Microwave-induced 'Somersault effect' in the flow of Josephson current through a quantum constriction

We consider the supercurrent flow through a gated two-dimensional normal constriction confined between superconducting electrodes. Photon-assisted Landau-Zener transitions between Andreev bound states in the constriction are shown to give rise to a series of reversals in the direction of supercurrent flow.