Out-of-phase oscillation between superfluid and thermal components for a trapped Bose condensate under oscillatory excitation

TL;DR

This paper reports the experimental observation of out-of-phase oscillations between superfluid and thermal components in a trapped Bose-Einstein condensate under oscillatory magnetic excitation, shedding light on vortex nucleation mechanisms.

Contribution

It introduces the observation of out-of-phase oscillation modes in a BEC under oscillatory magnetic fields, linking these dynamics to vortex formation processes.

Findings

Detected relative displacement between condensate and thermal cloud centers

Identified out-of-phase oscillation as a potential vortex nucleation mechanism

Observed ripples at the interface of condensed and thermal fractions

Abstract

The vortex nucleation and the emergence of quantum turbulence induced by oscillating magnetic fields, introduced by Henn E A L, et al. 2009 (Phys. Rev. A 79, 043619) and Henn E A L, et al. 2009 (Phys. Rev. Lett. 103, 045301), left a few open questions concerning the basic mechanisms causing those interesting phenomena. Here, we report the experimental observation of the slosh dynamics of a magnetically trapped $^{87}$Rb Bose-Einstein condensate (BEC) under the influence of a time-varying magnetic field. We observed a clear relative displacement in between the condensed and the thermal fraction center-of-mass. We have identified this relative counter move as an out-of-phase oscillation mode, which is able to produce ripples on the condensed/thermal fractions interface. The out-of-phase mode can be included as a possible mechanism involved in the vortex nucleation and further evolution when excited by time dependent magnetic fields.