Transverse modes of a cigar-shaped Bose-Einstein condensate

TL;DR

This paper investigates the transverse collective modes of a highly elongated Bose-Einstein condensate, revealing unique features like insensitivity of mode frequency to interactions and explaining low damping rates through finite temperature simulations.

Contribution

It provides a detailed analysis of transverse modes in cigar-shaped BECs, highlighting their temperature-dependent behavior and explaining experimental observations of damping rates.

Findings

Mode frequency is insensitive to interaction strength.

Damping rates are very small and match experimental data.

Small damping is specific to the transverse breathing mode in elongated traps.

Abstract

We discuss the collective modes in a harmonically trapped, highly-elongated Bose condensed gas. The transverse breathing mode exhibits a number of interesting features, such as the insensitivity of the condensate mode frequency to the interaction strength, and the closeness of the frequency to that of the non-condensed thermal cloud in the collisionless limit. Using finite temperature simulations, we show that these features are responsible for the very small damping rate observed experimentally. Our results for the temperature dependence of the damping rate and frequency shift are in excellent agreement with experiment. We also demonstrate that the unusually small damping rate does not arise for the $m=2$ mode or for more isotropic trap potentials, suggesting further possible experimental tests of our theory.