Superflow decay in a toroidal Bose gas: The effect of quantum and thermal fluctuations

TL;DR

This paper models the decay of superfluid currents in a toroidal Bose gas, highlighting the roles of quantum and thermal fluctuations and providing quantitative insights into temperature-dependent decay timescales.

Contribution

It introduces a comprehensive classical-field simulation approach that captures both quantum and thermal fluctuations, improving understanding of superflow decay in ultracold Bose gases.

Findings

Quantitative agreement with low-temperature experimental decay times

Decay timescales at higher temperatures match experimental order of magnitude

Identifies discrepancies at higher temperatures indicating need for further research

Abstract

We theoretically investigate the stochastic decay of persistent currents in a toroidal ultracold atomic superfluid caused by a perturbing barrier. Specifically, we perform detailed three-dimensional simulations to model the experiment of Kumar et al. in [Phys. Rev. A 95 021602 (2017)], which observed a strong temperature dependence in the timescale of superflow decay in an ultracold Bose gas. Our ab initio numerical approach exploits a classical-field framework that includes thermal fluctuations due to interactions between the superfluid and a thermal cloud, as well as the intrinsic quantum fluctuations of the Bose gas. In the low-temperature regime our simulations provide a quantitative description of the experimental decay timescales, improving on previous numerical and analytical approaches. At higher temperatures, our simulations give decay timescales that range over the same orders of magnitude observed in the experiment, however, there are some quantitative discrepancies that are not captured by any of the mechanisms we explore. Our results suggest a need for further experimental and theoretical studies into superflow stability.