Abstract
When a superfluid flows past an obstacle, quantized vortices can be created in the wake above a certain critical velocity. In the experiment by Kwon et al. [Phys. Rev. A 91, 053615 (2015)], the critical velocity was measured for atomic Bose-Einstein condensates (BECs) using a moving repulsive Gaussian potential, and was minimized when the potential height of the obstacle was close to the condensate chemical potential . Here we numerically investigate the evolution of the critical vortex shedding in a two-dimensional BEC with increasing and show that the minimum at the critical strength results from the local density reduction and vortex-pinning effect of the repulsive obstacle. The spatial distribution of the superflow around the moving obstacle just below is examined. The particle density at the tip of the obstacle decreases as increases to , and at the critical strength, a vortex dipole is suddenly formed and dragged by the moving obstacle, indicating the onset of vortex pinning. The minimum exhibits power-law scaling with the obstacle size as with .
- Received 9 October 2022
- Accepted 6 February 2023
DOI:https://doi.org/10.1103/PhysRevA.107.023310
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