title: Absence of photoemission from the Fermi level in potassium intercalated picene and coronene films: structure, polaron, or correlation physics?
abstract: The electronic structure of potassium intercalated picene and coronene films has been studied using photoemission spectroscopy. Picene has additionally been intercalated using sodium. Upon alkali metal addition core level as well as valence band photoemission data signal a filling of previously unoccupied states of the two molecular materials due to charge transfer from potassium. In contrast to the observation of superconductivity in K(x)picene and K(x)coronene (x ~ 3), none of the films studied shows emission from the Fermi level, i.e., we find no indication for a metallic ground state. Several reasons for this observation are discussed.
authors.affiliation: IFW Dresden, P. O. Box 270116, D-01171 Dresden, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Mahns
authors.forename: Friedrich
authors.initials: F
authors.lastname: Roth
authors.forename: Martin
authors.initials: M
authors.lastname: Knupfer