Regensburg 2019 – wissenschaftliches Programm
O 17.8: Poster
Montag, 1. April 2019, 17:45–20:00, Poster F
Graphene at its Van Hove singularity and beyond — •Philipp Rosenzweig1, Hrag Karakachian1, Dmitry Marchenko2, Kathrin Müller1, and Ulrich Starke1 — 1Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart, Germany — 2Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, 12489 Berlin, Germany
By intercalating ytterbium atoms underneath the carbon buffer layer on SiC(0001) we induce strong n-type doping in the resulting graphene monolayer. The π-band system shifts down such that the Van Hove singularity connecting K and K′ via M reaches the Fermi level EF. The Fermi surface thus undergoes a Lifshitz transition, consisting of a single giant pocket around Γ as opposed to two pockets centered at K and K′ for moderately-doped graphene systems. In addition, severe hybridization is observed between the graphene π-bands and the Yb 4f core levels near EF, which might induce considerable spin-orbit splitting of graphene’s Dirac cone [Marchenko et al., Nat. Commun. 3, 1232 (2012)]. We further show that the doping level can be enhanced by potassium adsorption at cryogenic temperatures whereas sequential annealing at elevated temperatures leads to a gradual decrease in carrier density. Thus, via precise tuning of the experimental parameters, coherent control of graphene’s doping level in the vicinity of its Van Hove singularity is achieved and the Lifshitz transition is observed in situ. Our studies might contribute to the experimental realization of exotic ground states in highly-doped graphene such as chiral superconductivity [Nandkishore et al., Nat. Phys. 8, 152 (2012)].