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 [1,2], left a few open questions concerning the basic mechanisms causing those interesting phenomema. 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-ofphase mode provides good evidences of a mechanism involved in the vortex nucleation and evolution when excited by time dependent magnetic fields.

Quantum turbulence in trapped atomic Bose–Einstein condensates

“…This approach is closely related to the proposal of M. Kobayashi and M. Tsubota [189] where rotations along distinct axes are combined to generate quantum turbulence in a trapped BEC. Another indicative for the emergence of turbulence is the observed counterflow between the thermal fluid and the superfluid [98], as already discussed in Sec. 5.3.…”

“…Last, more recently, there has been discussion on the possible introduction of a 'quantum' Reynolds number or a 'quantum' Navier-Stokes equation [65,98,99] to distinguish between laminar and turbulent superfluid helium flows and to characterize turbulence in a quantum gas. These are discussed in Sec.…”

“…The asymmetry in these density profiles as t hold increases reveals the relative motion between the two components. Source: paper of Tavares et al[98].…”

Nonlinear Dependence Observed in Quadrupolar Collective Excitation of a Trapped BEC

“…For small amplitudes, the CM is usually located near the center of the atomic density distribution, which is also the geometric center of the BEC. But, in some situations, at large perturbing amplitudes (> 80%), we observed slosh dynamics taking place, clearly displacing the thermal and condensed fractions in opposite, out-of-phase, CM motion 24 . It is important to mention that the dipolar mode preserves the AR when compared to an unperturbed BEC.…”

Investigations on momentum distributions and disorder in strongly out-of-equilibrium trapped Bose gases

“…In this thesis, we study three ways to quantify the non-equilibrium regimes produced by the action of a oscillatory excitation in Bose gases, with the same excitation protocol that was used in previous works. (39,(46)(47)(48)(49)(50) We focus on studies of momentum distribution, powerspectrum of fluctuations, and continuous entropy to probe non-equilibrium regimes in cigarshaped trapped gases in the searching of turbulence. The apparatus for performing these experiments prepares an ultracold quantum gas of some nano-Kelvins in a magnetic trap and applies a well controlled oscillatory magnetic excitation.…”