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

Abstract

The vortex nucleation and the emergence of quantum turbulence induced by oscillating magnetic fields, introduced by Henn et al (2009 Phys. Rev. A 79 043619) and Henn et al (2009 Phys. Rev. Lett. 103 045301), left a few open questions concerning the basic mechanisms causing these interesting phenomena. Here, we report the experimental observation of the slosh dynamics of a magnetically trapped 87Rb Bose–Einstein condensate (BEC) under the influence of a time-varying magnetic field. We observed a clear relative displacement between the condensed and 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 fraction boundary region. The out-of-phase mode, induced by time-dependent magnetic fields, is likely to be an additional mechanism to the vortex nucleation.