Angular momentum in spin-phonon processes

TL;DR

This paper revises the quantum theory of spin relaxation by incorporating phonon spin, clarifying angular momentum transfer in elastic environments and providing insights into the Einstein-de Haas effect.

Contribution

It introduces the concept of phonon spin into the quantum theory of spin relaxation, enhancing understanding of angular momentum balance in elastic media.

Findings

Division of angular momentum into orbital and phonon spin parts is useful.

Analysis clarifies microscopic processes in the Einstein-de Haas effect.

Revises existing spin relaxation models with phonon spin concept.

Abstract

Quantum theory of spin relaxation in the elastic environment is revised with account of the concept of a phonon spin recently introduced by Zhang and Niu (PRL 2014). Similar to the case of the electromagnetic field, the division of the angular momentum associated with elastic deformations into the orbital part and the part due to phonon spins proves to be useful for the analysis of the balance of the angular momentum. Such analysis sheds important light on microscopic processes leading to the Einstein - de Haas effect.