Nucleation of quantized vortices in a gaseous Bose–Einstein condensate

Abstract

Using a focused laser beam we stir a Bose–Einstein condensate confined in a magnetic trap. When the stirring frequency lies near a critical value, compatible with the quadrupolar mode resonance, we observe the nucleation of a vortex even for a very small stirring anisotropy (of the order of 1%). The results presented here demonstrate that the nucleation of vortices in the case of a trapped BEC is driven by the resonant excitation of the rotating quadrupolar mode. Using a percussive excitation of the condensate, we measure the angular momentum of the condensate with the vortex, and we find that it is $\text{∼ℏ}$ per particle, as expected. For larger stirring frequencies, regular arrays of vortices are observed.