Doping graphene to extreme limits
Recently we were able to show that the intercalation of Gd or Yb leads to a strong electron doping of the graphene, where the Fermi level is pushed to the vicinity of the van Hove singularity at the M-point in graphene’s Brilloiun zone (Rosenzweig 2019, Link 2019). However, this extreme doping does not lead to a rigid shift of the electronic band structure but new effects and electronic structure renormalizations take place. For example at the van Hove singularity a flat band extending over almost 1 Å-1 evolves due to strong electron correlation effects. Furthermore, electron phonon coupling leads to the development of polaron replica bands as observed for the intercalation with Gd (Link 2019). For the intercalation of graphene with Yb a topological transition at the Fermi level and a continuous upshift of the Dirac point are observed by annealing, indicating a decrease in charge carrier density (Rosenzweig 2019). By additional doping with potassium adsorbed on top of the graphene, it was possible to dope the graphene beyond the van Hove singularity (Rosenzweig 2020). A record electron density of 8 x 1014 cm-2 could be achieved by potassium doping, which is more than twice as much as for pristine Yb-intercalated graphene at the van Hove singularity. For these extreme scenarios, new physics like chiral superconductivity or charge/spin-density waves are predicted. With the possibility to tune the doping either by potassium deposition or by diluting the Yb underneath the graphene, we expect that these states might be reachable.
- P. Rosenzweig, H. Karakachian, D. Marchenko, K. Küster, U. Starke, Phys. Rev. Lett. 125, 176403 (2020). Overdoping graphene beyond the van Hove Singularity.
- P. Rosenzweig, H. Karakachian, S. Link, K. Küster, U. Starke, Phys. Rev. B 100, 035445 (2019). Tuning the doping level of graphene in the vicinity of the Van Hove singularity via ytterbium intercalation.
- S. Link, S. Forti, A. Stöhr, K. Küster, M. Rösner, D. Hirschmeier, C. Chen, J. Avila, M. C. Asensio, A. A. Zakharov, T. O. Wehling, A. I. Lichtenstein, M. I. Katsnelson, U. Starke, Phys. Rev. B 100, 121407(R) (2019). Introducing strong correlation effects into graphene by gadolinium.