Properties of vortices in Bose-Einstein condensates

One of the key issues related to superfluidity is the existence of quantized vortices. Following recent experiments on Bose-Einstein condensates exhibiting vortices, we investigate the behavior of the wave function which solves the Gross-Pitaevskii equation. For a rotating Bose-Einstein condensate in a harmonic trap, we give a simplified expression of the Gross-Pitaevskii energy in the Thomas-Fermi regime, which only depends on the number and shape of the vortex lines. This allows us to study in detail the structure of the line of a single quantized vortex, which has a U or S shape. S type vortices exist for all values of the angular velocity Omega but are not minimizers of the energy while U vortices are minimizers and exist only for Omega sufficiently large, Finally, we study the drag created by the movement of a detuned laser beam in a condensate and the nucleation of vortices in the low density region close to the boundary layer of the cloud. (C) 2004 Academie des sciences. Published by Elsevier SAS. All rights reserved.