We study experimentally and theoretically a cold trapped Bose gas under critical rotation, i.e., with a rotation frequency close to the frequency of the radial confinement. We identify two regimes: the regime of explosion where the cloud expands to infinity in one direction, and the regime where the condensate spirals out of the trap as a rigid body. The former is realized for a dilute cloud, and the latter for a condensate with the interparticle interaction exceeding a critical value. This constitutes a novel system in which repulsive interactions help in maintaining particles together.

Phys. Rev. Lett.

Rosenbusch, P, Petrov, D. S, Sinha, S, Chevy, F, Bretin, V, Castin, Y, … Dalibard, J. (2002). Critical rotation of a harmonically trapped Bose gas. Phys.Rev.Lett., 88(Article number: 250403), 1–4.