Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session C24: NonEquilibrium Physics in AMO Systems IFocus

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Sponsoring Units: DAMOP DCMP Chair: Norman Yao, University of California, Berkeley Room: BCEC 159 
Monday, March 4, 2019 2:30PM  3:06PM 
C24.00001: Making Matter from Light: Photon Mott Insulators and Topological Fluids Invited Speaker: Jonathan Simon Recent developments in quantum optics have enabled strong interactions between individual photons. I will describe work at the University of Chicago harnessing these tools to assemble quantum matter from light: in a collaboration between the Simon and Schuster labs, we have demonstrated dissipative stabilization of a Mott insulator of microwave photons, trapped in an array of transmon qubits; in the Simon lab we have demonstrated that a twisted optical resonator generates artificial magnetic fields for photons trapped within it; we have now employed Rydberg atoms to mediate interactions between these photons and are exploring topological fluids of light. From thermodynamics of driven equilibria to microscopy of entangled systems, photonic materials provide unique opportunities in fewtomany body physics. 
Monday, March 4, 2019 3:06PM  3:18PM 
C24.00002: Dynamically Tuning One Dimensional Systems Across Quantum Phase Transitions: Classical and Quantal Defects. Andrew Millis, Dante Kennes Infinitesystem time dependent density matrix renormalization group and Loschmidtamplitude methods are used to analyse the physics occurring when a one dimensional system is dynamically tuned across a quantum phase transition, either by an ac (`Floquet') drive with time vary amplitude or a simple ramp in Hamitloniian parameters. Tuning the XXZ model between two points in the gapped phase introduces classical defects leading to exponentially decaying correlations as expected; tuning between two points in the gapless phase produces excitations which do not destroy the longdistance powerlaw behavior, and tuning across the phase transition produces quantum phase slips which appear in pairs and then annihilate. Loschmidt methods are used to interrogate the wave function obtained after (one or multiple) ramps across the critical point of the transverse field quantum Ising model, leading to new understanding of the population of the defects created and of the importance of quantum coherence. Portions of this work were performed in collaboration with A. Ron. A. della Torre, D. Hsieh and C. Karrasch. 
Monday, March 4, 2019 3:18PM  3:30PM 
C24.00003: Nonequilibrium Mass Transport in the 1D FermiHubbard Model Jan Stolpp, Sebastian Scherg, Thomas Kohlert, Jacek Herbrych, Pranjal Bordia, Ulrich Schneider, Fabian HeidrichMeisner, Immanuel Felix Bloch, Monika Aidelsburger We report on the results of a combined experimental and numerical study of nonequilibrium dynamics of ultracold fermions in a 1d lattice induced by quenching the trapping potential to zero [1]. This leads to an expansion of the cloud in a homogeneous lattice under the influence of interactions. For initial states with a significant admixture of doublons in a sea of singlons, we observe a dynamical demixing of fast expanding singlons from doublons that remain in the center of the system. We interpret this as evidence for fermionic quantum distillation [2]. For initial product states of one fermion per site and random spin orientations, we study the asymptotic expansion velocity. Compared to bosons [3], these velocities depend only very weakly on the interaction strength. We explain this observation by the fact that the Pauli principle significantly limits the amount of interaction energy that can be generated for fermions as compared to bosons. 
Monday, March 4, 2019 3:30PM  3:42PM 
C24.00004: Universal Aspects of Operator Thermalization in Hamiltonian Dynamics Daniel Parker, Xiangyu Cao, Ehud Altman The longtime behavior of observables in thermalizing quantum systems can often be captured through hydrodynamics, involving just a few local quantities. A key question in quantum dynamics is to derive such behavior from the microscopic behavior and predict quantities such as diffusion coefficients or conductivities. We describe a conjectural form for superoperator Green's functions in thermalizing systems at infinite temperature in any dimension. The conjecture is supported by numerical calculations for a broad range of thermalizing manybody models and exact analytic results for largeq SYK models. The universal asymptotic form of the Green's function suggests an efficient numerical technique for extracting diffusion coefficients of operators in strongly interacting systems. Additionally, the conjecture implies some 'universal' behavior of operators under Hamiltonian dynamics. 
Monday, March 4, 2019 3:42PM  3:54PM 
C24.00005: Observation of Dynamical Quantum Phase Transition in Antiferromagnetic Spinor BoseEinstein
Condensates in a short time region LiYuan Qiu, Haoxiang Yang, Tian Tian, Haiyu Liang, anjun chu, Yanbin Yang, Yingmei Liu, Luming Duan In this work, we show direct evidence of the dynamical quantum phase transition(DQPT) in antiferromagnetic spin1 Na BoseEinstein condensate system. Initially, the spinor1 BEC is at its ground state with quadratic Zeeman coeefficient q=11.2Hz where all atoms are in F=1, m_{F}=0〉 state, i.e. the fraction of spin0 atoms ρ_{0} is 1, then at t=0, the q suddenly changed to a q_{f }and the BEC will evolve variable times at this q_{f }. To observe DQPT, first minimum dip depth (A_{dip}) of ρ_{0}(t) is choosen to be a new order parameter. The experimental result shows that once the final quadratice Zeeman coefficient q_{f} crossed the transiton point, ρ_{0}(t) will shows large fluctuation and A_{dip} will arise abruptly. Futher, the dip depths A_{dip} under different quenched parameters q_{f} shows similar behavior with the long time average ρ_{0}(t) which indicates the dynamical quantum phase transitions across the critical point. 
Monday, March 4, 2019 3:54PM  4:06PM 
C24.00006: Exponentially fast dynamics of chaotic quantum manybody systems Lea Santos, Fausto Borgonovi, Felix Izrailev We demonstrate analytically and numerically that in isolated quantum systems of many interacting particles, the number of manybody states participating in the evolution after a quench increases exponentially in time, provided the eigenstates are delocalized in the energy shell. The rate of the exponential growth is defined by the width Γ of the local density of states (LDOS) and is associated with the KolmogorovSinai entropy for systems with a well defined classical limit. In a finite system, the exponential growth eventually saturates due to the finite volume of the energy shell. We estimate the time scale for the saturation and show that it is much larger than the characteristic decay time of the initial state 1/Γ. Numerical data obtained for a twobody random interaction model of bosons and for a dynamical model of interacting spin1/2 particles show excellent agreement with the analytical predictions. 

C24.00007: ABSTRACT WITHDRAWN

Monday, March 4, 2019 4:18PM  4:30PM 
C24.00008: Spin drag in a onedimensional quantum wire AnneMaria Visuri, Thierry Giamarchi The transport of spin, instead or charge, is the basis of the field of spintronics. Besides in condensed matter, spin transport has recently been explored in experiments with ultracold atoms which allow spinselective control. A central phenomenon in the transport of spin current is spin drag, where a chemical potential bias on one spin component induces the transport of the other component via interactions. For attractive contact interactions, the ground state of fermions in one dimension is a singlet superfluid, and spin drag is due to pairing of fermions with opposite spin. This was recently observed in a quantum point contact setup [1]. Motivated by recent transport experiments with ultracold atoms [1, 2], we investigate analytically and numerically the possibility of spin drag of repulsively interacting fermions in a onedimensional wire, where the ground state is a spin density wave. 
Monday, March 4, 2019 4:30PM  4:42PM 
C24.00009: Perfect oscillatory dynamics from quantum manybody scars Soonwon Choi, Christopher J Turner, Alexios Michailidis, Wen Wei Ho, Hannes Pichler, Xiaoliang Qi, Dmitry Abanin, Maksym Serbyn, Zlatko Papic, Mikhail Lukin The concept of quantum manybody scars  atypical, nonergodic energy eigenstates of an otherwise ergodic manybody system  was recently introduced to explain the surprising longlived oscillations observed in an interacting, constrained spin chain following a quantum quench. Here, we provide numerical evidence that a suitable, quasilocal deformation of the system leads to a dramatic increase of the lifetime of the oscillations, even possibly allowing them to last for an indefinitely long time. We show that this seemingly perfect oscillatory dynamics can be understood via an emergent large SU(2)spin undergoing precession, contained within a special subspace of the manybody Hilbert space, while the rest of the system remains ergodic. The presence of such dynamics severely constrains the structure of certain energy eigenstates in the thermodynamic limit. Furthermore, we introduce a toy model which captures the salient features of quantum manybody scarring. 
Monday, March 4, 2019 4:42PM  4:54PM 
C24.00010: Cooperative Breakdown of the Oscillator Blockade in the Dicke Model Florentin Reiter, Thanh Long Nguyen, Jonathan Home, Susanne F Yelin Spinboson models provide an interaction between atoms and harmonic oscillators and lie at the heart of quantum science. The superradiant phase transition in the Dicke model [1] constitutes a prime example of a nonequilibrium phase transition which has recently been realized experimentally [2]. 
Monday, March 4, 2019 4:54PM  5:06PM 
C24.00011: WITHDRAWN ABSTRACT

Monday, March 4, 2019 5:06PM  5:18PM 
C24.00012: Hydrodynamic behavior of noninteracting quantum particles in presence of dephasing Oles Shtanko, Seth Lloyd In quantum transport problems, thermal environment plays an important role. We demonstrate that additionally to suppressing transport via dephasing, the environment is able to induce new dynamic effects absent in an isolated system. In particular, we show that single particle or gas of free particle in presence of stochastic environment exhibits a formation of vortices and Poiseuille flow, the effects mainly considered as hydrodynamic behavior. We provide a detailed analysis of the phenomenon and derive equations for quasiviscous flow. The environmentally induced quantum viscosity suggests new possible transport regimes accessible in solidstate devices, isolated atomic systems, and photonic quantum simulators. 
Monday, March 4, 2019 5:18PM  5:30PM 
C24.00013: Scalling theory of quantum ratchet in low temperature limit Keita Hamamoto, Takamori Park, Hiroaki Ishizuka, Naoto Nagaosa Directionality of responses in noncentrosymmetric materials is a central issue in condensed matter physics. The quantum dynamics of particles in an asymmetric washboard potential with dissipation is a typical system. 
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