Spontaneous spin current due to triplet superconductor--ferromagnet interfaces

TL;DR

This paper investigates the emergence of a spontaneous bulk spin current at the interface between a triplet superconductor and a ferromagnet, revealing how it depends on various physical parameters and resembles Josephson charge currents.

Contribution

It introduces a theoretical framework for calculating the spin current using Andreev reflection coefficients in triplet superconductor-ferromagnet interfaces, highlighting the mechanisms behind its spontaneous appearance.

Findings

Spin current arises from spin-flip reflection of Cooper pairs.

The spin current's magnitude depends on magnetic orientation, exchange splitting, temperature, and pairing state.

The spin current exhibits similarities to Josephson charge currents.

Abstract

We examine the appearance of a spontaneous bulk spin current in a triplet superconductor in contact with a metallic ferromagnet. The spin current results from the spin-flip of Cooper pairs upon reflection from the interface with the ferromagnet, and is shown to display strong similarities to the spontaneous charge current in a Josephson junction. We express the spin current in terms of the Andreev reflection coefficients, which are derived by the construction of the quasiclassical scattering wavefunctions. The dependence of the spin current upon a number of parameters is investigated, in particular the orientation of the magnetic moment of the ferromagnet, the exchange splitting, the temperature, and the orbital pairing state of the triplet superconductor.