Watching dark solitons decay into vortex rings in a Bose-Einstein   condensate
  We have created spatial dark solitons in two-component Bose-Einstein condensates in which the soliton exists in one of the condensate components and the soliton nodal plane is filled with the second component. The filled solitons are stable for hundreds of milliseconds. The filling can be selectively removed, making the soliton more susceptible to dynamical instabilities. For a condensate in a spherically symmetric potential, these instabilities cause the dark soliton to decay into stable vortex rings. We have imaged the resulting vortex rings. 
B. P. Anderson, P. C. Haljan, C. A. Regal, D. L. Feder, L. A. Collins,   C. W. Clark, and E. A. Cornell