Josephson Current Counterflow in Atomic Bose-Einstein Condensates

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Josephson weak links in superconductors can be engineered such that the phase difference across the junction is π (π-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 'π-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.