Spatio-temporal spin transport from first principles

TL;DR

This paper presents a first-principles computational framework using the Wigner function formalism to simulate quantum spin transport, including electron-phonon interactions, across various regimes and materials.

Contribution

It introduces a novel first-principles method for simulating spin transport that accounts for electron-phonon scattering and spin-orbit effects at device scales.

Findings

Identification of three regimes of incoherent spin transport: free induction decay, Dyakonov-Perel, and Elliott-Yafet.

Demonstration that spin diffusion length is insensitive to scattering strength in the Dyakonov-Perel regime.

Application to graphene under electric field showing the impact of electron-phonon scattering on spin transport.

Abstract

We introduce a computational framework for first-principles density matrix transport within the Wigner function formalism to predict transport of quantum-mechanical degrees of freedom such as spin over long time and length scales. This framework facilitates simulation of spin dynamics and transport from first principles, while accounting for electron-phonon scattering at device length scales. We demonstrate this framework to elucidate the impact of various spin-orbit field profiles, such as Rashba and persistent spin helix, on coherent spin transport in several materials. Using graphene under an electric field as an example to illustrate the impact of electron-phonon scattering on incoherent transport, we show how the transport changes with the strength of scattering. We identify three distinct regimes of incoherent spin transport corresponding to the free induction decay, Dyakonov-Perel and Elliott-Yafet regimes of spin relaxation. In particular, we show that the spin diffusion length is insensitive to the strength of scattering within the Dyakonov-Perel regime.