Recently it became possible to create Bose-Einstein Condensates (BEC) of ultracold atomic gases in close vicinity of cryogenically cooled solid state surfaces. On one hand this opens the possibility to manipulate BECs by electronic elements at the solid state surface (so called "Atom-Chips") and do experiments with them. On the other hand the Bose-Einstein Condensate is a highly sensitive probe that can be used to measure the surface of the solid. We are presently studying the interaction of BECs with superconducting surfaces in collaboration with J. Fortagh and D. Kölle at the University of Tübingen.
Oscillations of a dipolar BEC (see picture) create eddy currents in a nearby superconductor via the time dependent magnetic field. The eddy currents in turn affect the motion of the BEC, like its oscillation frequency and its collective modes. This effect is larger than the effect of the Casimir-Polder force and should be measurable for Cr-52 atoms [1]. Our theoretical calculations also show that the eddy current effect has a specific dependence on the number of atoms in the condensate, which can be used as an experimental fingerprint for the observation of this effect and a distinction from the Casimir-Polder force. The eddy current effect produces a certain type of anharmonicity for the BEC. This anharmonicity can lead to a coupling of the center-of-mass oscillation of the BEC to its collective modes, which we have studied in Ref. [2].