\pi states in all-pnictide Josephson junctions

TL;DR

This paper investigates the Josephson effect in all-pnictide junctions with $s_{ ext{±}}$ superconductors, predicting phenomena like high-temperature $ ext{π}$ states and temperature-induced $ ext{π} ightarrow 0$ crossovers based on band ratios.

Contribution

It derives an equation for Andreev bound states in $s_{ ext{±}}/I/s_{ ext{±}}$ junctions and predicts novel Josephson current behaviors influenced by band ratio and temperature.

Findings

Prediction of high-temperature $ ext{π}$ states.

Observation of $ ext{π} ightarrow 0$ crossover with decreasing temperature.

Dependence of Josephson current features on band ratio and barrier strength.

Abstract

We study the Josephson effect in $s_{\pm}/I/s_{\pm}$ junctions made by two bands reversed sign s-wave ($s_{\pm}$) superconductive materials. We derive an equation providing the bound Andreev energy states parameterized by the band ratio $\alpha$, a parameter accounting for the weight of the second band with respect to the first one at the interface. For selected values of the band ratio and tunnel barrier amplitude, we predict various features of the Josephson current, among which a possible high temperature $\pi$ state of the junction (a doubly degenerate junction ground state) and a $\pi \rightarrow 0$ crossover with decreasing temperature.