Emergence of Turbulence in an Oscillating Bose-Einstein Condensate

Abstract

We report on the experimental observation of vortex tangles in an atomic Bose-Einstein condensate (BEC) of ;{87}Rb atoms when an external oscillatory perturbation is introduced in the trap. The vortex tangle configuration is a signature of the presence of a turbulent regime in the cloud. We also show that this turbulent cloud suppresses the aspect ratio inversion typically observed in quantum degenerate bosonic gases during free expansion. Instead, the cloud expands keeping the ratio between their axis constant. Turbulence in atomic superfluids may constitute an alternative system to investigate decay mechanisms as well as to test fundamental theoretical aspects in this field.

Realization of inverse Kibble–Zurek scenario with trapped Bose gases

“…Since no single rotation axis is imposed onto the system, the creation of vortices and anti-vortices is equally likely. The typical situation is that vortices and anti-vortices appear together in groups [27][28][29]. The vortex-antivortex pairs do not form bound dipoles, being not correlated with each other, except having opposite vorticities.…”

“…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].…”

“…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.…”

“…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…”