Solitonic Vortices in Bose-Einstein Condensates
  We analyse, theoretically and experimentally, the nature of solitonic vortices (SV) in an elongated Bose-Einstein condensate. In the experiment, such defects are created via the Kibble-Zurek mechanism, when the temperature of a gas of sodium atoms is quenched across the BEC transition, and are imaged after a free expansion of the condensate. By using the Gross-Pitaevskii equation, we calculate the in-trap density and phase distributions characterizing a SV in the crossover from an elongate quasi-1D to a bulk 3D regime. The simulations show that the free expansion strongly amplifies the key features of a SV and produces a remarkable twist of the solitonic plane due to the quantized vorticity associated with the defect. Good agreement is found between simulations and experiments. 
Marek Tylutki, Simone Donadello, Simone Serafini, Lev P. Pitaevskii,   Franco Dalfovo, Giacomo Lamporesi, and Gabriele Ferrari
cond-mat.quant-gas