Renormalization of Dirac Cones by Correlation Effects in Heavily-Doped Graphene

A longstanding question in the field of solid-state physics is the renormalization of quasiparticles induced by the effect of electronic correlations. We employ angle-resolved photoemission spectroscopy to study quasiparticle renormalizations in graphene whose electron density can be modulated by the deposition of alkali metals. The evolution of ARPES spectra taken over a wide range of the Rb density reveals a discontinuity in the electron compressibility, which is identified as due to the phase formation of Rb atoms on graphene. We found a clear satellite feature of Dirac cones formed by correlations effects, and its coupling strength is enhanced with the phase formation of Rb atoms. Our results suggest that in graphene doped by alkali metals the phase formation of dopants should be carefully considered in a quantitative analysis on band renormalizations.