High van Hove singularity extension and Fermi velocity increase in epitaxial graphene functionalized by intercalated gold clusters

Gold intercalation between a buffer layer and a graphene monolayer of epitaxial graphene on SiC(0001) leads to the formation of small aggregates of clusters. Angle-resolved photoemission spectroscopy measurements reveal that these clusters preserve the linear dispersion of the graphene quasiparticles and surprisingly increase their Fermi velocity. They also strongly modify the band structure of graphene around the van Hove singularities by a strong extension without charge transfer. These results give new insight on the role of the intercalant in the renormalization of the bare electronic band structure of graphene usually observed in graphite and graphene intercalation compounds.