Thermally activated phase slips of one-dimensional Bose gases in shallow optical lattices

TL;DR

This paper investigates how thermal fluctuations cause phase slips in one-dimensional Bose gases within shallow optical lattices, linking theoretical calculations with experimental observations of oscillation damping.

Contribution

It introduces a formula connecting phase-slip nucleation rates with dipole oscillation damping, validated by comparison with recent experimental data.

Findings

Thermally activated phase slips significantly contribute to oscillation damping.

The derived formula accurately predicts experimental damping rates.

Quantum phase slips are less dominant in the observed regime.

Abstract

We study the decay of superflow via thermally activated phase slips in one-dimensional Bose gases in a shallow optical lattice. By using the Kramers formula, we numerically calculate the nucleation rate of a thermally activated phase slip for various values of the filling factor and flow velocity in the absence of a harmonic trapping potential. Within the local density approximation, we derive a formula connecting the phase-slip nucleation rate with the damping rate of a dipole oscillation of the Bose gas in the presence of a harmonic trap. We use the derived formula to directly compare our theory with the recent experiment done by the LENS group [L. Tanzi, et al., Sci. Rep. {\bf 6}, 25965 (2016)]. From the comparison, the observed damping of dipole oscillations in a weakly correlated and small velocity regime is attributed dominantly to thermally activated phase slips rather than quantum phase slips.