The 0 and the pi phase Josephson coupling through an insulating barrier with magnetic impurities

TL;DR

This study investigates Nb-FeSi-Nb Josephson junctions with magnetic impurities, revealing coexisting 0 and π states within a single junction, leading to a distinctive cusp in the critical current's temperature dependence.

Contribution

It demonstrates the coexistence of 0 and π states in a single insulating barrier Josephson junction with magnetic impurities, a novel observation in such systems.

Findings

Coexistence of 0 and π states within one junction.

Sharp cusp in critical current temperature dependence.

Different temperature dependencies of supercurrents cause the cusp.

Abstract

We have studied temperature and field dependencies of the critical current $I_{C}$ in the Nb-Fe$_{0.1}$Si$_{0.9}$-Nb Josephson junction with tunneling barrier formed by paramagnetic insulator. We demonstrate that in these junctions the co-existence of both the 0 and the $\pi$ states within one tunnel junction takes place which leads to the appearance of a sharp cusp in the temperature dependence $I_{C}(T)$ similar to the $I_{C}(T)$ cusp found for the $0-\pi$ transition in metallic $\pi$ junctions. This cusp is not related to the $0-\pi$ temperature induced transition itself, but is caused by the different temperature dependencies of the opposing 0 and $\pi$ supercurrents through the barrier.