Spin correlation function theory of spin-charge conversion effects

TL;DR

This paper develops a correlation function-based theory for spin-charge conversion effects in spintronics, clarifying physical mechanisms and eliminating ambiguities related to spin current definitions.

Contribution

It introduces a novel theoretical framework using correlation functions to analyze spin-charge conversion effects, including spin Hall and spin pumping, in systems with spin-orbit interactions.

Findings

Provides a clear physical interpretation of spin-charge conversion.

Eliminates ambiguity in defining spin current.

Identifies spin current transmission efficiency as magnetic susceptibility.

Abstract

Theory of spin-charge conversion effects in spintronics are presented in terms of correlation functions of physical observables, spin and electric current. Direct and inverse spin Hall effects and spin pumping effect are studied considering metallic systems with random spin-orbit interaction and spatially nonuniform Rashba interaction. The theory is free from ambiguity associated with spin current, and provides clear physical picture of the spin-charge conversion effects. In the present approach, so-called the spin current transmission efficiency is essentially the nonuniform component of magnetic susceptibility.