Professor Christopher Foot

Abstract:

We theoretically investigate some of the observable properties of quasi-two-dimensional condensates. Using a variational model based on a Gaussian-parabolic trial wave function we calculate chemical potential, condensate size in time-of-flight, release energy, and collective excitation spectrum for varying trap geometries and atom numbers and find good agreement with recent published experimental results. © 2005 The American Physical Society.

Abstract:

We have measured the precession frequency of a vortex lattice in a Bose-Einstein condensate of Rb87 atoms. The observed mode corresponds to a collective motion in which all the vortices in the array are tilted by a small angle with respect to the z axis (the symmetry axis of the trapping potential) and synchronously rotate about this axis. This motion corresponds to excitation of a Kelvin wave along the core of each vortex and we have verified that it has the handedness expected for such helical waves, i.e., precession in the opposite sense to the rotational flow around the vortices.