Microwave-Induced “Somersault Effect” in Flow of Josephson Current through a Quantum Constriction

We consider the supercurrent flow through gated mesoscopic semiconductor heterostructures in which a two-dimensional normal constriction is confined between superconducting electrodes. Photon-assisted Landau-Zener transitions between Andreev bound states in the constriction are shown to give rise to (i) a series of reversals in the direction of supercurrent flow (somersault effect) if the phase difference between the superconducting elements is fixed or (ii) a series of voltage spikes if the junction is current biased. We discuss necessary conditions for the described phenomena to be experimentally observable.