Kármán vortex street in a two-component Bose–Einstein condensate

Vortex shedding from a moving obstacle potential in a two-component Bose–Einstein condensate is investigated numerically. For a miscible two-component condensate composed of ^23 Na and ^87 Rb atoms, in the wake of obstacle, the Kármán vortex street is discovered in one component, while the Kármán-like vortex street named ‘half-quantum vortex street’ is formed in another component. The other patterns of vortex shedding, such as the vortex dipoles, V-shaped vortex pairs and corresponding ‘half-quantum vortex shedding’, can also be found. The drag force acting on obstacle potential is calculated and discussed. The parameter region for various vortex patterns and critical velocity for vortex emission are presented. In addition, a ^85 Rb– ^87 Rb mixture is also considered, where the Kármán vortex street and other typical patterns exist in both components. Finally, we provide an experimental protocol for the above realization and observation.