Surface excitations, shape deformation and the long-time behavior in a stirred Bose-Einstein condensate

The surface excitations, shape deformation and the formation of persistent current for a Gaussian obstacle potential rotating in an highly oblate Bose-Einstein condensate(BEC)are investigated. Vortex dipole can be produced and trapped in the center of the stirrer even for slow motion of the stirring beam. When the barrier angular velocity is above some critical value, the condensate shape can be deformed remarkably according to the rotation frequency due to the existence of plenty of surface wave excitations. After a long enough time, a few vortices are found to be left either trapped in the condensate or pinned by the obstacle, a vortex dipole or several vortices can be trapped at the beam center, which enables the possibility of vortex manipulation.