Collapse and Bose - Einstein condensation in a trapped Bose gas with negative scattering length

We find that the key features of the evolution and collapse of a trapped Bose condensate with negative scattering length are predetermined by the particle flux from the non-equilibrium above-condensate cloud to the condensate and by 3-body recombination of Bose-condensed atoms. The collapse, starting once the number of Bose-condensed atoms N 0 reaches the critical value, ceases and turns to expansion when the density of the collapsing cloud becomes so high that the recombination losses dominate over attractive interparticle interaction. As a result, we obtain a sequence of collapses, each of them followed by dynamic oscillations of the condensate. In every collapse the 3-body recombination burns only a part of the Bose-condensed atoms, and N 0 always remains finite. However, it can comparatively slowly decrease after the collapse, due to the transfer of the condensate paqrticles to the above-condensate cloud in the course of damping of the condensate oscillations. After the discovery of Bose-Einstein condensation (BEC) in trapped clouds of alkali atoms [1–3], one of the central questions in the field of Bose-condensed gases concerns the influence of interparticle interaction on the character of BEC. In this respect the Rice experiments with 7 Li [2,4] attract a special interest, since a weakly interacting gas (n|a| 3 ≪ 1,