Excitation of Kármán vortex street in Bose–Einstein condensate with moiré lattice

The excitation of various wake patterns in a Bose–Einstein condensate (BEC) with moiré lattice is investigated numerically. The effects of physical parameters such as the velocity of the obstacle potential and the depth of the moiré lattice on vortex shedding are systematically investigated using numerical simulation. Appropriate parameters lead to the shedding of periodic vortex pairs and the formation of different wake patterns. Interestingly, when the vortex is situated at the potential well, its size is smaller than at the potential barrier of moiré lattice, indicating that its size is reduced in the higher-density region. The formation of Kármán vortex street (Kvs) becomes less favorable as the moiré lattice deepens. We also find that if a single vortex is shed behind the obstacle potential, the wake pattern eventually exhibits Kvs. It is worth noting that the distance between a pair of vortices and the angular frequency of their rotation oscillates periodically with time evolution. Additionally, as more vortices are shed from the obstacle potential, the kinetic energy, interaction energy and total energy in the system increase, and the potential energy exhibits oscillatory behavior. The direction of motion of the obstacle potential in the moiré lattice affects the vortex distribution. Furthermore, we propose a possible implementation of the Kvs in a BEC with moiré lattice.