Superfluid-to-solid crossover in a rotating Bose-Einstein condensate - art.no. 190401

The properties of a rotating Bose-Einstein condensate confined in a prolate cylindrically symmetric trap are explored both analytically and numericall y. As the rotation frequency increases, an ever greater number of vortices are energetically favored. Though the cloud anisotropy and moment of inerti a approach those of a classical fluid at high frequencies, the observed vor tex density is consistently lower than the solid-body estimate. Furthermore , the vortices are found to arrange themselves in highly regular triangular arrays, with Little distortion even near the condensate surface. These res ults are shown to be a direct consequence of the inhomogeneous confining po tential.