Electronic structure and electron-phonon coupling of doped graphene layers in KC8

Abstract

PACS number s : 71.10. w.-- et al. ; We propose graphite intercalation compounds GICs as a material system with precisely the same electronic properties as doped few layer graphene. Despite the fact that GICs have been around for the last four decades, this fact has gone unnoticed so far. Especially, we focus on the electronic energy bands of KC8 which correspond to a doped graphene monolayer. We provide extensive theoretical and experimental evidence for this claim employing a combined angle-resolved photoemission and theory approach using tight-binding, standard density-functional theory and including electron-electron correlation on a GW level. We observe a strong momentum-dependent kink in the quasiparticle dispersion at 166 meV highlighting electron-phonon coupling to an in-plane transversal optical phonon. These results are key for understanding both the unique electronic properties of doped graphene layers and superconductivity in KC8. ; A.G. acknowledges an APART Fellowship from the Austrian Academy of Sciences and a Marie Curie Individual Fellowship COMTRANS from the European Union. T.P. acknowledges DFG under Project No. PI 440/3/4/5. C.A. and A.R. acknowledge funding by the Spanish MEC Grant No. FIS2007-65702-C02-01 , "Grupos Consolidados UPV/EHU del Gobierno Vasco" Grant No. IT-319-07 , and the European Community through NoE Nanoquanta Grant No. NMP4-CT-2004-500198 , e-I3 ETSF Project INFRA-2007-1.2.2: Grant No. 211956 , and SANES Grant No. NMP4-CT-2006-017310 . The computer resources were provided by the Barcelona Supercomputing Center and the Basque Country University UPV/EHU SGIker Arina and ETSF. D.V. acknowledges DFG under Project No. VY64/1-1. J.F. acknowledges and appreciates financial support by the DFG Forschergruppe No. FOR 538). ; Peer reviewed