Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session P24: Non-Equilibrium Physics in AMO Systems III |
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Sponsoring Units: DAMOP DCMP Chair: Michael Buchhold, Caltech Room: BCEC 159 |
Wednesday, March 6, 2019 2:30PM - 2:42PM |
P24.00001: Observation of the Higgs mode in the superfluid BEC-BCS crossover in Fermi gases Johannes Kombe, Alexandra Behrle, Timothy Harrison, Kuiyi Gao, Martin Link, Jean-Sebastien Bernier, Corinna Kollath, Michael Koehl Thanks to recent advances, investigating the non-equilibrium dynamics of interacting systems is now possible. Using time-dependent perturbations, one can probe from a different angle the mechanisms responsible for the collective phenomena present in correlated systems. Taking advantage of this progress, we investigate both theoretically and experimentally the evolution of a three-dimensional Fermi gas while the interaction strength is effectively modified. Our study, carried out on the BCS side, reveals various collective excitations. Interestingly, this approach highlights the presence of the Higgs mode. |
Wednesday, March 6, 2019 2:42PM - 2:54PM |
P24.00002: Constrained Hilbert Spaces and Many-body Scars in a Landau Level Sanjay Moudgalya, Nicolas Regnault, B Andrei Bernevig We study a "pair-hopping" model that arises within a Landau level in the thin-torus limit of the quantum Hall effect. At filling \nu = 1/3, we show that the model maps on to the "PXP model", a constrained model for the Rydberg atom chain known to exhibit quantum many-body scars (ETH-violating states in the middle of the spectrum). Further, for general fillings factors \nu = p/(2p+1), we show the mapping onto spin-chains with constrained Hilbert spaces that share several features with the PXP model, including the presence of many-body scars and slow thermalization of particular product states. Finally, we investigate the stability of scars in the presence of electrostatic and long-range hopping terms that are always present in the quantum Hall setup. |
Wednesday, March 6, 2019 2:54PM - 3:06PM |
P24.00003: Computing thermalization times and hydrodynamic modes from microscopic quantum dynamics Ehud Altman, Xiangyu Cao, Daniel Parker, David Huse
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Wednesday, March 6, 2019 3:06PM - 3:18PM |
P24.00004: Entanglement dynamics with diffusive transport Tibor Rakovszky, Frank Pollmann, Curt W Von Keyserlingk We investigate how the incoherent (diffusive) transport of conserved quantities affects the growth of entanglement in generic non-integrable systems. We develop a general picture by considering random unitary circuit dynamics with a U(1) symmetry which allows for an efficient numerical treatment and, in a certain coarse-grained limit, leads to a simple equation of motion for the entanglement entropy, which takes the form of a random, space-time dependent surface growth model. Based on this we argue that an initial state with large-scale inomogeneities in the conserved densities gives rise to an uneven entanglement profile across the system, with features whose "height" and "width" both grow as t1/2 . We confirm this prediction by numerically investigating a variety of different initial states, both in the random circuit model away from the coarse-grained limit, and in a deterministic spin chain. Moreover, we investigate the effects of charge-fluctuation and find that these can lead to a slow-down in entanglement growth even for spatially homogenous states. |
Wednesday, March 6, 2019 3:18PM - 3:30PM |
P24.00005: Dynamical Phase Transitions in a 2D Quantum Dimer Model Johannes Feldmeier, Michael Knap, Frank Pollmann The study of dynamical properties in systems with local constraints has attracted a lot of interest, spurred by experiments with Rydberg blockaded atoms, that naturally implement constrained many-body models. |
Wednesday, March 6, 2019 3:30PM - 3:42PM |
P24.00006: Exact long-time evolution of spinless fermion systems from a highly correlated state Kristof Harms, Lorenzo Cevolani, Stefan Kehrein, Salvatore Manmana We investigate the dynamics of a one-dimensional system of spinless fermions, which is initially prepared in a highly correlated groundstate of an interacting Hamiltonian. In particular, for a global quench that turns off the interaction, we evolve the initial state obtained via density matrix renormalisation group (DMRG) using analytical solutions of the equations of motion. This allows us to reach arbitrary times. We examine features of the dynamics of density-density correlations and susceptibilities on several time scales. Shortly after the quench, we identify, in addition to the typical lightcone-behavior, periodic recurrences of the initial correlations outside the lightcone. At very long times, we use our approach to investigate the Fluctuation-Dissipation theorem in this strong nonequilibrium situation. |
Wednesday, March 6, 2019 3:42PM - 3:54PM |
P24.00007: Pokrovsky-Talapov transition with two Ramsey-tunnel-coupled 1D-Bose gases Valentin Kasper, Jamir Marino, Si Cong, Joerg Schmiedmayer, Eugene Demler The high flexibility of ultracold atoms allows for the design, control and investigation of quantum matter. In this work we consider two one-dimensional Ramsey tunnel-coupled Bose gases and show that the low-energy effective theory of this system is described by the quantum Prokrovsky-Talapov model. We study the ground state with variational wave-functions and elaborate on the modification of the quantum phase transition due to a finite system size. Finally, we consider the non-equilibrium evolution determined by quench from an uncoupled Bose gases to the Ramsey tunnel coupled case and predict the experimental relevant evolution of phase correlations. |
Wednesday, March 6, 2019 3:54PM - 4:06PM |
P24.00008: Dynamics of fractional Chern insulators under global quantum quenches Johannes Motruk, Joel Moore Recent progress in the control of synthetic gauge fields in optical lattices has brought the realization of strongly correlated topological phases in cold atom experiments within reach. Due to longer time scales compared to solid state systems, the quantum dynamics in such setups are experimentally more amenable and may encode information about the topological properties of the state. In this work, we investigate quantum quenches between Hamiltonians with a fractional Chern insulator (FCI) ground state and topologically trivial Hamiltonians. Focusing on the experimentally realized Hofstadter model, we study the post-quench behavior of various quantities such as edge currents, Hall response and Loschmidt echo and determine how they display signatures of the topologically ordered initial state. Furthermore, we comment on implications for dynamically detecting FCI states in cold atom experiments. |
Wednesday, March 6, 2019 4:06PM - 4:18PM |
P24.00009: Loschmidt Amplitude and Work Distribution in Quenches of the Sine-Gordon Model Colin Rylands, Natan Andrei The Sine-Gordon model is ubiquitous in low-dimensional physics, with applications that range from cold atom and strongly correlated systems to quantum impurities. In this talk we present a study of its non-equilibrium dynamics using the quantum quench protocol. By means of the Bethe Ansatz we calculate exactly the Loschmidt amplitude, the fidelity and work distribution characterizing the quench for different values of the interaction strength. Some universal features are noted as well as an interesting duality relating quenches in different parameter regimes of the model. |
Wednesday, March 6, 2019 4:18PM - 4:30PM |
P24.00010: Quench dynamics across topological quantum phase transitions Shiuan-Fan Liou, Kun Yang We study the dynamics of systems quenched through topological quantum phase transitions and investigate the behavior of the bulk and edge excitations with various quench rates. Specifically, we consider the Haldane model and checkerboard model in slow quench processes with distinct band-touching structures leading to topology changes. The generation of bulk excitations is found to obey the power-law relation Kibble-Zurek and Landau-Zener theories predict. However, an anti-Kibble-Zurek behavior is observed in the edge excitations. The mechanism of excitation generation on edge states is revealed, which explains the anti-Kibble-Zurek behavior. |
Wednesday, March 6, 2019 4:30PM - 4:42PM |
P24.00011: Phonon Coupling's Role in the Non-Equilibrium Dynamics of a Quasicondensate Ryan Plestid, Duncan O'Dell Cold atoms loaded into cigar shaped traps can realize the Lieb Liniger model where the effective 1-D coupling constant depends both on the three-dimensional scattering length of the atomic species, and on the trap's transverse frequency. By performing a quantum quench of the transverse trapping frequency, non-equilbirum density and phase dynamics can be induced. In the low temperature regime, these dynamics are well characterized by Bogoliubov theory, however at higher temperatures intermode (i.e. phonon-phonon) coupling can become important. In this work we report on classical field simulations of a quasi condensate undergoing the quench protocol outlined above, and comment on the consequences of intermode coupling both for damping, and energy transfer. |
Wednesday, March 6, 2019 4:42PM - 4:54PM |
P24.00012: Universality of Particle and Spatial Entanglement After an Interaction Quench in a Tomonaga-Luttinger Liquid Adrian Del Maestro, Bernd Rosenow While the post-quench linear growth of entanglement entropy under a spatial biparition is well understood in terms of the propagation of quasiparticles, very little is known about entanglement dynamics under a bipartition into groups of particles. This so-called particle entanglement entropy is constructed from the familiar n - body reduced density matrix and is thus sensitive to both interactions and particle statistics while not possessing any externally imposed length scale. In this talk we present new results for the long-time limit of the n-particle entanglement after a global interaction quench in a Tomonaga-Luttinger liquid. By considering values of n up to 6 we uncover a previously unknown connection between the particle and spatial entanglement after a quench and discuss how it may be analyzed within the framework of bosonization. |
Wednesday, March 6, 2019 4:54PM - 5:06PM |
P24.00013: Nucleation of superfluid-light domains in a quenched dynamics Joaquin Figueroa, Jose Rogan, Juan Alejandro Valdivia, Miguel G Kiwi, Guillermo Romero, Felipe Torres Strong correlation effects emerge from light-matter interactions in coupled resonator arrays, such as the Mott-insulator to the superfluid phase transition of atom-photon excitations. We demonstrate that the quenched dynamics of a finite-sized array of coupled resonators induces a first-order like phase transition. The latter is accompanied by domain nucleation that can be used to manipulate the photonic transport properties of the simulated superfluid phase; this, in turn, leads to an empirical scaling law. This universal behavior emerges from light-matter interaction and the topology of the array. The validity of our results over a wide range of complex architectures might lead to a promising device for use in quantum scaled quantum simulations. |
Wednesday, March 6, 2019 5:06PM - 5:18PM |
P24.00014: The multifractal X-ray edge problem Angkun Wu, Sarang Gopalakrishnan, Jed Pixley We will discuss the nature of the X-ray edge problem when the single particle eigenstates are multifractal. We focus on the case where the many-body wavefunction is composed of single particle eigenstates that are generated from the Aubry-Andre model at its critical point, and introduce a local impurity via an instantaneous quench at time t. We find that the orthogonality catastrophe remains between the pre and post quench wavefunctions where the average wavefunction overlap vanishes in a power law fashion as a function of the system size. This power law is markedly distinct from the plane wave limit, with a much slower decay. This behavior is also manifested in the distribution of wavefunction overlaps, where the overlap distribution becomes significantly broad at the critical point of the Aubry-Andre model. We also focus on the core-hole Green function, which effectively translates this phenomena to the time domain and find a long-time power law decay on average, with its distribution approaching the distribution of wavefunction overlaps in the long time limit. Despite focusing on the Aubry-Andre model, we invoke the universality of the single particle wavefunctions to argue that our results are generally applicable to other problems with multifractal wavefunctions. |
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