Switching the sign of Josephson current through Aharonov-Bohm interferometry

TL;DR

This paper demonstrates how to control the sign and magnitude of the Josephson supercurrent in a superconductor-normal metal-superconductor junction using Aharonov-Bohm interferometry, enabling a tunable $$-junction.

Contribution

It introduces a method to realize a fully controllable $$-junction via electro-magnetostatic Aharonov-Bohm effect in a ballistic ring, with practical implementation considerations.

Findings

The supercurrent sign can be switched by magnetic flux and gate voltage.

A fully controllable $$-junction is achievable.

The proposed setup is feasible in realistic experimental conditions.

Abstract

We investigate the DC Josephson effect in a superconductor-normal metal-superconductor junction where the normal region consists of a ballistic ring. We show that a fully controllable $\pi$-junction can be realized through the electro-magnetostatic Aharonov-Bohm effect in the ring. The sign and the magnitude of the supercurrent can be tuned by varying the magnetic flux and the gate voltage applied to one arm, around suitable values. The implementation in a realistic set-up is discussed.