Scattering theory of magnetic/superconducting junctions with spin active interfaces

TL;DR

This paper develops a generalized scattering theory for magnetic and superconducting heterostructures with spin-active interfaces, enabling analysis of spin-flip phenomena, conductance, and spin-torque effects in such systems.

Contribution

It introduces a four-component spinorial formalism based on Bogoliubov de Gennes theory to describe spin-flip processes in magnetic/superconducting junctions.

Findings

Quantum size effects influence conductance and spin-torque patterns.

Quantum beating patterns are observed in conductance and spin-torque.

The formalism accurately describes spin-flip phenomena in heterostructures.

Abstract

We formulate a generalized scattering field theory a la Buttiker describing particles transport in magnetic/superconducting heterostructures. The proposed formalism, characterized by a four- component spinorial wavefunction of the Bogoliubov de Gennes theory, allows to describe the spin flipping phenomena induced by noncollinear magnetizations in the scattering region. As a specific application of the theory, we analyze the conductance, the magnetoresistance and the generation of spin-torque produced by an applied voltage in a spin-valve system. Quantum size effects and quantum beating patterns both in the conductance and in the spin-torque are carefully described.