Route to turbulence in a trapped Bose-Einstein condensate

Abstract

We have studied a Bose-Einstein condensate of 87 Rb atoms under an oscillatory excitation. For a fixed frequency of excitation, we have explored how the values of amplitude and time of excitation must be combined in order to produce quantum turbulence in the condensate. Depending on the combination of these parameters different behaviors are observed in the sample. For the lowest values of time and amplitude of excitation, we observe a bending of the main axis of the cloud. Increasing the amplitude of excitation we observe an increasing number of vortices. The vortex state can evolve into the turbulent regime if the parameters of excitation are driven up to a certain set of combinations. If the value of the parameters of these combinations is exceeded, all vorticity disappears and the condensate enters into a different regime which we have identified as the granular phase. Our results are summarized in a diagram of amplitude versus time of excitation in which the different structures can be identified. We also present numerical simulations of the Gross-Pitaevskii equation which support our observations.

Realization of inverse Kibble–Zurek scenario with trapped Bose gases

“…In the time-of-flight observation, the turbulent atomic cloud expands isotropically [27][28][29]. This suggests that the observed random vortex turbulence is a kind of Vinen turbulence [38,39].…”

“…We employ the same experimental setup as in the experiments studying quantum turbulence of trapped 87 Rb atoms [27][28][29]. The gas of 87 Rb atoms is cooled down to the state where almost all atoms, up to 70% are condensed, with the number of atoms in Bose-Einstein condensate being N ≈ 2 × 10 5 .…”

“…After forming equilibrium Bose-Einstein condensate, the atomic cloud is subject to an oscillatory trap modulation that shakes the condensate without imposing a rotation axis, but preserving the cloud isotropy [30]. As in our previous papers [27][28][29], we use the perturbing potential…”

“…This perturbing potential distorts the atomic cloud with a combination of deformations, rotations, and displacements [27][28][29]. The modulation amplitude and time can be varied in a wide range, thus, varying the energy injected into the system.…”

“…In the typical time-of-flight procedure, the chaotization [34] and nonadiabatic [35] effects do not occur and the expanding atomic cloud preserves the features of the state inside the trap [27][28][29].…”