Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session N3: 1D Quantum Gases |
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Chair: Randy Hulet, Rice University Room: 202 |
Thursday, June 6, 2013 10:30AM - 10:42AM |
N3.00001: Initial state dependence on the relaxation of out-of-equilibrium spin-1/2 systems Eduardo Torres-Herrera, Lea Santos Recently there has been great interest in simulating spin systems with cold atoms in optical lattices. Here, we show results for our studies of the relaxation process and the viability of thermalization in isolated one-dimensional quantum many-body systems described by spin-1/2 models. We show that the onset of thermal equilibrium depends on the interplay between initial states, observables and regimes. Our numerical studies are based on the spectrum analysis of the systems and on their long-time evolution after a quench. [Preview Abstract] |
Thursday, June 6, 2013 10:42AM - 10:54AM |
N3.00002: Quantum flutter versus Bloch oscillations in one-dimensional quantum liquids out of equilibrium Charles Mathy, Michael Knap, Eugene Demler We study the dynamics of an impurity of finite mass injected into a one-dimensional quantum liquid at zero temperature, either at finite velocity or at zero velocity with a force driving the impurity. We obtain accurate results using numerical simulations based on matrix product states, and find that in both cases, the impurity undergoes oscillations, however the physical mechanism is different: the driven impurity undergoes Bloch oscillations by following the ground state branch through dissipation, while the undriven impurity undergoes coherent quantum oscillations at an emergent energy scale, called quantum flutter in previous work, whose amplitude grows with increasing initial velocity. We find these results to be independent of whether the system is integrable or not, and robust to changes in the microscopics of the model, suggesting that they are universal. [Preview Abstract] |
Thursday, June 6, 2013 10:54AM - 11:06AM |
N3.00003: Damping of dipole oscillations of one-dimensional Bose gases induced by quantum phase slips Ippei Danshita Motivated by the experiments studying the transport of one-dimensional (1D) Bose gases in optical lattices, we analyze the dynamics of damped dipole oscillations of 1D Bose gases by means of numerically exact time-evolving block decimation method. We find a broad parameter region in which the damping rate of the oscillation is proportional to the nucleation rate of a quantum phase slip divided by the flow velocity and exhibits a power-law behavior with respect to the flow velocity. From this relation, we argue that the suppression of the 1D transport observed in the experiments is mainly due to quantum phase slips. We also suggest that the damping rate obeys a universal damping behavior at finite temperatures. [Preview Abstract] |
Thursday, June 6, 2013 11:06AM - 11:18AM |
N3.00004: Thermodynamics of ultracold Bose gases at a dimensional crossover Ralf Labouvie, Andreas Vogler, Vera Guarrera, Herwig Ott We have studied the thermodynamics of ultracold Bose gases in the crossover from a three-dimensional to a one-dimensional regime. In our experiment, we use a focused electron-beam to probe in situ atomic density distributions with high temporal and spatial resolution. Starting with a Bose-Einstein-Condensate in a single beam optical dipole trap we can create one-dimensional systems by loading the atoms in a two-dimensional blue-detuned optical lattice. With increasing strength of the lattices we go from a three-dimensional into a one-dimensional system. Furthermore we tune the interaction strengths of the one-dimensional quantum-gases from weak (quasi-condensate) to strong (Tonks-Girardeau). By measuring the density profiles and applying an inverse Abel-Transformation we extract the equation of states of these systems and characterize the crossover from the three-dimensional to the one-dimensional regime. [Preview Abstract] |
Thursday, June 6, 2013 11:18AM - 11:30AM |
N3.00005: Dynamical control of a quantum Kapitza pendulum in a spin-1 BEC Thai Hoang, Corey Gerving, Ben Land, Martin Anquez, Chris Hamley, Michael Chapman We demonstrate dynamic stabilization of an unstable strongly interacting quantum many-body system by periodic manipulation of the phase of the collective states. The experiment employs a spin-1 atomic Bose condensate that has spin dynamics analogous to a non-rigid pendulum in the mean-field limit. The condensate spin is initialized to an unstable (hyperbolic) fixed point of the phase space, where subsequent free evolution gives rise to spin-nematic squeezing\footnote{C.D. Hamley, \emph{et al.}, ``Spin-Nematic Squeezed Vacuum in a Quantum Gas,'' Nature Physics 8, 305-308 (2012).} and quantum spin mixing.\footnote{C.S. Gerving, \emph{et al.}, ``Non-equilibrium dynamics of an unstable quantum pendulum explored in a spin-1 Bose-Einstein condensate,'' Nature Communications 3, 1169 (2012).} To stabilize the system, periodic microwave pulses are applied that manipulate the spin-nematic fluctuations and limit their growth. The range of pulse periods and phase shifts with which the condensate can be stabilized is measured and compares well with a linear stability analysis of the problem.\footnote{T.M. Hoang, \emph{et al.}, ``Dynamic stabilization of a quantum many-body system.'' arXiv:1209.4363 (2012).} [Preview Abstract] |
Thursday, June 6, 2013 11:30AM - 11:42AM |
N3.00006: Collective Modes of One-Dimensional Bose Gases: From Few to Many Particles Lushuai Cao, R\"udiger Schmitz, Sven Kr\"onke, Peter Schmelcher We study the breathing oscillations of Bose gases in a one-dimensional harmonic trap via numerically exact simulations, and we focus on the crossover from few- to many-body systems. We firstly study the breathing properties of few-particle system (2-6 bosons) with varying the contact interaction strength, and reveal the transition from two-mode beating to single-mode breathing as well as breathing frequency shifting as the interaction strength increasing from zero to approaching infinity. We also present an extensive study of the breathing properties of systems covering a wide particle-number regime from few-body ($\sim$10 bosons) to many-body systems ($\sim$150 bosons). Even in the low interaction regime the numerically exact simulations show deviations with respect to the results obtained by mean-field approximations, which indicates the arising of beyond-mean-field effects in the low interaction regime. The numerically exact simulations are done by the Multi-layer Multi-Configurational Time-Dependent Hartree method for Bosons (ML-MCTDHB), which is developed particularly for the time propagation study of many-body system containing arbitrary bosonic species in various dimensions. [Preview Abstract] |
Thursday, June 6, 2013 11:42AM - 11:54AM |
N3.00007: One-Dimensional Bose Gases Out of Equilibrium Tim Langen, Maximilian Kuhnert, Michael Gring, Bernhard Rauer, David Adu Smith, Remi Geiger, Igor Mazets, Takuya Kitagawa, Eugene Demler, J\"org Schmiedmayer We will give an overview of our recent experiments on the quench dynamics and thermalization of isolated quantum systems. In a first experiment we coherently split a one-dimensional Bose gas. The time evolution following this quench leads to the establishment of a quasi-steady prethermalized state which we characterize in detail. Using time-resolved measurements of two-point correlation functions we further show that the strong correlations introduced by the quench decay according to a light-cone-like evolution. In a second series of experiments, we introduce a tunable tunnel coupling between the two gases. This allows us to explore a wide range of quench protocols with time-dependent tunnel couplings. [Preview Abstract] |
Thursday, June 6, 2013 11:54AM - 12:06PM |
N3.00008: Correlation functions of quasi-one-dimensional cold gases in well-defined spin states Vladimir Yurovsky Many-body states of quasi-one-dimensional atoms with zero-range interactions can be grouped into multiplets by the total spin, where two projections of the spin $1/2$ are attributed to the two internal states of each atom. Correlation functions, averaged over the spin multiplets, are expressed here in terms of characters of irreducible representations of the symmetric group. The characters were identified by Dirac [1] as the integrals of motion, related to the permutation symmetry. They can be explicitly expressed in terms of the total spin, corresponding to the irreducible representation. The spin multiplets can be populated using spin-dependent non-stationary potentials and identified by their average correlations. The well-defined spin states, being many-body entangled states, can find applications in quantum computations and metrology.\\[4pt] [1] P.A.M. Dirac, Proc. R. Soc. A {\bf 123}, 714 (1929). [Preview Abstract] |
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