Graphite intercalation compound KC${}_8$ revisited: a key to graphene

Abstract

Electrons in isolated graphene layers are a two-dimensional gas of massless Dirac Fermions. In realistic devices, however, the electronic properties are modified by elastic deformations, interlayer coupling and substrate interaction. Here we unravel the electronic structure of doped graphene, revisiting the stage one graphite intercalation compound KC${}_8$ using angle--resolved photoemission spectroscopy and ab--initio calculations. The full experimental dispersion is in excellent agreement to calculations of doped graphene once electron correlations are included on the $GW$ level. This highlights that KC${}_8$ has negligible interlayer coupling. Therefore Dirac Fermion behaviour is preserved and we directly determine the full experimental Dirac cone of doped graphene. In addition we prove that superconductivity in KC${}_8$ is mediated by electron--phonon coupling to an iTO phonon, yielding a strong kink in the quasiparticle dispersion at 166 meV. These results are key for understanding, both, the unique electronic properties of graphene and superconductivity in KC${}_8$.

References in corpus (8)

• Electric Field Effect in Atomically Thin Carbon Films
• Substrate-induced band gap opening in epitaxial graphene
• Anisotropic Electron-Phonon Coupling and Dynamical Nesting on the Graphene Sheets in CaC6
• Van Hove Singularity and Apparent Anisotropy in the Electron-Phonon Interaction in Graphene
• Effect of electron-electron interaction on the Fermi surface topology of doped graphene
• Tunable hybridization of electronic states of graphene and a metal surface
• Massive enhancement of electron-phonon coupling in doped graphene by an electronic singularity
• Experimental Determination of the Spectral Function of Graphene