Electron spin dynamics and electron spin resonance in graphene

TL;DR

This paper develops a theory of spin relaxation in graphene, identifying dominant intrinsic spin-orbit coupling and predicting longer spin coherence for spins perpendicular to the plane, with implications for spintronics.

Contribution

It presents a comprehensive theory including various spin-orbit couplings and compares theoretical and experimental spin relaxation data, highlighting the dominance of intrinsic coupling.

Findings

Intrinsic spin-orbit coupling dominates in graphene.

Spin coherence is longer for spins perpendicular to the plane.

Experimental conditions for bulk ESR in graphene are identified.

Abstract

A theory of spin relaxation in graphene including intrinsic, Bychkov-Rashba, and ripple spin-orbit coupling is presented. We find from spin relaxation data by Tombros et al. [Nature 448, 571 (2007).] that intrinsic spin-orbit coupling dominates over other contributions with a coupling constant of 3.7 meV. Although it is 1-3 orders of magnitude larger than those obtained from first principles, we show that comparable values are found for other honeycomb systems, MgB2 and LiC6; the latter is studied herein by electron spin resonance (ESR). We predict that spin coherence is longer preserved for spins perpendicular to the graphene plane, which is beneficial for spintronics. We identify experimental conditions when bulk ESR is realizable on graphene.