Breaking the resilience of a two-dimensional Bose-Einstein condensate to   fragmentation
  A two-dimensional Bose-Einstein condensate (BEC) split by a radial potential barrier is investigated. We determine on an accurate many-body level the system's ground-state phase diagram as well as a time-dependent phase diagram of the splitting process. Whereas the ground state is condensed for a wide range of parameters, the time-dependent splitting process leads to substantial fragmentation. We demonstrate for the first time the dynamical fragmentation of a BEC despite its ground state being condensed. The results are analyzed by a mean-field model and suggest that a large manifold of low-lying fragmented excited states can significantly impact the dynamics of trapped two-dimensional BECs. 
Shachar Klaiman, Axel U. J. Lode, Alexej I. Streltsov, Lorenz S.   Cederbaum, and Ofir E. Alon
cond-mat.quant-gas quant-ph