Effect of Microwaves on the Current-Phase-Relation in SNS Josephson Junctions

TL;DR

This study explores how microwave irradiation influences the current-phase relation in SNS Josephson junctions, revealing that microwaves can suppress supercurrent near phase difference pi by exciting Andreev bound states, aligning with theoretical predictions.

Contribution

It demonstrates the impact of microwave irradiation on the CPR of SNS Josephson junctions, highlighting the excitation of Andreev bound states as a key mechanism.

Findings

Microwave irradiation can strongly suppress supercurrent near phase difference pi.

The shape of the CPR is significantly affected by microwave power.

The observed effects align with theoretical models of Andreev bound state excitation.

Abstract

We investigate the current-phase-relation (CPR) of long diffusive superconductor-normal metal-superconductor (SNS) Josephson junctions in thermodynamic equilibrium and under microwave irradiation. While in equilibrium good agreement with the predictions of quasi-classical theory is found, we observe that the shape of the CPR can be strongly affected by microwave irradiation. Close to a Josephson-phase difference of pi, the supercurrent can be strongly suppressed when increasing the rf-power. Our results can be understood in terms of microwave excitation of low-lying Andreev bound states across the mini-gap in the junction. In the frequency interval studied, this mechanism becomes important when the mini-gap closes at a phase difference of pi.