Observable Vortex Properties in Finite Temperature Bose Gases

TL;DR

This paper investigates vortex dynamics in finite temperature Bose-Einstein condensates, revealing how decay rates, precession frequencies, and core brightness depend on temperature and thermal cloud interactions, with implications for experimental temperature measurement.

Contribution

It applies the ZNG formalism to analyze vortex behavior at finite temperatures, highlighting the nonlinear effects of condensate-thermal coupling on vortex properties.

Findings

Decay rate and precession frequency increase rapidly with temperature.

Thermal cloud density in vortex core is mostly independent of vortex position.

Core brightness can be used to estimate temperature experimentally.

Abstract

We study the dynamics of vortices in finite temperature atomic Bose-Einstein condensates, focussing on decay rates, precession frequencies and core brightness, motivated by a recent experiment (Freilich et al. Science 329, 1182 (2010)) in which real-time dynamics of a single vortex was observed. Using the ZNG formalism based on a dissipative Gross-Pitaevskii equation for the condensate coupled to a semi-classical Boltzmann equation for the thermal cloud, we find a rapid nonlinear increase of both the decay rate and precession frequency with increasing temperatures. The increase, which is dominated by the dynamical condensate-thermal coupling is also dependent on the intrinsic thermal cloud collisional dynamics; the precession frequency also varies with the initial radial coordinate. The integrated thermal cloud density in the vortex core is for the most part independent of the position of the vortex (except when it is near the condensate edge) with its value increasing with temperature. This could potentially be used as a variant to the method of Coddington et al. (Phys. Rev. A 70, 063607 (2004)) for experimentally determining the temperature.