Collapse suppression in Bose-Einstein condensate clouds with orbital angular momentum

In this work we explore, theoretically and numerically, the influence of the OAM on the dynamics and suppression of collapse of trapped matter waves with attractive interatomic interaction. We demonstrate that a radially-symmetric harmonic trap can support elliptically shaped rotating clouds of ultracold atoms which exhibit a collapse-free dynamically stable evolution with the number of particles greatly exceeding the threshold for radially-symmetric fundamental state of the trap. To achieve the suppression of collapse, one needs to increase ellipticity of the trapped state and its rotation (spiraling) velocity, by transferring orbital angular momentum to the matter wave, e.g. imprinting a twisted phase front onto an elliptic BEC cloud. As a result, the critical number of atoms for the collapse raises and the BEC cloud exhibits long-term dynamically stable behavior. The results of numerical simulations are in agreement with the modified collapse threshold for the elliptic BEC states with OAM, predicted by variational analysis.