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arXiv · 2009.04876

Overdoping graphene beyond the van Hove singularity

Philipp Rosenzweig·Hrag Karakachian·Dmitry Marchenko·Kathrin Küster·Ulrich Starke
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Abstract

At very high doping levels the van Hove singularity in the $\pi^*$ 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 $\pi^*$ van Hove singularity, up to a charge carrier density of 5.5$\times$10$^{14}$ 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.

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Philipp Rosenzweig, Hrag Karakachian, Dmitry Marchenko, Kathrin Küster, Ulrich Starke. 2020-09-10. Overdoping graphene beyond the van Hove singularity. https://doi.org/10.1103/physrevlett.125.176403

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