On instabilities of filled vortex in a two-component Bose-Einstein condensate

A binary Bose-Einstein condensate of cold atoms, with sufficiently strong intercomponent repulsion resulting in spatial segregation, is investigated numerically. Configurations as a multiple quantum vortex in one component are considered, with vortex core filled by the other component. An efficient radius of the core may exceed the width of the transient layer between the components, and then an analogy with a filled cylindrical vortex in classical hydrodynamics of two immiscible perfect fluids takes place. The analogy allows us to analyze for the condensate filled vortex the longitudinal "sausage" instability, and the transverse instability caused by the "tangent shock", as well as a stable regime in the parametric gap between the instabilities. Long-lived coherent structures appearing in some cases on the nonlinear stages of both instabilities are observed numerically.