title: Reduction of the superconducting gap of ultrathin Pb islands grown on Si(111).
abstract: The energy gap Delta of superconducting Pb islands grown on Si(111) was probed in situ between 5 and 60 monolayers by low-temperature scanning tunneling spectroscopy. Delta was found to decrease from its bulk value as a function of inverse island thickness. Corresponding T_{c} values, estimated using bulk gap-to-T_{c} ratio, are in quantitative agreement with ex situ magnetic susceptibility measurements, however, in strong contrast to previous scanning probe results. Layer-dependent ab initio density functional calculations for freestanding Pb films show that the electron-phonon coupling constant, determining T_{c}, decreases with diminishing film thickness.
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne (EPFL), Institut de Physique de la Matière Condensée, CH-1015 Lausanne, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Brun
authors.forename: I-Po
authors.initials: IP
authors.lastname: Hong
authors.forename: François
authors.initials: F
authors.lastname: Patthey
authors.forename: I Yu
authors.initials: IY
authors.lastname: Sklyadneva
authors.forename: R
authors.initials: R
authors.lastname: Heid
authors.forename: P M
authors.initials: PM
authors.lastname: Echenique
authors.forename: K P
authors.initials: KP
authors.lastname: Bohnen
authors.forename: E V
authors.initials: EV
authors.lastname: Chulkov
authors.forename: Wolf-Dieter
authors.initials: WD
authors.lastname: Schneider