At very high doping levels the van Hove singularity in the π∗ band of graphene becomes occupied and exotic ground states possibly emerge, driven by many-body interactions. Employing a combination of ytterbium intercalation and potassium adsorption, we n dope epitaxial graphene on silicon carbide past the π∗ van Hove singularity, up to a charge carrier density of 5.5×1014 cm−2. This regime marks the unambiguous completion of a Lifshitz transition in which the Fermi surface topology has evolved from two electron pockets into a giant hole pocket. Angle-resolved photoelectron spectroscopy confirms these changes to be driven by electronic structure renormalizations rather than a rigid band shift. Our results open up the previously unreachable beyond-van-Hove regime in the phase diagram of epitaxial graphene, thereby accessing an unexplored landscape of potential exotic phases in this prototype two-dimensional material.
@article{arxiv.2009.04876,
title = {Overdoping graphene beyond the van Hove singularity},
author = {Philipp Rosenzweig and Hrag Karakachian and Dmitry Marchenko and Kathrin Küster and Ulrich Starke},
journal= {arXiv preprint arXiv:2009.04876},
year = {2020}
}