Quantum Kármán vortex street in an immiscible two-component Bose–Einstein condensate
College of Physics and Electronic Engineering, Northwest Normal University, 730070, Lanzhou, People’s Republic of China
2 Laboratory of Atomic Molecular Physics and Functional Material, Northwest Normal University, 730070, Lanzhou, People’s Republic of China
3 Department of Basic Courses, Lanzhou Institute of Technology, 730050, Lanzhou, People’s Republic of China
Accepted: 21 October 2022
Published online: 3 November 2022
The dynamics of an immiscible two-component Bose–Einstein condensate (BEC) through a moving obstacle potential are numerically studied. It is found that the quantum Kármán vortex street consisting of quantized vortices and ghost vortices emerge after a moving Gaussian obstacle potential with appropriate parameters in an immiscible two-component BEC composed of two different hyperfine states of atoms. The vortex street is an observable quantized vortex in one component and an unobserved ghost vortex in another one. It is also obtained that vortex shedding contributes to the drag force by analyzing the instantaneous and time-averaged drag force acting on the obstacle potential. The phase diagrams of various vortex shedding patterns under different obstacle potential widths and moving velocities are derived by systematic numerical simulations. The quantum Kármán vortex street appears in a relatively narrow range, while other vortex patterns are more likely to appear, such as vortex dipoles, V-shaped vortex pairs, etc. Finally, the critical velocity curve for vortex emission and superfluid Reynolds number are discussed.
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