Josephson pi-state in a ferromagnetic insulator

TL;DR

This paper predicts atomic-scale 0-pi transitions in Josephson junctions with ferromagnetic insulator barriers, revealing that the ground state alternates with FI thickness and enabling stable pi-states in high-Tc superconductor junctions.

Contribution

It introduces the concept of atomic-scale 0-pi transitions in FI-based Josephson junctions and explains the phase-shift mechanism causing these transitions.

Findings

Ground state alternates between 0 and pi with FI thickness.

Phase-shifts depend on electron and hole wave numbers in FI.

Stable pi-state achievable with high-Tc superconductor junctions.

Abstract

We predict anomalous atomic-scale 0-pi transitions in a Josephson junction with a ferromagnetic-insulator (FI) barrier. The ground state of such junction alternates between 0- and pi-states when thickness of FI is increasing by a single atomic layer. We find that the mechanism of the 0-pi transition can be attributed to thickness-dependent phase-shifts between the wave numbers of electrons and holes in FI. Based on these results, we show that stable pi-state can be realized in junctions based on high-Tc superconductors with La$_2$BaCuO$_5$ barrier.