Regensburg 2019 – scientific programme

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DS: Fachverband Dünne Schichten

DS 21: Focus Session: Growth, Properties and Application of Epitaxial Graphene (joint session DS/HL/O)

DS 21.4: Talk

Thursday, April 4, 2019, 10:30–10:45, H32

Tuning the doping level of graphene near the Van Hove singularity via ytterbium intercalation — •Hrag Karakachian, Philipp Rosenzweig, Stefan Link, Kathrin Müller, and Ulrich Starke — Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, 70569 Stuttgart, Germany

At extremely high doping levels, when pushing the Fermi level to the vicinity of graphene’s Van Hove singularity (VHs), exotic electronic ground states are expected to occur driven by many-body interactions. These competing electronic phases such as chiral superconductivity, charge or spin density waves, find their stability based on the amount of doping induced in the graphene layer [1]. In this work, we present a method for effectively tuning graphene’s doping level near its VHs. Epitaxially grown graphene on SiC(0001) is decoupled from the SiC substrate and strongly n-doped up to its VHs via ytterbium intercalation. By annealing the graphene/Yb system at different temperatures, a topological transition at the Fermi level is observed and a continuous shift in Dirac point energy is measured, indicating a change in carrier density. The Yb atoms go through different order patterns at different heating stages, and their concentration is modified as a function of temperature. These variations significantly affect the amount of charge transferred to the graphene layer and allow the systematic control of graphene’s doping level near its VHs. Thus, the Yb intercalation technique can provide a reliable way of accessing and switching between different possible ordered electronic ground states in graphene.

[1] A.M. Black-Schaffer et al., J. Phys. CM 26, 423201 (2014).