We report the observation of the scissors mode of a Bose-Einstein condensed gas of 87Rb atoms in a magnetic trap, which gives direct evidence of superfluidity in this system. The scissors mode of oscillation is excited by a sudden rotation of the anisotropic trapping potential. For a gas above T(c) (normal fluid) we detect the occurrence of oscillations at two frequencies, with the lower frequency corresponding to the rigid body value of the moment of inertia. Well below T(c) the condensate oscillates at a single frequency, without damping, as expected for a superfluid.
We have investigated the formation of vortices by rotating the purely magnetic potential confining a Bose-Einstein condensate. We modified the bias field of an axially symmetric TOP trap to create an elliptical potential that rotates in the radial plane. This enabled us to study the conditions for vortex nucleation over a wide range of eccentricities and rotation rates.
We report the experimental realisation of a versatile ring trap for ultracold
atoms. The ring geometry is created by the time-averaged adiabatic potential
resulting from the application of an oscillating magnetic bias field to a rf
dressed quadrupole trap. Lifetimes for a Bose-Einstein condensate in the ring
exceed 11s and the ring radius was continuously varied from 50$\mu$m to
261$\mu$m. An efficient method of loading the ring from a conventional TOP trap
is presented together with a rotation scheme which introduces angular momentum
into the system. The ring presents an opportunity to study the superfluid
properties of a condensate in a multiply connected geometry and also has
applications for matter-wave interferometry
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