Supersonic flow of a Bose-Einstein condensate past an oscillating attractive-repulsive obstacle

TL;DR

This paper uses numerical simulations to study how a Bose-Einstein condensate reacts to an oscillating obstacle, revealing different vortex patterns and drag behaviors depending on oscillation frequency.

Contribution

It provides new insights into vortex formation and drag force behavior in BECs under oscillating obstacles, including modeling of ship waves and excitation suppression at high frequencies.

Findings

Vortex dipoles emitted at slow oscillations

Lined up vortex dipoles at moderate oscillations

Negative drag force at high frequencies

Abstract

We investigate by numerical simulations the pattern formation after an oscillating attractive-repulsive obstacle inserted into the flow of a Bose-Einstein condensate. For slow oscillations we observe a complex emission of vortex dipoles. For moderate oscillations organized lined up vortex dipoles are emitted. For high frequencies no dipoles are observed but only lined up dark fragments. The results shows that the drag force turns negative for sufficiently high frequency. We also successfully model the {\it ship waves} in front of the obstacle. In the limit of very fast oscillations all the excitations of the system tend to vanish.