Theory of quantum transport in Josephson junctions with a ferromagnetic insulator

TL;DR

This paper models quantum transport in Josephson junctions with ferromagnetic insulators, revealing atomic-scale 0-pi oscillations and stable pi-states, which could be useful for quantum computing architectures.

Contribution

It explicitly considers the band structure of ferromagnetic insulators and demonstrates atomic-scale oscillations and stable pi-states in Josephson junctions.

Findings

Formation of pi-junction in FI-based systems

Atomic-scale 0-pi oscillation with single atomic layer period

Stable pi-state achievable with high-Tc superconductor junctions

Abstract

We investigate the Josephson transport through ferromagnetic insulators (FIs) by taking into account the band structure of FIs explicitly. Using the recursive Green's function method, we found the formation of a pi-junction in such systems. Moreover the atomic-scale 0-pi oscillation is induced by increasing the thickness of FI and its oscillation period is universal, i.e., just single atomic layer. 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. Such FI-based Josephson junctions may become an element in the architecture of future quantum computers.