Experimental observation of spin-split energy dispersion in high-mobility single-layer graphene/WSe₂ heterostructures

We report the experimental determination of the band structure of single-layer graphene in the presence of strong proximity induced spin-orbit coupling. We achieve this in high-mobility hBN-encapsulated single-layer graphene and WSe₂ heterostructures by measurements of quantum oscillations. We observe clear spin-splitting of the graphene bands along with a substantial increase in the Fermi velocity. Using a theoretical model with realistic parameters to fit our experimental data, we uncover confirmation of a bandgap opening and band inversion in the single-layer graphene. Further, we establish that the deviation of the low-energy band structure from pristine single-layer graphene is determined primarily by the valley-Zeeman SOC and Rashba SOC, with the Kane-Mele SOC being inconsequential. Despite the robust theoretical predictions and observations of band-splitting, a quantitative measure of the spin splitting of the valence and the conduction bands and the consequent low-energy dispersion relation in single-layer graphene was lacking. Our combined experimental and theoretical study fills this lacuna.