title: Phonon-induced gaps in graphene and graphite observed by angle-resolved photoemission.
abstract: Mapping by angle-resolved photoemission spectroscopy of the spectral functions of graphite and graphene layers at low temperatures reveals a heretofore unreported gap of ~ 67 meV at normal emission. This gap persists to room temperature and beyond, and diminishes for increasing emission angles. We show that this gap arises from electronic coupling to out-of-plane vibrational modes at the K(¯) point in the surface Brillouin zone in accordance with conservation laws and selection rules governed by quantum mechanics. Our study suggests a new approach for characterizing phonons and electron-phonon coupling in solids.
authors.affiliation: Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3080, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.forename: Longxiang
authors.initials: L
authors.lastname: Zhang
authors.forename: M K
authors.initials: MK
authors.lastname: Brinkley
authors.forename: G
authors.initials: G
authors.lastname: Bian
authors.forename: T
authors.initials: T
authors.lastname: Miller
authors.forename: T-C
authors.initials: TC
authors.lastname: Chiang