title: Vortex nucleation in a stirred Bose-Einstein condensate.
abstract: We studied the nucleation of vortices in a Bose-Einstein condensate stirred by a laser beam. The vortex cores were observed using time-of-flight absorption imaging. Depending on the stirrer size, either discrete resonances or a broad response was visible as the stir frequency was varied. Stirring beams small compared to the condensate size generated vortices below the critical rotation frequency for the nucleation of surface modes, suggesting a local mechanism of generation. In addition, we observed the centrifugal distortion of the condensate due to the rotating vortex lattice and found evidence for bent vortices.
authors.affiliation: Department of Physics, MIT-Harvard Center for Ultracold Atoms, MIT, Cambridge, Massachusetts 02139, USA. craman@gatech.edu
authors.forename: C
authors.initials: C
authors.lastname: Raman
authors.forename: J R
authors.initials: JR
authors.lastname: Abo-Shaeer
authors.forename: J M
authors.initials: JM
authors.lastname: Vogels
authors.forename: K
authors.initials: K
authors.lastname: Xu
authors.forename: W
authors.initials: W
authors.lastname: Ketterle