title: Reversible phase transformation and doubly charged anions at the surface of simple cubic RbC60.
abstract: The simple cubic phase of a RbC60 thin film has been studied using photoelectron spectroscopy. The simple cubic-to-dimer transition is found to be reversible at the film surface. A sharp Fermi edge is observed and a lower limit of 0.5 eV is found for the surface Hubbard U, pointing to a strongly correlated metallic character of thin-film simple cubic RbC60. A molecular charge state is identified in the valence band and core-level photoemission spectra which arises from C60(2-) anions and contributes to the spectral intensity at the Fermi level.
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands. roberto.macovez@icfo.es
authors.forename: Roberto
authors.initials: R
authors.lastname: Macovez
authors.forename: Andrea
authors.initials: A
authors.lastname: Goldoni
authors.forename: Luca
authors.initials: L
authors.lastname: Petaccia
authors.forename: Ingrid
authors.initials: I
authors.lastname: Marenne
authors.forename: Paul A
authors.initials: PA
authors.lastname: Brühwiler
authors.forename: Petra
authors.initials: P
authors.lastname: Rudolf