MICROWAVE-INDUCED "SOMERSAULT EFFECT" IN FLOW OF JOSEPHSON CURRENT THROUGH A QUANTUM CONSTRICTION

TL;DR

This paper explores how microwave radiation influences supercurrent flow in mesoscopic Josephson junctions, revealing a novel 'Somersault effect' caused by photon-assisted transitions between Andreev bound states.

Contribution

It introduces the microwave-induced 'Somersault effect' in Josephson currents through quantum constrictions, highlighting the impact of electromagnetic fields on quantized electron modes.

Findings

Supercurrent can reverse direction under microwave irradiation.

Voltage spikes occur when the junction is current biased.

Discrete energy spectrum is key to the observed phenomena.

Abstract

We consider the supercurrent flow through gated mesoscopic semiconductor hetrostructures in which a two-dimensional normal constriction is confined between superconducting electrodes. We show that for these structures the Josephson current, carried by quantized electron modes, can be strongly affected by an electromagnetic field. Photon-assisted Landau-Zener transitions between Andreev bound states in the constriction manifest themselves in one of two ways: (i) If the phase difference between the superconducting elements is fixed a series of reversals in the direction of supercurrent flow occurs (Somersault effect). (ii) If instead the junction is current biased a series of voltage spikes is seen. Both manifestations are a direct consequence of the discrete energy spectrum of the mesoscopic junction. We discuss necessary conditions for the described phenomena to be experimentally observable.