Characterizing the momentum distribution of vortex systems in an expanded Bose-Einstein condensate

The quantization of the vorticity and the ease of experimental accessibility and control make Bose-Einstein condensates ideal systems to study the dynamics of disordered arrangements of vortices, or vortex tangles. Recently, the experimental generation of a vortex tangle in a cigar shaped BEC [1] has revealed that upon expansion the condensate maintains its aspect ratio, in contrast to the well-established inversion of aspect ratio for an elongated non-turbulent BEC. We investigate the requirements for this self similar expansion by numerically modelling the expansion of a BEC with various vortex configurations, including vortex lattices, array of vortex dipoles and vortex tangles. Furthermore, we calculate the momentum distribution [2] of these condensates, both before and during the expansion, with the aim to determine whether this quantity characterizes the vortex configuration in a reliable way.\\[4pt] [1] Henn et al. PRL 103, 045301 (2009).\\[0pt] [2] Thompson et al. Laser Phys. Lett. 11, 015501 (2014).