A photoemission study of the nature of the metallic state in single wall carbon nanotube bundles at low potassium doping

We report on the doping dependence of the valence band of mats of potassium intercalated single wall carbon nanotubes (SWCNT) using high resolution photoemission spectroscopy as probe. For the pristine SWCNT about one third are metallic Tomonaga-Luttinger-Liquids (TLL) which can be directly monitored by a power law scaling in the density of states close to the Fermi level. Upon potassium doping the charge transfer to the conduction band of the fraction of semiconducting SWCNT within the bundle leads to a crossover from the TLL scaling to a normal Fermi liquid behaviour. This can be explained by an increased intertube interaction and/or by an increased screening of the neighboring metallic tubes within the bundle.