arXiv subjects

Andrew A. Allocca

Publications and source records attributed to Andrew A. Allocca.

17 recordsLinked to original sources

arXiv2026

Odd fluids from chiral cellular automata

Cellular automata are discrete dynamical systems defined on a lattice, in which each site carries a finite set of states that evolve in time according to local deterministic rules. An important application of cellular automata is in lattice gas models of fluids, where the cellular automaton framework provides a particle-based microscopic description of hydrodynamic behavior. The macroscopic fluid equations emerge after coarse-graining over many lattice sites and time steps, offering a bottom-up route to hydrodynamics. A celebrated example is the Frisch-Hasslacher-Pomeau (FHP) model, an automaton defined on a two-dimensional triangular lattice that yields the two-dimensional Navier-Stokes equations upon coarse-graining. In this work, we construct a parity-breaking generalization of the FHP model through two modifications: introducing chiral two-body collision rules and systematically rotating particle velocities to mimic the effect of a background magnetic field. We show that this automaton yields a hydrodynamic model with odd viscosity, a transverse transport coefficient that is a hallmark of odd fluids. We verify the analytical transport coefficients using Poiseuille-flow simulations of the chiral FHP automaton. Our results demonstrate that the chiral automaton introduced here provides a bridge between microscopic parity-breaking scattering processes and macroscopic odd-fluid hydrodynamics.

cond-mat.stat-mech↗

arXiv2026

Universality of stochastic control of quantum chaos with measurement and feedback

We investigate universal features of measurement-and-feedback control of quantum chaotic dynamics by examining the quantum Arnold cat map, a paradigmatic model of quantum chaos. Inspired by probabilistic control of classical chaos, our protocol stochastically alternates between intrinsic instability and engineered control operations that steer trajectories toward a target point. Simulation of exact quantum dynamics and a semiclassical truncated Wigner approximation reveal universal properties of the cat map's control transition. To further characterize this universality, we introduce the inverted harmonic oscillator as an analytically tractable effective model of instability. By integrating numerical simulations, a semiclassical Fokker-Planck description, and a direct spectral analysis of the stochastic quantum channel, we identify quantum signatures absent in classical limits. The close agreement between quantum simulation, truncated Wigner approximation, and inverted oscillator analysis shows that universal features of the transition are set by uncertainty-limited quantum fluctuations and are insensitive to genuine quantum interference.

quant-ph↗

arXiv2025

Measuring the Hall Viscosity of the Laughlin State on Noisy Quantum Computers

Hall viscosity is a quantized nondissipative stress response of a fractional quantum Hall (FQH) fluid to adiabatic geometric deformations. Despite strong theoretical interest, its experimental observation in the FQH state has remained elusive, making it a promising target for realization on current NISQ devices. In this work, we employ a quasi-one-dimensional model of an FQH state coupled to a background metric to probe the geometric response under a metric quench. We design and implement a quantum-circuit protocol that realizes a Hilbert-space-truncated version of the model and extracts the Hall viscosity from the geometric response encoded in the wavefunction dynamics of the device. While the truncation prevents us from accessing the fully quantized value of Hall viscosity, the hardware data nevertheless show excellent agreement with analytical and numerical predictions within this restricted regime.

cond-mat.str-el↗

arXiv2024

Strange metal in the doped Hubbard model via percolation

Many strongly correlated systems exhibit strange metallic behavior in certain parameter regimes characterized by anomalous transport properties that are irreconcilable with a Fermi-liquid-like description in terms of quasiparticles. The Hubbard model is a standard theoretical starting point to examine the properties of such systems and also exhibits non-Fermi-liquid behavior in simulations. Here we analytically study the two-dimensional hole-doped Hubbard model in the large $U$ limit, first identifying a doping-induced percolation transition in the low-energy sector occurring at a definite critical doping $p_c$ depending on lattice structure. Using the critical properties near this transition we rewrite the Hubbard Hamiltonian and motivate a low-energy lattice-independent large-$N$ model with distinct non-Fermi-liquid properties. We show that this model has linear-in-$T$ resistivity with doping-dependent slope maximized at $p=p_c$ and power-law optical conductivity $\sim |ω|^{-2/3}$. Though the parameters used in developing this theory mean it cannot be directly applied to the cuprate superconductors, we nevertheless reproduce several important phenomena observed in their strange metal phase, and also predict these same qualitative behaviors to manifest in other lattices near concrete hole dopings.

cond-mat.str-el↗

arXiv2024

Statistical Mechanics of Stochastic Quantum Control: $d$-adic Rényi Circuits

The dynamics of quantum information in many-body systems with large onsite Hilbert space dimension admits an enlightening description in terms of effective statistical mechanics models. Motivated by this fact, we reveal a connection between three separate models: the classically chaotic $d$-adic Rényi map with stochastic control, a quantum analog of this map for qudits, and a Potts model on a random graph. The classical model and its quantum analog share a transition between chaotic and controlled phases, driven by a randomly applied control map that attempts to order the system. In the quantum model, the control map necessitates measurements that concurrently drive a phase transition in the entanglement content of the late-time steady state. To explore the interplay of the control and entanglement transitions, we derive an effective Potts model from the quantum model and use it to probe information-theoretic quantities that witness both transitions. The entanglement transition is found to be in the bond-percolation universality class, consistent with other measurement-induced phase transitions, while the control transition is governed by a classical random walk. These two phase transitions merge as a function of model parameters, consistent with behavior observed in previous small-size numerical studies of the quantum model.

quant-ph↗

arXiv2023

Separate measurement- and feedback-driven entanglement transitions in the stochastic control of chaos

We study measurement-induced entanglement and control phase transitions in a quantum analog of the Bernoulli map subjected to a classically-inspired control protocol. When entangling gates are restricted to the Clifford group, separate entanglement ($p_\mathrm{ent}$) and control ($p_\mathrm{ctrl}$) transitions emerge, revealing two distinct universality classes. The control transition has critical exponents $ν$ and $z$ consistent with the classical map (a random walk) while the entanglement transition is revealed to have similar exponents as the measurement-induced phase transition in Clifford hybrid dynamics. This is distinct from the case of generic entangling gates in the same model, where $p_\mathrm{ent} = p_\mathrm{ctrl}$ and universality is controlled by the random walk.

cond-mat.dis-nn↗

arXiv2023

Fluctuation-dominated quantum oscillations in excitonic insulators

The realization of excitonic insulators in transition metal dichalcogenide systems has opened the door to explorations of the exotic properties such a state exhibits. We study theoretically the potential for excitonic insulators to show an anomalous form of quantum oscillations: the de Haas-van Alphen effect in an insulating system. We focus on the role of the interactions that generate the energy gap and show that it is crucial to consider quantum fluctuations that go beyond the mean field treatment. Remarkably, quantum fluctuations can be dominant, and lead to quantum oscillations than are significantly larger than those predicted using mean field theory. Indeed, in experimentally accessible parameter regimes these fluctuation-generated quantum oscillations can even be larger than what would be found for the corresponding gapless system.

cond-mat.mes-hall↗

arXiv2022

Quantum oscillations in interaction-driven insulators

In recent years it has become understood that quantum oscillations of the magnetization as a function of magnetic field, long recognized as phenomena intrinsic to metals, can also manifest in insulating systems. Theory has shown that in certain simple band insulators, quantum oscillations can appear with a frequency set by the area traced by the minimum gap in momentum space, and are suppressed for weak fields by an intrinsic "Dingle damping" factor reflecting the size of the bandgap. Here we examine quantum oscillations of the magnetization in excitonic and Kondo insulators, for which interactions play a crucial role. In models of these systems, self-consistent parameters themselves oscillate with changing magnetic field, generating additional contributions to quantum oscillations. In the low-temperature, weak-field regime, we find that the lowest harmonic of quantum oscillations of the magnetization are unaffected, so that the zero-field bandgap can still be extracted by measuring the Dingle damping factor of this harmonic. However, these contributions dominate quantum oscillations at all higher harmonics, thereby providing a route to measure this interaction effect.

cond-mat.str-el↗

arXiv2021

Low-frequency Quantum Oscillations from Interactions in Layered Metals

Metals composed of weakly-coupled, stacked layers possess a Fermi surface that slightly varies in size along the stacking direction. This appears in de Haas-van Alphen (dHvA) oscillations of the magnetisation with magnetic field as two close frequencies, corresponding to the two extremal Fermi surface cross-sectional areas. We show that, for layered materials of sufficiently high mobility, Coulomb interactions can have a dramatic effect on the form of the dHvA oscillations: there is also generically an oscillation at the small difference of the two large frequencies. We determine the size and form of this effect, and show that it probes the short-range part of the Coulomb interactions within the layered material. We argue that this interaction effect may explain recent experimental observations of anomalous low-frequency dHvA oscillations in the ultrapure delafossites.

cond-mat.mes-hall↗

arXiv2019

Manifestations of spin-orbit coupling in a cuprate superconductor

Exciting new work on Bi2212 shows the presence of non-trivial spin-orbit coupling effects as seen in spin resolved ARPES data [Gotlieb et al., Science, 362, 1271-1275 (2018)]. Motivated by these observations we consider how the picture of spin-orbit coupling through local inversion symmetry breaking might be observed in cuprate superconductors. Furthermore, we examine two spin-orbit driven effects, the spin-Hall effect and the Edelstein effect, focusing on the details of their realizations within both the normal and superconducting states.

cond-mat.supr-con↗

arXiv2019

Cavity Higgs-Polaritons

Motivated by the dramatic success of realizing cavity exciton-polariton condensation in experiment we consider the formation of polaritons from cavity photons and the amplitude or Higgs mode of a superconductor. Enabled by the recently predicted and observed supercurrent-induced linear coupling between these excitations and light, we find that hybridization between Higgs excitations in a disordered quasi-2D superconductor and resonant cavity photons can occur, forming Higgs-polariton states. This provides the potential for a new means to manipulate the superconducting state as well as potential for novel photonic cavity circuit elements.

cond-mat.supr-con↗

arXiv2019

Cavity Quantum Eliashberg Enhancement of Superconductivity

Driving a conventional superconductor with an appropriately tuned classical electromagnetic field can lead to an enhancement of superconductivity via a redistribution of the quasiparticles into a more favorable non-equilibrium distribution -- a phenomenon known as the Eliashberg effect. Here we theoretically consider coupling a two-dimensional superconducting film to the quantized electromagnetic modes of a microwave resonator cavity. As in the classical Eliashberg case, we use a kinetic equation to study the effect of the fluctuating, dynamical electromagnetic field on the Bogoliubov quasiparticles. We find that when the photon and quasiparticle systems are out of thermal equilibrium, a redistribution of quasiparticles into a more favorable non-equilibrium steady-state occurs, thereby enhancing superconductivity in the sample. We predict that by tailoring the cavity environment (e.g. the photon occupation and spectral functions), enhancement can be observed in a variety of parameter regimes, offering a large degree of tunability.

cond-mat.supr-con↗

arXiv2018

Cavity superconductor-polaritons

Following the recent success of realizing exciton-polariton condensates in cavities, we examine the hybridization of cavity photons with the closest analog of excitons within a superconductor, states called Bardasis-Schrieffer (BS) modes. Though BS modes do not typically couple directly to light, one can engineer a coupling with an externally imposed supercurrent, leading to the formation of hybridized Bardasis-Schrieffer-polariton states, which we obtain both via direct solution and through the derivation of an effective Hamiltonian picture for the model. These new excitations have nontrivial overlap with both the original photon states and $d$-wave superconducting fluctuations, implying that their condensation could produce a finite $d$-wave component of the superconducting order parameter--an $s\pm id$ superconducting state.

cond-mat.mes-hall↗

arXiv2018

Fingerprints of Berry phases in the bulk exciton spectrum of a topological insulator

We examine excitons formed in the bulk of a topological insulator as the system is tuned via a parameter between topological and trivial insulating phases, arguing that nontrivial topology has fingerprints in the spectrum of these excitons. The closely related hydrogen atom problem is well known to have a degeneracy due to a hidden symmetry, and the changes to the excitonic spectrum that we find can be understood as a result of breaking of this underlying symmetry due to the Berry phase. Furthermore, this phase is found to affect the spectrum in the topological parameter regime much more strongly than in the trivial regime. We first construct a semiclassical model of the system to develop qualitative intuition for the effects at play, then move to a more robust numerical simulation of the full quantum system, working with the Bernevig-Hughes-Zhang model of a 2D topological insulator.

cond-mat.mes-hall↗

arXiv2015

Repulsive Casimir force between Weyl semimetals

Weyl semimetals are a class of topological materials that exhibit a bulk Hall effect due to time-reversal symmetry breaking. We show that for the idealized semi-infinite case, the Casimir force between two identical Weyl semimetals is repulsive at short range and attractive at long range. Considering plates of finite thickness, we can reduce the size of the long-range attraction even making it repulsive for all distances when thin enough. In the thin-film limit, we study the appearance of an attractive Casimir force at shorter distances due to the longitudinal conductivity. Magnetic field, thickness, and chemical potential provide tunable nobs for this effect, controlling the Casimir force: whether it is attractive or repulsive, the magnitude of the effect, and the positions and existence of a trap and antitrap.

cond-mat.mes-hall↗

arXiv2015

Quantum interference phenomena in the Casimir effect

We propose a definitive test of whether plates involved in Casimir experiments should be modeled with ballistic or diffusive electrons--a prominent controversy highlighted by a number of conflicting experiments. The unambiguous test we propose is a measurement of the Casimir force between a disordered quasi-2D metallic plate and a three-dimensional metallic system at low temperatures, in which disorder-induced weak localization effects modify the well-known Drude result in an experimentally tunable way. We calculate the weak localization correction to the Casimir force as a function of magnetic field and temperature and demonstrate that the quantum interference suppression of the Casimir force is a strong, observable effect. The coexistence of weak localization suppression in electronic transport and Casimir pressure would lend credence to the Drude theory of the Casimir effect, while the lack of such correlation would indicate a fundamental problem with the existing theory. We also study mesoscopic disorder fluctuations in the Casimir effect and estimate the width of the distribution of Casmir energies due to disorder fluctuations.

quant-ph↗

arXiv2013

Non-analytic behavior of the Casimir force across a Lifshitz transition in a spin-orbit coupled material

We propose the Casimir effect as a general method to observe Lifshitz transitions in electron systems. The concept is demonstrated with a planar spin-orbit coupled semiconductor in a magnetic field. We calculate the Casimir force between two such semiconductors and between the semiconductor and a metal as a function of the Zeeman splitting in the semiconductor. The Zeeman field causes a Fermi pocket in the semiconductor to form or collapse by tuning the system through a topological Lifshitz transition. We find that the Casimir force experiences a kink at the transition point and noticeably different behaviors on either side of the transition. The simplest experimental realization of the proposed effect would involve a metal-coated sphere suspended from a micro-cantilever above a thin layer of InSb (or another semiconductor with large $g$-factor). Numerical estimates are provided and indicate that the effect is well within experimental reach.

cond-mat.mes-hall↗