Collisionless modes of a trapped Bose gas

TL;DR

This paper calculates the excitation frequencies of low-lying modes in a trapped Bose-condensed gas at finite temperatures, considering the dynamics of both condensed and noncondensed components, and compares results with experimental data.

Contribution

It introduces a comprehensive calculation including noncondensed cloud dynamics and explores mode coupling to external perturbations in trapped Bose gases.

Findings

Agreement with experimental results when both monopole modes are excited

Modes can strongly couple to external trapping potential perturbations

Both in-phase and out-of-phase monopole modes are relevant in experiments

Abstract

We calculate the excitation frequencies of the low-lying modes of a trapped Bose-condensed gas at nonzero temperatures. We include in our calculation the dynamics of the noncondensed cloud, and find agreement with experimental results if we assume that in the experiment both the in-phase and out-of-phase monopole modes are excited simultaneously. In order to explore whether this is indeed the correct explanation, we also calculate how strongly the modes couple to a perturbation of the external trapping potential.