Spin Relaxation in Single Layer and Bilayer Graphene

TL;DR

This study compares spin relaxation mechanisms in single-layer and bilayer graphene, revealing EY dominance in SLG and DP dominance in BLG due to differences in impurity effects and screening.

Contribution

It provides experimental evidence of contrasting spin relaxation behaviors in SLG and BLG, highlighting the role of screening and impurity effects.

Findings

SLG shows linear dependence of spin lifetime on momentum scattering time.

BLG exhibits inverse dependence, indicating different relaxation mechanisms.

Impurity effects are reduced in BLG, affecting spin relaxation.

Abstract

We investigate spin relaxation in graphene spin valves and observe strongly contrasting behavior for single layer graphene (SLG) and bilayer graphene (BLG). In SLG, the spin lifetime ({\tau}s) varies linearly with the momentum scattering time ({\tau}p) as carrier concentration is varied, indicating the dominance of Elliot-Yafet (EY) spin relaxation at low temperatures. In BLG, {\tau}s and {\tau}p exhibit an inverse dependence, which indicates the dominance of Dyakonov-Perel spin relaxation at low temperatures. The different behavior is due to enhanced screening and/or reduced surface sensitivity of BLG, which greatly reduces the impurity-induced EY spin relaxation.