Splitting of singly and doubly quantized composite vortices in two-component Bose-Einstein condensates

Pekko Kuopanportti; Soumik Bandyopadhyay; Arko Roy; D. Angom

doi:10.1103/PhysRevA.100.033615

paper

Splitting of singly and doubly quantized composite vortices in two-component Bose-Einstein condensates

arXiv:1808.08223 · doi:10.1103/PhysRevA.100.033615

Abstract

We study numerically the dynamical instabilities and splitting of singly and doubly quantized composite vortices in two-component Bose-Einstein condensates harmonically confined to quasi two dimensions. In this system, the vortices become pointlike composite defects that can be classified in terms of an integer pair $(κ_{1}, κ_{2})$ of phase winding numbers. Our simulations based on zero-temperature mean-field theory reveal several vortex splitting behaviors that stem from the multicomponent nature of the system and do not have direct counterparts in single-component condensates. By calculating the Bogoliubov excitations of stationary axisymmetric composite vortices, we find nonreal excitation frequencies (dynamical instabilities) for the singly quantized $(1, 1)$ and $(1, - 1)$ vortices and for all variants of doubly quantized vortices, which we define by the condition $max_{j = 1, 2} ∣ κ_{j} ∣ = 2$ . While the short-time predictions of the linear Bogoliubov analysis are confirmed by direct time integration of the Gross-Pitaevskii equations of motion, the time integration also reveals intricate long-time decay behavior not captured by the linearized dynamics. First, the $(1, \pm 1)$ vortex is found to be unstable against splitting into a $(1, 0)$ vortex and a $(0, \pm 1)$ vortex. Second, the $(2, 1)$ vortex exhibits a two-step decay process in which its initial splitting into a $(2, 0)$ vortex and a $(0, 1)$ vortex is followed by the off-axis splitting of the $(2, 0)$ vortex into two $(1, 0)$ vortices. Third, the $(2, - 2)$ vortex is observed to split into a $(- 1, 1)$ vortex, three $(1, 0)$ vortices, and three $(0, - 1)$ vortices. Each of these splitting processes is the dominant decay mechanism of the respective stationary composite vortex for a wide range of intercomponent interaction strengths and relative populations of the two condensate components and should be amenable to experimental detection.

arXiv comment17 pages, 20 color figures; v2 is identical in content to the published article

Splitting of singly and doubly quantized composite vortices in two-component Bose-Einstein condensates

Abstract

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