Vortex excitations in binary mixture of trapped Bose-Einstein condensates

Elementary excitations of vortices placed in one component of a binary mixture of Bose-Einstein condensates have been studied using perturbative and numerical solutions of the linearised equations for excitations, and numerical simulation of the coupled Gross-Pitaevskii equations. Two distinct instabilities originating from resonances of the excitations have been found. One leads to the vortex drift out of the condensate. The second is the splitting of the higher order vortices into unit ones. The drift instability in particular originates from the extra, compared to the case of the single-component condensate, degeneracy of the vortex spectrum in the limit of the non-interacting gas. The stabilizing role played by the vortex free component of the condensate is revealed and several distinct scenarios of the splitting resulting in different dynamics of the unit vortices are described. ∗URL: www://http.cnqo.strath.ac.uk/∼dmitry