Inhomogenous local electronic structure in overdoped graphene

Over the last two decades, graphene has emerged as a platform to study a myriad of many-body interactions. For example, upon sufficiently high levels of doping the van Hove singularity (vHS) has been shown to evolve such that it has extended character instead of pointlike character in pristine graphene. Here, we investigate the effects of ytterbium intercalation on the electronic structure in a single layer of graphene using spectroscopic imaging scanning tunneling spectroscopy (SI-STM) and angle-resolved photoemission spectroscopy (ARPES). Our results demonstrate that ytterbium atoms behave as both chemical and substitutional dopants. Moreover, while the global electronic structure characterized via ARPES appears to be homogenous, SI-STM reveals substantial inhomogeneity in the local electronic structure. In particular, the energies of the vHS and Dirac cone vary considerably as a function of position. Our results suggest that the band structure of graphene undergoes significant renormalization caused by the ytterbium dopants.