Superflow in a toroidal Bose-Einstein condensate: an atom circuit with a tunable weak link

TL;DR

This paper reports the creation of a long-lived persistent current in a toroidal Bose-Einstein condensate with a tunable weak link, demonstrating superflow behavior and critical velocity related to vortex pair creation, marking the first realization of a closed-loop atom circuit.

Contribution

It introduces the first realization of an elementary closed-loop atom circuit with a tunable weak link in a Bose-Einstein condensate.

Findings

Persistent current lasts ~40 seconds.

Superflow stops when local velocity exceeds critical velocity.

Critical velocity matches vortex-antivortex pair creation theory.

Abstract

We have created a long-lived (~ 40 s) persistent current in a toroidal Bose-Einstein condensate held in an all-optical trap. A repulsive optical barrier creates a tunable weak link in the condensate circuit, which can affect the current around the loop. Superflow stops abruptly at a barrier strength such that the local flow velocity exceeds a critical velocity. The measured critical velocity is consistent with dissipation due to the creation of vortex-antivortex pairs. This system is the first realization of an elementary closed-loop atom circuit.