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Q: Quantenoptik und Photonik

Q 18: Quantengase II

Q 18.2: Talk

Tuesday, March 23, 2004, 11:15–11:30, HS 225

Fast rotating Bose-Einstein condensates in nonharmonic traps — •Sabine Stock, Vincent Bretin, Zoran Hadzibabic, and Jean Dalibard — Laboratoire Kastler Brossel, Département de Physique de l’ENS, 24 rue Lhomond, 75005 Paris, France

For rotating BECs in harmonic traps the rotation frequency is limited by the trap frequency, above which the centrifugal force overcomes the trapping force and the condensate‘s centre of mass is destabilized. From a quantum mechanical point of view the single particle ground state first becomes infinitely degenerate as the rotation frequency is increased, and then seizes to exist. In traps steeper than harmonic, this problem can be overcome so that the way to new regimes is opened.

In our experiment we produce condensates of 87Rb in a quadratic+quartic transverse potential, so that the quartic potential confines the condensate at all rotation frequencies. It was therefore possible to achieve a fast rotation regime where the vortex lattice becomes disordered and, for rotations faster than the trap frequency, completely No-dqdissolvesNo-dq.

These experiments represent a step towards regimes where a gas of ultra cold bosons is placed in a potential with a highly degenerate ground state. We plan to pursue this work towards regimes with much smaller numbers of atoms, where effects analogue to the Quantum Hall Effect might be observed.

[1] V. Bretin et al., cond-mat/0307464