Emergence of Turbulence in an Oscillating Bose-Einstein Condensate

We report on the experimental observation of vortex tangles in an atomic Bose-Einstein condensate (BEC) of ${}^{87}\mathrm{Rb}$ 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.

Figure 1

(a) Experimental configuration to nucleate vortices in the BEC, showing the anti-Helmholtz coils slightly misaligned from the condensate long axis, and (b) pictorial view of the expected movements or deformations suffered by the condensate cloud.

Figure 2

(a) Atomic optical density after 15 ms of free expansion showing vortex structures spread all around the cloud resembling the vortex tangle regime proposed in Ref. 8, and (b) schematic diagram showing the inferred distribution of vortices as obtained from image shown in (a).

Figure 3

(a) Comparison between the free expansion of a normal BEC showing the well-known aspect ratio inversion (left) and a turbulent cloud (right) that keeps its aspect ratio while expanding. (b) Quantitative plot of the aspect ratios of the normal BEC cloud (circles) and the quantum turbulent cloud (squares). The lines are only a guide for the eye to stress the observed behavior.