Landau level spectroscopy of graphene: exploring the influence of doping, edges and charged impurities

Full text: Scanning tunnelling microscopy and spectroscopy (STM/STS) provides direct access to the quasiparticles in graphene and to their interactions with the environment and with each other through the local density of states. I will describe STM/STS experiments which explore the evolution of the density of states with magnetic field into Landau levels, their dependence on doping and on proximity to a zigzag edge. We have found that the effect of a charged impurity on the spectrum strongly depends on Landau level filling. For a partially filled level the impurity is efficiently screened, becoming essentially invisible at small filling factors. By contrast, for filled Landau levels where screening is absent, the impurity induces large shifts in the local Landau level energy and lifts the orbital degeneracy. (authors) References: [1] G. Li, A. Luican, D. Abanin, L. Levitov and E. Y. Andrei, arxiv1203.5540 [2] A. Luican, G. Li and E.Y. Andrei, Phys. Rev. Lett. 106, 126802 (2011) [3] G. Li, A. Luican and E. Y. Andrei Phys. Rev. Lett 102, 176804 (2009)