MIT Group Stirs the BEC

In a recent article in Physical Review Letters, Wolfgang Ketterle's group describes how they studied the nucleation of vortices in a Bose-Einstein condensate stirred by a laser beam. They were able to see the vortex cores by using time-of-flight absorption imaging. Either a discrete resonance or a broad response of the condensate was visible as the stir frequency was varied, depending on the size of the stirring beam. Because stirring beams small compared to the condensate size generated vortices below the critical rotation frequency for the nucleation of surface modes, a local mechanism of vortex generation is suggested. The group also observed centrifugal distortion of the condensate due to the rotating vortex lattice and found evidence for bent vortices.

The article "Vortex Nucleation in a Stirred Bose-Einstein Condensate" by C. Raman, J. R. Abo-Shaeer, J. M. Vogels, K. Xu, and W. Ketterle (Phys. Rev. Lett. 87, 210402 (2001)) is available here.