ac Josephson effect in the resonant tunneling through mesoscopic superconducting junctions

TL;DR

This paper explores how microwave irradiation influences the ac Josephson effect in mesoscopic superconducting junctions, revealing photon-assisted Andreev states that carry supercurrent and novel features on Shapiro steps.

Contribution

It introduces an analytical model for the ac Josephson effect considering photon-assisted Andreev states in mesoscopic superconducting junctions.

Findings

Photon-assisted Andreev states facilitate supercurrent transport.

Resonant levels near specific positions enhance dc components on Shapiro steps.

New features of the ac Josephson effect are revealed in the infinite gap limit.

Abstract

We investigate ac Josephson effect in the resonant tunneling through mesoscopic superconducting junctions. In the presence of microwave irradiation, we show that the trajectory of multiple Andreev reflections can be closed by emitting or absorbing photons. Consequently, photon-assisted Andreev states are formed and play the role of carrying supercurrent. On the Shapiro steps, dc component appears when the resonant level is near a series of positions with spacing of half of the microwave frequency. Analytical result is derived in the limit of infinite superconducting gap, based on which new features of ac Josephson effect are revealed.