18 January 2006

Photo: AG Sengstock

After realizing quantum degeneracy, the experiment was consequently tuned to the high particle limit. In Bose-Einstein-condensates, it was observed that attractive interactions lead to an instability of the system, resulting in an implosion which is called 'mean-field-collapse'. In the ⁴⁰K-⁸⁷Rb-mixture, the interspecies interaction is attractive, but K and Rb itself repulse each other. We found a very clear feature of the collapse, a sudden localized atom loss in the center of the trap at the point of highest density and could observe even revivals. 3-body-losses were evaluated and a sudden increase at the onset of the collapse demonstrated. A detailed description is given in PRL96, 020401 (2006).