Spin and angular resolved photoemission experiments on epitaxial graphene

TL;DR

This study investigates spin polarization in epitaxial graphene on SiC(0001), revealing that observed signals are unlikely due to Rashba-type spin splitting, challenging previous interpretations and providing new insights into spin phenomena in graphene.

Contribution

The paper presents novel spin-resolved photoemission measurements on hydrogen intercalated graphene, showing that the observed spin polarization is not caused by Rashba-type splitting as previously thought.

Findings

Measured spin splitting of 0.024±0.005 Å⁻¹ in graphene.

Spin polarization signals are not due to Rashba-type effects.

Contradicts earlier reports of large Rashba splitting in graphene.

Abstract

Our recently reported spin and angular resolved photoemission (SARPES) results on an epitaxial graphene monolayer on SiC(0001) suggested the presence of a large Rashba-type spin splitting of \Delta k=(0.030+-0.005)1/A [1]. Although this value was orders of magnitude larger than predicted theoretically, it could be reconciled with the line width found in conventional spin-integrated high resolution angular resolved photoemission spectroscopy (ARPES) data. Here we present novel measurements for a hydrogen intercalated quasi free-standing graphene monolayer on SiC(0001) that reveal a spin polarization signal that - when interpreted in terms of the Rashba-Bychkov effect [2,3] - corresponds to a spin splitting of \Delta k=(0.024+-0.005)1/A. This splitting is significantly larger than the half width at half maximum of spin-integrated high resolution ARPES measurements which is a strong indication that the measured polarization signal does not originate from a Rashba-type spin splitting of the graphene pi-bands as we suggested in our previous report [1].