Josephson Current Counterflow in Atomic Bose-Einstein Condensates

TL;DR

This paper investigates supercurrent counterflow in atomic Bose-Einstein condensates, demonstrating conditions for its observation in double-well traps with initial $\

Contribution

It introduces the concept of supercurrent counterflow in BECs and identifies conditions for its experimental realization in various trap geometries.

Findings

Counterflow effect observable in condensates with up to a few thousand atoms

Effect occurs in both attractive and repulsive condensates

Weak dependence on trap geometry

Abstract

Josephson weak links in superconductors can be engineered such that the phase difference across the junction is $\pi$ ($\pi$-junction),leading to the reversal of the current. The conditions under which the analogous effect of supercurrent counterflow can be achieved in a double-well atomic Bose-Einstein condensate are investigated. It is shown that this effect is observable for condensates up to a few thousand atoms, which are initially prepared in an anti-symmetric '$\pi$-state' and subsequently subjected to a uniformly increasing magnetic field gradient. This effect is found to be only weakly-dependent on trap geometry, and can be observed in both attractive and repulsive condensates.