Theory of Half Metal-Superconductor Heterostructures

TL;DR

This paper develops a theoretical framework to understand how spin rotation at superconductor/half-metal interfaces induces triplet correlations, enabling Josephson coupling in S/HM/S heterostructures.

Contribution

It introduces a new theory describing spin rotation-induced triplet correlations and their role in Josephson effects in superconductor/half-metal heterostructures.

Findings

Triplet correlations are induced by spin rotation at interfaces.

Surface spin-flip scattering enables Josephson coupling.

Physical properties of S/HM/S heterostructures are calculated.

Abstract

We investigate the coupling between two singlet superconductors separated by a half-metallic magnet. The mechanism behind the coupling is provided by the rotation of the quasiparticle spin in the superconductor during reflection events at the interface with the half metal. Spin rotation induces triplet correlations in the superconductor which, in the presence of surface spin-flip scattering, result in an indirect Josephson effect between the superconductors. We present a theory appropriate for studying this phenomenon and calculate physical properties for a superconductor/half metal/superconductor (S/HM/S) heterostructure.