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

by Zain Mehdi, Ashton S. Bradley, Joseph J. Hope, Stuart S. Szigeti

Submission summary

As Contributors: Ashton Bradley · Zain Mehdi
Arxiv Link: (pdf)
Date accepted: 2021-09-28
Date submitted: 2021-09-17 02:52
Submitted by: Mehdi, Zain
Submitted to: SciPost Physics
Academic field: Physics
  • Atomic, Molecular and Optical Physics - Theory
  • Quantum Physics
Approaches: Theoretical, Computational


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.

Published as SciPost Phys. 11, 080 (2021)

List of changes

Minor grammatical changes across the manuscript.
-Minor changes to abstract: overview of discrepancy analysis shortened significantly.
1 Introduction
-Paragraph 5 has been restructured slightly to emphasize the need for first-principles modeling of the experiment.
2 Details of the experiment
-Minor rewording to the last paragraph.
3 Theoretical model
-Minor rewording in first and second paragraphs.
-Added remark regarding the validity of SPGPE even if spatial density vanishes in some regions.
-Corrected factor of sqrt(N) in the definition of the annihilation operator in footnote 1, to ensure canonical commutation relations are preserved.
-Added remark to the second-last paragraph of 3.5 regarding the (lack of) effect the perturbing barrier has on the thermal reservoir.
4 Results and Analysis
Minor changes to figure 5 - color palette changed to be colorblind-friendly, and legend added.
5 Discussion
Added discussion on the effect of atom losses at the end of 5.2.2.
Added comment on the inherent sensitivity to technical noise in red-detuned traps to the second paragraph in 5.3.

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