Graphene for spintronics: giant Rashba splitting due to hybridization with Au

TL;DR

This paper demonstrates that intercalating gold at the graphene-nickel interface induces a giant spin-orbit splitting in graphene, due to hybridization with gold's d-states, which could enable advanced spintronic devices.

Contribution

It reveals a significant proximity-induced spin-orbit coupling in graphene via Au intercalation, supported by experimental measurements and ab initio modeling.

Findings

Giant spin-orbit splitting (~100 meV) observed in graphene with Au intercalation.

Hybridization with Au-5d states causes the large spin-orbit effect.

Ab initio calculations show enhancement due to Au atoms closer to graphene.

Abstract

Graphene in spintronics has so far primarily meant spin current leads of high performance because the intrinsic spin-orbit coupling of its pi-electrons is very weak. If a large spin-orbit coupling could be created by a proximity effect, the material could also form active elements of a spintronic device such as the Das-Datta spin field-effect transistor, however, metal interfaces often compromise the band dispersion of massless Dirac fermions. Our measurements show that Au intercalation at the graphene-Ni interface creates a giant spin-orbit splitting (~100 meV) in the graphene Dirac cone up to the Fermi energy. Photoelectron spectroscopy reveals hybridization with Au-5d states as the source for the giant spin-orbit splitting. An ab initio model of the system shows a Rashba-split dispersion with the analytically predicted gapless band topology around the Dirac point of graphene and indicates that a sharp graphene-Au interface at equilibrium distance will account for only ~10 meV spin-orbit splitting. The ab initio calculations suggest an enhancement due to Au atoms that get closer to the graphene and do not violate the sublattice symmetry.