Enhanced Rashba and exchange effects in bridge-structure graphene on Ni(111) from DFT with spin-orbit coupling calculations

A considerably enhanced Rashba coefficient, $\alpha$ of up to ∼1.7 $eV\AA$ in single layer graphene (SLG) on Ni(111) in bridge-top (BT) configuration is obtained using density functional theory with spin-orbit coupling calculations. This is attributed to significant proximity and exchange effects in the BT configuration of SLG/Ni arising from a direct and enhanced Ni-$d_{z^2}$ interaction with SLG-$\pi$ states. The Rashba and exchange splitting occur in the graphene bands directly above and below the E_F in the dispersion along the $M-K-M^{\prime }$ path, that is involving the Dirac point. No Rashba splitting is noted along $\Gamma -M$ direction in agreement with angle-resolved photoemission spectroscopy (ARPES). The above results reveal the specific conformation of SLG on ferromagnetic substrate different from the commonly studied top-fcc (TF) structure and paves the way for SLG for spin-orbitronics without the need for interfacing or intercalating heavy and precious metals.