Periodic shedding of vortex dipoles from a moving penetrable obstacle in a Bose-Einstein condensate

TL;DR

This study explores how a moving penetrable obstacle in a Bose-Einstein condensate periodically sheds vortex dipoles, with shedding frequency increasing linearly with obstacle velocity, enabling controlled vortex generation.

Contribution

It demonstrates the periodic vortex dipole shedding from a penetrable obstacle and introduces a method for deterministic vortex dipole generation in BECs.

Findings

Vortex shedding frequency linearly depends on obstacle velocity.

Periodic vortex dipole shedding can be controlled via obstacle speed.

Method enables precise vortex dipole generation for experiments.

Abstract

We investigate vortex shedding from a moving penetrable obstacle in a highly oblate Bose-Einstein condensate. The penetrable obstacle is formed by a repulsive Gaussian laser beam that has the potential barrier height lower than the chemical potential of the condensate. The moving obstacle periodically generates vortex dipoles and the vortex shedding frequency $f_v$ linearly increases with the obstacle velocity $v$ as $f_v=a(v-v_c)$, where $v_c$ is a critical velocity. Based on periodic shedding behavior, we demonstrate deterministic generation of a single vortex dipole by applying a short linear sweep of a laser beam. This method will allow further controlled vortex experiments such as dipole-dipole collisions.