Nonadiabatic Josephson current pumping by microwave irradiation

TL;DR

This paper demonstrates how microwave irradiation can induce a controllable, nonadiabatic chiral Josephson current by breaking time-reversal and electron-hole symmetries, leading to a new type of Josephson transistor.

Contribution

It introduces a mechanism for nonadiabatic Josephson current pumping using microwave phase control and symmetry breaking, supported by theoretical models and Green's function analysis.

Findings

Microwave phase induces chirality in Cooper pair dynamics.

A controllable current-phase relation shift is achieved.

Chiral current changes sign near resonant transitions.

Abstract

Irradiating a Josephson junction with microwaves can operate not only on the amplitude but also on the phase of the Josephson current. This requires breaking time inversion symmetry, which is achieved by introducing a phase lapse between the microwave components acting on the two{\dag} sides of the junction. General symmetry arguments and the solution of a specific single level quantum dot model show that this induces chirality in the Cooper pair dynamics, due to the topology of the Andreev bound state wavefunction. Another essential condition is to break electron-hole symmetry within the junction. A shift of the current-phase relation is obtained, which is controllable in sign and amplitude with the microwave phase and an electrostatic gate, thus producing a "chiral" Josephson transistor. The dot model is solved in the infinite gap limit by Floquet theory and in the general case with Keldysh nonequilibrium Green's functions. The chiral current is nonadiabatic: it is extremal and changes sign close to resonant chiral transitions between the Andreev bound states.