Impact of the impurity symmetry on orbital momentum relaxation and orbital Hall effect studied by the quantum Boltzmann equation

TL;DR

This paper develops a quantum Boltzmann equation approach to study how impurity symmetry affects orbital momentum relaxation and the orbital Hall effect, revealing different relaxation mechanisms and impurity influences.

Contribution

It introduces a microscopic impurity model into the quantum Boltzmann framework, elucidating the role of impurity symmetry in orbital transport phenomena.

Findings

Axial symmetry impurities lead to Dyakonov-Perel relaxation.

Broken symmetry impurities cause rapid Elliott-Yafet relaxation.

Impurity details influence the intrinsic and skew-scattering orbital Hall effects.

Abstract

We develop a quantum Boltzman equation approach that incorporates microscopic impurity models into the theory of orbital transport, revealing, how impurity properties, including their symmetry, influence the relaxation of orbital momentum and the orbital Hall effect. Specifically, we demonstrate that when the impurity potential has axial symmetry, the relaxation is governed by the Dyakonov-Perel mechanism. In contrast, when this symmetry is broken, scattering can result in a rapid Elliot-Yafet relaxation of orbital momentum. The details of impurity potential also affect the intrinsic orbital Hall effect even when the impurity concentration is very small. Impurities that alter the orbital texture can also give rise to a skew-scattering contribution to the orbital Hall effect, although this does not necessarily dominate in materials that are nearly pristine due to the Dyakonov-Perel relaxation.