A unified theory of spin-relaxation due to spin-orbit coupling in metals and semiconductors

TL;DR

This paper develops a unified theoretical framework for understanding spin-relaxation mechanisms in metals and semiconductors caused by spin-orbit coupling, bridging the gap between previously separate models.

Contribution

It unifies the Elliott-Yafet and Dyakonov-Perel theories into a single model applicable to generic two-band systems, revealing crossover regimes between the two mechanisms.

Findings

Recovery of known limiting cases of spin-relaxation

Identification of parameter domains for crossover between mechanisms

Linking inversion symmetry states to spin-relaxation behavior

Abstract

Spintronics is an emerging paradigm with the aim to replace conventional electronics by using electron spins as information carriers. Its utility relies on the magnitude of the spin-relaxation, which is dominated by spin- orbit coupling (SOC). Yet, SOC induced spin-relaxation in metals and semiconductors is discussed for the seemingly orthogonal cases when inversion symmetry is retained or broken by the so-called Elliott-Yafet and Dyakonov-Perel spin-relaxation mechanisms, respectively. We unify the two theories on general grounds for a generic two-band system containing intra- and inter-band SOC. While the previously known limiting cases are recovered, we also identify parameter domains when a crossover occurs between them, i.e. when an inversion symmetry broken state evolves from a Dyakonov-Perel to an Elliott-Yafet type of spin-relaxation and conversely for a state with inversional symmetry. This provides an ultimate link between the two mechanisms of spin-relaxation.