Second sound dipole mode in a partially Bose-Einstein condensed gas

TL;DR

This paper investigates the second sound dipole mode in a partially Bose-Einstein condensed gas, analyzing its excitation, oscillation, and damping behavior across different conditions, and compares findings with theoretical Landau damping predictions.

Contribution

It provides experimental measurements of the second sound dipole mode's frequency and damping in a partially BEC, highlighting the effects of hydrodynamicity and temperature.

Findings

Damping rates agree with Landau damping near the collisionless regime

Damping increases with the hydrodynamicity of the gas

Oscillation frequency varies with trap confinement and temperature

Abstract

We study the second sound dipole mode in a partially Bose-Einstein condensed gas. This mode is excited by spatially separating and releasing the center-of-mass of the Bose-Einstein condensate (BEC) with respect to the thermal cloud, after which the equilibration is observed. The oscillation frequency and the damping rate of this mode is studied for different harmonic confinements and temperatures. The measured damping rates close to the collisionless regime are found to be in good agreement with Landau damping. For increasing hydrodynamicity of the cloud we observe an increase of the damping.