Bulletin of the American Physical Society
50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 64, Number 4
Monday–Friday, May 27–31, 2019; Milwaukee, Wisconsin
Session N07: Quantum Dissipation and Localization |
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Chair: David Weiss, Penn State Room: Wisconsin Center 103AB |
Thursday, May 30, 2019 8:00AM - 8:12AM |
N07.00001: Quantum critical behavior at the many-body localization transition Julian Leonard, Matthew Rispoli, Alexander Lukin, Robert Schittko, Sooshin Kim, Eric M. Tai, Markus Greiner Phase transitions are driven by collective fluctuations of a system's constituents that emerge at a critical point. This mechanism has been extensively explored for classical and quantum systems in equilibrium, whose critical behavior is described by a general theory of phase transitions. The many-body localization (MBL) transition, however, occurs out-of-equilibrium and presents a fundamentally different type of phase transitions that defies this description and is not well understood. We present studies on the quantum critical behavior at the MBL transition and characterize its entanglement properties via its quantum correlations. We observe strong correlations, whose emergence is accompanied by the onset of anomalous diffusive transport throughout the system, and verify their critical nature by measuring their system-size dependence. The correlations extend to high orders in the quantum critical regime and appear to form via a sparse network of many-body resonances that spans the entire system. Our results unify the system's microscopic structure with its macroscopic quantum critical behavior, and they provide an essential step towards understanding criticality and universality in non-equilibrium systems. [Preview Abstract] |
Thursday, May 30, 2019 8:12AM - 8:24AM |
N07.00002: Exploring many-body-localization in the presence of local thermal bath Sooshin Kim, Matthew Rispoli, Alexander Lukin, Robert Schittko, Joyce Kwan, Julian Leonard, Markus Greiner We study the behavior of a many-body-localized (MBL) system when it is coupled locally with a quantum bath. Our system is a one-dimensional Bose-Hubbard chain in an optical lattice with an additional potential that provides both the disordered (MBL) and non-disordered (bath) regions that are coupled via a single-site. The microscopic access afforded by our quantum gas microscope allows us to obtain the site-resolved density correlations, von Neumann entropy, and penetration depth of the bath into the MBL region. We further investigate how these observables change for various bath sizes and disorder strengths. These studies allow us to characterize how many-body localization is affected by local contact with a quantum bath. [Preview Abstract] |
Thursday, May 30, 2019 8:24AM - 8:36AM |
N07.00003: MBL-mobile: Quantum engine based on many-body localization Nicole Yunger Halpern, Christopher White, Sarang Gopalakrishnan Many-body-localized (MBL) systems do not thermalize under their intrinsic dynamics. The athermality of MBL, we propose, can be harnessed for thermodynamic tasks. We illustrate this ability by formulating an Otto engine cycle for a quantum many-body system. The system is ramped between a strongly localized MBL regime and a thermal (or weakly localized) regime. The difference between the energy-level correlations of MBL systems and of thermal systems enables mesoscale engines to run in parallel in the thermodynamic limit, enhances the engine's reliability, and suppresses worst-case trials. We estimate analytically and calculate numerically the engine's efficiency and per-cycle power. The efficiency mirrors the efficiency of the conventional thermodynamic Otto engine. The per-cycle power scales linearly with the system size and inverse-exponentially with a localization length. The engine can be realized, e.g., with ultracold atoms in an optical lattice. This work introduces a thermodynamic lens onto MBL, which, having been studied much recently, can now be considered for use in thermodynamic tasks. [Preview Abstract] |
Thursday, May 30, 2019 8:36AM - 8:48AM |
N07.00004: Vortex recombination and energy dissipation in Fermionic superfluids Khalid Hossain, Michael Forbes, Konrad Kobuszewski, Piotr Magierski, Gabriel Wlazłowski The dynamics of quantized superfluid vortices underlies quantum turbulence. An accurate characterization of these can be obtained from a model called time-dependent Superfluid Local Density Approximation (TDSLDA). TDSLDA is computationally too expensive to simulate fermionic systems with macroscopic volume. To study dynamical processes like vortex recombination and energy dissipation, we propose using simpler Gross-Pitaevskii (GPE) like model called an Extended Thomas-Fermi (ETF) model. In this work, we simulate the Unitary Fermi Gas (UFG) with particular attention to energy dissipation and validate to what extent ETF can describe the dynamics. [Preview Abstract] |
Thursday, May 30, 2019 8:48AM - 9:00AM |
N07.00005: Dissipation Induced Structural Instability and Chiral Dynamics in a Quantum Gas Katrin Kroeger, Nishant Dogra, Manuele Landini, Lorenz Hruby, Francesco Ferri, Rodrigo Rosa-Medina, Tobias Donner, Tilman Esslinger Dissipation is an intrinsic part of any physical system and can cause undesired effects of decoherence or act as a weak perturbation to the Hamiltonian dynamics. However, the interplay of dissipative and unitary processes can give rise to dynamical phase transitions and lead to instabilities. In this work, we experimentally realize a synthetic quantum many-body system with controllable unitary and dissipative interactions [N. Dogra et al., arXiv 1901.05974]. Our experiment is based on a spinor Bose-Einstein-Condensate placed inside a high finesse optical cavity. The two orthogonal quadratures of the cavity light field coherently couple the atomic cloud to two modes with different spatial atomic configurations, which consist of a modulation of either atomic density or spin. The dispersive effect from the finite cavity losses mediates a dissipative chiral coupling between the two modes. Bringing unitary and dissipative couplings into competition allows us to explore the system’s macroscopic behavior at the boundary between stationary and non-stationary states. We observe chiral dynamics for dominating dissipative processes. Our observations can be explained by interpreting dissipation as a structure dependent force, in close analogy to mechanical non-conservative positional forces. [Preview Abstract] |
Thursday, May 30, 2019 9:00AM - 9:12AM |
N07.00006: Onset of thermalization in a Quantum Newton's Cradle Joshua Wilson, Neel Malvania, Jean-Felix Riou, Laura Zundel, Lin Xia, David Weiss Bosons trapped in a blue-detuned 2D optical lattice can be made to approximate the integrable Lieb-Liniger model, but the approximation is imperfect. So while integrability would constrain an out-of-equilibrium Lieb-Liniger gas from thermalizing, slight non-integrability in quasi-1D gases can lead to thermalization. We study such gasses (Quantum Newton’s cradles) with a range of initial energies and 2D lattice depths and measure the evolution of their total energy. After accounting for the effects of spontaneous emission and 3-body loss, we infer that there is evaporative cooling, which implies the onset of thermalization. [Preview Abstract] |
Thursday, May 30, 2019 9:12AM - 9:24AM |
N07.00007: Finite-temperature compressibility of disordered lattice bosons at unit filling Philip Russ, Mi Yan, Nicholas Kowalski, Laura Wadleigh, Vito Scarola, Brian DeMarco The disordered Bose-Hubbard model is a paradigm for strongly interacting bosons tunneling between adjacent sites of a disordered crystalline material. A complete picture for the disorder-driven, incompressible--to--compressible Mott-insulator--to--Bose-glass transition (which occurs for simultaneously strong interactions and strong disorder) is not fully understood. To probe this problem, we superimpose a cubic disordered optical lattice potential on Bose-Einstein condensates of $^{\mathrm{87}}$Rb atoms and measure the core compressibility by observing how disorder affects double occupancy. Our measurements indicate that a remnant of the zero-temperature phase boundary is visible at finite entropy-per-particle. Furthermore, the physics of this transition can be understood using a single-site disordered model, in contrast to the typical description consisting of rare regions in an infinite system. [Preview Abstract] |
Thursday, May 30, 2019 9:24AM - 9:36AM |
N07.00008: Moire Localization Biao Huang, W. Vincent Liu We discuss a new mechanism to realize the Anderson localization through the engineering of Moire superlattice potentials. Unlike in the usual Aubry-Andre models, the two lattice potentials producing the Moire pattern have exactly the same lattice geometry and wavelengths, but only mismatched up to a global rotation. We show that there are crucial differences between the commensurate and incommensurate Moire patterns, with the former one holding usual reconstructed Bloch waves while the latter one exponentially localized eigenstates. The unusual localization length and experimental signatures are also demonstrated. [Preview Abstract] |
Thursday, May 30, 2019 9:36AM - 9:48AM |
N07.00009: Excitation Energy Transport in Molecular Systems Coupled to a Thermal Environment Viktor Turner, Seth Rittenhouse We investigated potential coherence of exiton modes through photosynthetic structures, which may contribute to the high efficiency energy transport which has been observed experimentally. We modeled the system as excitations on a lattice coupled to a thermal environment. Using the quantum master equation, we explored the roles of nonlocal dephasing and incoherent drive on the efficiency of the energy transport through the system. [Preview Abstract] |
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