Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session B33: Quantum Quenches and Integrability |
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Sponsoring Units: DCMP Chair: Ke Wang, University of Chicago Room: Room 225 |
Monday, March 6, 2023 11:30AM - 11:42AM |
B33.00001: Detecting and characterising dynamical quantum phase transitions through higher moments Ian McCulloch One conception of a dynamical quantum phase transition (DQPT) is the appearance of non-analyticies in the return rate (Loschmidt Echo), which is the overlap of an initial |
Monday, March 6, 2023 11:42AM - 11:54AM |
B33.00002: A Dynamical Bulk-Boundary Correspondence for Dynamical Quantum Phase Transitions in Topological Matter Nicholas Sedlmayr We study the Loschmidt echo for quenches in open one-dimensional lattice models with symmetry protected topological phases. For quenches where dynamical quantum phase transitions do occur we find that cusps in the bulk return rate at critical times are associated with sudden changes in the boundary contribution. For our first main example, the Su-Schrieffer-Heeger model, we show that these sudden changes are related to the periodical appearance of two eigenvalues close to zero in the dynamical Loschmidt matrix. We demonstrate, furthermore, that the structure of the Loschmidt spectrum is linked to the periodic creation of long-range entanglement between the edges of the system. Generalisations to more general systems, higher dimensional topological matter, and higher order topology are also discussed. |
Monday, March 6, 2023 11:54AM - 12:06PM Author not Attending |
B33.00003: Quantum thermodynamics of strongly correlated systems Vladimir Ohanesjan, Yevheniia Cheipesh, Nikolay Gnezdilov, Andrei Pavlov, Koenraad Schalm We study tunneling quenches when a hot many-body quantum system is brought into instantaneous contact with a cold many-body quantum system. The dynamics of such systems can be understood as a combination of early-time von Neumann entropy gain and late-time energy relaxation. We show that at the shortest timescales there is an energy increase in each system linked to the entropy gain and supported by the collective binding energy between the systems. Counterintuitively to the classical expectation, this implies that also the hotter of the two subsystems generically experiences an initial energy increase when brought into contact with a colder system. We explain this early time energy gain with a quantum thermodynamical relation that holds even for systems out of equilibrium and, in the limit where the energy relaxation overwhelms the quantum correlation build-up, reduces to classical behavior. We use both, strongly correlated SYK systems and mixed field Ising chains with a tunneling quench to exhibit these characteristics and study the contribution of quantum correlations to the von Neumann entropy. Interestingly, we discover that the energy dynamics of an Ising model around the quantum critical point have similar qualitative behavior to a strongly interacting SYK system. |
Monday, March 6, 2023 12:06PM - 12:18PM |
B33.00004: Non-Equilibrium Dynamics of a Quenched BEC: Complex Pathways to thermalization Ke Wang, Han Fu, Cheng Chin, Kathryn Levin We study the quantum dynamics of an isolated two-dimensional (2D) bosonic system involving a Bose-Einstein condensate (BEC) which is quenched to a highly non-equilibrium state. This issue is relevant to the general state preparation of BECs in higher bands. The dynamical pathways involve an initial formation of a well-organized ring-shape condensate which is consistent with the recently proposed theory of inflationary dynamics[Nature Physics 14 269]. We show how and why this ring-phase subsequently disorders into a cloud state characterized by a large number of bosonic pairs which proliferate and occupy an extended, but a confined region in the Brillouin zone. The associated wavefunction has an intrinsic many-body nature and at long time scales, thermalization and recondensation are shown to follow. We analyze the mechanism leading to this recondensation establishing its relation to a nonlinear kinetic Boltzman equation and building on the analogy with weak turbulence and resonant four-wave processes. Numerical simulations from the Gross Pitaevskii Equation yield these same dynamical pathways and support the theoretical approach described above. |
Monday, March 6, 2023 12:18PM - 12:30PM |
B33.00005: Tracking the Relaxation of Disordered Interacting Systems under an Interaction Quench Eric Dohner, Herbert Fotso, Hanna Terletska Disorder is known to play a nontrivial role in the non-equilibrium dynamics of many-particle systems. We use the recently developed non-equilibrium DMFT+CPA formalism[1] to characterize the relaxation of disordered interacting systems described by the Anderson-Hubbard model under an interaction quench. Using this effective-medium approach, we calculate, for different interaction quenches and disorder strengths, the distribution functions as the system evolves in time. This allows us to characterize the effective temperature after the quench and analyze the effects of the interplay between disorder and the Coulomb interaction on the relaxation. We find that disorder attenuates the heating of the system across the interaction quench. |
Monday, March 6, 2023 12:30PM - 12:42PM |
B33.00006: Real-time scattering dynamics in (1+1)D QED: from tensor networks to quantum circuits Ron Belyansky, Seth P Whitsitt, Niklas Mueller, Ali Fahimniya, Elizabeth R Bennewitz, Zohreh Davoudi, Alexey V Gorshkov We study the real time dynamics of high-energy particle collisions in the massive Schwinger model, a relativistic quantum field theory describing quantum electrodynamics (QED) in (1+1)D. We use infinite-matrix-product-states allowing the construction of proper wavepackets of quasiparticles, as well as the determination of the particle content of the post-collision state. We focus on two regimes near the confinement-deconfinment phase transition which give rise to qualitatively different interactions between charges: repulsive short-range, and confining long-range. Those regimes give rise to different scattering behaviour, allowing to probe different phenomena such as inelastic particle pair production, string breaking, and recombination. We also propose an analog implementation of the model using superconducting quantum circuits. The bosonized version of the model can be realized with a simple circuit and minimal ingredients, paving the way towards analog quantum simulation of (1+1)D quantum field theories beyond what is possible classically. |
Monday, March 6, 2023 12:42PM - 12:54PM |
B33.00007: Many Body Density of States of a system of non interacting fermions Gregoire Ithier, Rémi Lefèvre, Krissia d Zawadzki Originally considered in the context of nuclear physics by Hans Bethe [1], the problem of calculating a Many Body Density of States (MBDoS) has been eclipsed by the success of mean field theories. Indeed, within this framework, the concept of quasi particle has focused attention on single or few bodies densities of states, in order to explain equilibrium and transport properties of myriads of condensed matter systems. |
Monday, March 6, 2023 12:54PM - 1:06PM |
B33.00008: Weak perturbations of integrable models Federica Maria Surace, Olexei I Motrunich A quantum integrable system slightly perturbed away from integrability is typically expected to thermalize on timescales of order τ∼λ-2, where λ is the perturbation strength. We here study classes of perturbations that violate this scaling, and exhibit much longer thermalization times τ∼λ-2k where k>1 is an integer. Systems with these ``weak integrability breaking'' perturbations have an extensive number of quasi-conserved quantities that commute with the perturbed Hamiltonian up to corrections of order λk. We demonstrate a systematic construction to obtain families of such weak perturbations of a generic integrable model for arbitrary k. We then apply the construction to various models, including the Heisenberg, XXZ, and XYZ chains, the Hubbard model, models of spinless free fermions, and the quantum Ising chain. Our analytical framework explains the previously observed evidence of weak integrability breaking in the Heisenberg and XXZ chains under certain perturbations. |
Monday, March 6, 2023 1:06PM - 1:18PM |
B33.00009: Tunable anomalous diffusion in anisotropic quantum spin chains from correlated initial states Hansveer Singh Despite only hosting ballistically propagating quasiparticles, integrable systems can display diffusive transport at high temperatures. This diffusive behavior originates from the fact that fluctuations at high temperatures satisfy the central limit theorem. In this work, we examine the transport properties of anisotropic integrable spin chains in initial states whose fluctuations do not satisfy the central limit theorem. These so-called correlated initial states have fluctuations characterized by an exponent, w, known as the wandering exponent. We show that one can tune transport from subdiffusion to superdiffusion by changing the wandering exponent and provide a procedure to generate correlated initial states that will give a wandering exponent that either leads to subdiffusive, diffusive, or superdiffusive transport. |
Monday, March 6, 2023 1:18PM - 1:30PM |
B33.00010: Integrable Attractors in the Adiabatic Landscape of Chaotic Systems Hyeongjin Kim, Anatoli S Polkovnikov Adiabaticity has been extensively used in studying quantum chaos and integrability in the past decades. In this talk, we consider the adiabatic landscape of nonintegrable, many-body quantum systems with two coupling parameters that are comprised of both integrable and nonintegrable regimes. We find that integrable regions behave as attractors within the manifold defined by the quantum geometric tensor and observe universal behavior in the adiabatic flow towards integrability. |
Monday, March 6, 2023 1:30PM - 1:42PM |
B33.00011: Confinement of sine-Gordon solitons in a perturbed sine-Gordon model Yicheng Tang, Ananda Roy The quantum sine-Gordon model is one of the paradigmatic models of an integrable quantum field theory (QFT). When perturbed by a higher harmonic, the model is no longer integrable. However, it exhibits a rich set of non-perturbative phenomena ranging from confinement of sine-Gordon solitons to an Ising-type phase transition. In this work, we numerically analyze the confinement of sine-Gordon solitons using the XYZ spin-chain regularization for the model. To that end, we consider a global quantum quench and compute the time dependence of the correlation functions and the entanglement entropy using the time evolution block decimation technique. The presence of the perturbation leads to the formation of mesonic bound states akin to what happens in t'Hooft's 1+1D model of quantum chromodynamics and constitutes a rich generalization of the analogous phenomena in the quantum Ising model. We compute the mass spectra of the mesons numerically. We perform semi-classical analytic computations at the free-fermion point and verify our numerical computations with the analytical predictions. |
Monday, March 6, 2023 1:42PM - 1:54PM |
B33.00012: OTOCs and domain wall relocalisation in transverse field Ising chains Philippe Suchsland, Roderich Moessner, Vedika Khemani, Benoit Doucot We study order parameters and out-of-time-ordered correlators (OTOCs) for a wide variety of transverse field Ising chains: classical and quantum, clean and disordered, integrable and generic. The setting we consider is that of a quantum quench. We find a remarkably rich phenomenology, ranging from stable periodic to signals decaying with varying rates. This variety is due to a complex interplay of dynamical constraints (imposed by integrability and symmetry) which thermalisation is subject to. In particular, a process we term dynamical domain wall relocalisation provides a long-lived signal in the clean, integrable case, which can be degraded by the addition of disorder even without interactions. Our results shed light on a proposal to use an OTOC specifically as a local dynamical diagnostic of a quantum phase transition even when evaluated in a state with an energy density corresponding to the paramagnetic phase. |
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