LAUSR

We study the energy dispersion relation of the $\ensuremath{\pi}$ and ${\ensuremath{\pi}}^{*}$ bands in epitaxial monolayer graphene on a semi-infinite Ir(111) substrate by a first-principles density-functional calculation. For this purpose, we employ a realistic surface structure in which the $(10\ifmmode\times\else\texttimes\fi{}10)$ unit cell of graphene matches a $(9\ifmmode\times\else\texttimes\fi{}9)$ cell of Ir(111). We determine the surface geometry by using a slab model containing four Ir layers, and the optimized structure is used as input for the subsequent surface embedded Green's function calculation. By taking advantage of semi-infinite calculations, we discuss mini energy gaps at the crossing of the $\ensuremath{\pi}$ band and its replicas, the Rashba-type spin splitting of the $\ensuremath{\pi}$ and ${\ensuremath{\pi}}^{*}$ bands, and also the energy width of both bands arising from interactions with the energy continuum of bulk Ir bands.