulates
quantum dynamics under a target
Hamiltonian using a native entangling system
Hamiltonian and restricted control, with applications from
quantum gate design to analog
quantum simulation. Observing that, for many systems, formulating HE as a linear program only requires specific commutation relations between the control pulses and the system
Hamiltonian, we provide a unified framework for broad classes of $2$-local
qubit, qudit, and fermionic systems. We reformulate time-optimal HE as a complex $k$-cut polytope problem, with $k$ the number of distinct phases in these commutation relations, and prove it NP-complete for every finite $k$. We therefore relax the polytope to the elliptope and apply a Krivine-type rounding, yielding pulses informed by the system and target
Hamiltonians, which we then use in a linear program. We derive how many informed pulses are necessary and sufficient for the linear program to be reliably feasible. Additionally mixing in uniformly sampled pulses guarantees a solution close to the relaxation value from $\mathrm{O}(m)$ pulses, with $m$ the number of interaction terms. Together with upper and lower bounds on the optimal
quantum run time, this yields an $\mathrm{O}(\sqrt{m})$ approximation ratio. In
benchmarks on a fully connected Ising model, a chiral clock model for qudits, and the fermionic Harper-Hofstadter model, our approach attains near-optimal
quantum run times wherever the optimum is computable, reaches run times that saturate with the
lattice size in the fermionic case, and outperforms state-of-the-art methods with $\mathrm{O}(m)$ pulses. This establishes a unified approach with provable guarantees to the automatic programming of analog
quantum simulators.
Read the full abstract ▾
All authors Thomas Joachim Friese, Özgün Kum, Aram W. Harrow, Martin Kliesch
Strongly Correlated Electrons · Cross-listed from quant-ph
Digital Quantum Algorithms for Generating and Utilizing Spin Squeezed States
Mingru Yang, Ruby Wei and Chao Yin
Spin squeezed states (SSSs) are conventionally viewed as analog resources for
quantum metrology. Here we develop
algorithms to efficiently generate and exploit SSSs on a digital
quantum computer. We introduce an adaptive local-
circuit protocol that prepares SSSs with squeezing parameter $\xi$ in depth $\mathrm{O}\left(\log{1/\xi}\right)$, yielding an exponential improvement over non-adaptive approaches. We prove that this depth is optimal for permutation symmetric SSSs by deriving a matching lower bound on
entanglement entropy. We further leverage the squeezing paradigm to deterministically prepare the Dicke states using asymptotically fewer resources than prior methods. Remarkably, classical simulations of our preparation protocols under realistic noise models predicts a metrological gain of 4.2 dB beyond the standard
quantum limit with 55 superconducting
qubits in total including ancillae. Our work paves the way for performing
quantum metrology on near-term digital
quantum devices.
Read the full abstract ▾
Statistical Mechanics
Nonreciprocal Chiral Automata
Andrew A. Allocca, Armin Rahmani, Pouyan Ghaemi et al. (+1 more)
Odd pressure is a parity-odd transport coefficient that gives an isotropic pressure response to vorticity in compressible two-dimensional fluids. By asymmetrically coupling vortical and compressional modes, it provides a direct mechanism for a nonreciprocal hydrodynamic response reminiscent of several biological systems. Yet microscopic models realizing odd pressure as a transport coefficient are relatively scarce. Here, we construct one such model using a
lattice-gas cellular automaton based on the Frisch-Hasslacher-Pomeau II model with rest particles and chiral collisions, whose Chapman-Enskog coarse-graining produces a nonzero odd pressure coefficient. The key ingredient is a local parity-breaking collision that weakly rotates moving particles in the presence of a rest particle. At hydrodynamic scales, this microscopic rule acts as an effective
magnetic field, converting the model's bulk viscosity into odd pressure. More generally, we derive expressions relating Hall viscosity, odd pressure, and odd torque to their parity-even counterparts in our model.
Read the full abstract ▾
All authors Andrew A. Allocca, Armin Rahmani, Pouyan Ghaemi, Sriram Ganeshan
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Characterizing quantum precision enhancement for multiple currents in open quantum systems
Khalak Mahadeviya, Sheikh Parvez Mandal, Mahasweta Pandit et al. (+3 more)
The kinetic uncertainty relation (KUR) constrains fluctuations of individual currents in classical nonequilibrium systems in terms of the dynamical activity, which quantifies the average number of transitions per unit of time. Here, we derive a multi-current KUR (MKUR) establishing the precision limit for multiple currents generated in classical
stochastic processes in the nonequilibrium steady state. We then apply our theory to identify
quantum devices whose correlated current fluctuations surpass this classical limit by comparing the
quantum system to a classical emulator with the same average currents in the steady state. In this way, violations of the emulator's MKUR have a clear physical meaning, i.e., that the
quantum-coherent
evolution reduces joint current fluctuations below what is possible for a classical Markovian system with the same energy-level structure and incoherent resources. Since the MKUR incorporates correlations between currents, its violation pinpoints nonclassical fluctuations in parameter regimes where the single-current KUR is satisfied. We illustrate the essential and complementary role of these bounds for characterizing joint current precision with two examples: a coherently driven two-level system and an experimentally motivated model of a three-level heat engine subject to parasitic environmental couplings.
Read the full abstract ▾
All authors Khalak Mahadeviya, Sheikh Parvez Mandal, Mahasweta Pandit, Javier Prior, Mark T. Mitchison, Saulo V. Moreira