We study the dynamical depinning following a sudden turn off of an optical lattice for a gas of impenetrable bosons in a tight atomic waveguide. We use a Bose-Fermi mapping to infer the exact quantum dynamical evolution. At long times, in the thermodynamic limit, we observe the approach to a non-equilibrium steady state, characterized by the absence of quasi-long-range order and a reduced visibility in the momentum distribution. Similar features are found in a finite-size system at times corresponding to half the revival time, where we find that the system approaches a quasi-steady state with a power-law behaviour.
We determine the finite temperature phase diagram of two dimensional bosons with two hyperfine (pseudo-spin) states coupled via Rashba-Dresselhaus spin-orbit interaction using classical field Monte Carlo calculations. For anisotropic spin-orbit coupling, we find a transition to a BerenzinskiiKosterlitz-Thouless superfluid phase with quasi-long range order. We show that the spin-order of the quasi-condensate is driven by the anisotropy of interparticle interaction, favoring either a homogeneous plane wave state or stripe phase with broken translational symmetry. Both phases show characteristic behavior in the algebraically decaying spin density correlation function. For fully isotropic interparticle interaction, our calculations indicate a fractionalized quasi-condensate where the mean-field degeneracy of plane wave and stripe phase remains robust against critical fluctuations. In the case of fully isotropic spin-orbit coupling, the circular degeneracy of the single particle ground state destroys the algebraic ordered phase in the thermodynamic limit, but a cross-over remains for finite size systems.Introduction. The coupling of artificial gauge fields to ultracold atomic gases [1] has opened the possibility of studying spin-orbit coupled Bose gases [2][3][4][5] where translational symmetry may be broken spontaneously in the superfluid ground state [6]. At the mean-field level, spin-orbit coupling (SOC) introduces degenerate ground states expected to enhance fluctuation effects and giving rise to new, exotic quantum phases. The occurrence and nature of finite temperature transitions in these systems have not yet been fully established [7][8][9][10][11][12].In the following we consider a two-dimensional homogeneous gas of Rashba-Dresselhaus spin-orbit coupled bosons. Mean-field calculations [10-14] indicate a Bose condensed ground state of a single plane wave with nonvanishing momentum or a linear superposition of two plane waves with opposite momenta, called plane wave state (PW) and stripe phase (SP), respectively. For spinindependent particle interaction, PW and SP remain degenerate at the mean-field level. In addition, in the case of isotropic SOC, ground states with momenta lying on a circle are connected by symmetry. These degeneracies may be broken by classical or quantum fluctuations.In this work we explore the phase diagram using classical field Monte Carlo calculations. We show that for anisotropic SOC, the systems undergoes a KosterlitzThouless phase transition from a normal to superfluid state. In the superfluid state, the single particle density matrix decays algebraically and directly reflects the PW/SP character of the mean-field ground state. In the limit of isotropic interparticle interaction, the PW/SP degeneracy is unaffected by the transition. Thus, at large but finite system sizes, fragmentation [15] of the condensate occurs. In the case of isotropic SOC, we show that the transition temperature decreases with increasing system size due to the increasing number of degenerate mean-field ground s...
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