Theory of spin-orbit induced spin relaxation in functionalized graphene

TL;DR

This study compares spin relaxation mechanisms in hydrogenated and fluorinated graphene, revealing the dominant spin-orbit interactions and their effects on spin relaxation rates and anisotropy, using quantum simulations and Green's function calculations.

Contribution

It identifies the dominant spin-orbit coupling terms in functionalized graphene and demonstrates their impact on spin relaxation, providing a comparative analysis of hydrogen and fluorine adatoms.

Findings

PIA coupling dominates in hydrogenated graphene.

In fluorinated graphene, PIA and Rashba couplings interfere destructively.

Predicted deviation from 2:1 spin relaxation anisotropy.

Abstract

We perform a comparative study of the spin relaxation by spin-orbit coupling induced from adatoms (hydrogen and fluorine) in graphene. Two methods are applied, giving consistent results: a full quantum transport simulation of a graphene nanoribbon, and a T-matrix calculation using Green's functions for a single adatom in graphene. For hydrogenated graphene the dominant spin-orbit term for spin relaxation is PIA, the hitherto neglected interaction due to pseudospin inversion asymmetry. In contrast, in fluorinated graphene PIA and Rashba couplings destructively interfere, reducing the total spin relaxation rate. In this case we also predict a strong deviation from the expected 2:1 spin relaxation anisotropy for out- and in-plane spin orientations. Our findings should be useful to benchmark spin relaxation and weak localization experiments of functionalized graphene.