title: Observation of plasmarons in quasi-freestanding doped graphene.
abstract: A hallmark of graphene is its unusual conical band structure that leads to a zero-energy band gap at a single Dirac crossing point. By measuring the spectral function of charge carriers in quasi-freestanding graphene with angle-resolved photoemission spectroscopy, we showed that at finite doping, this well-known linear Dirac spectrum does not provide a full description of the charge-carrying excitations. We observed composite "plasmaron" particles, which are bound states of charge carriers with plasmons, the density oscillations of the graphene electron gas. The Dirac crossing point is resolved into three crossings: the first between pure charge bands, the second between pure plasmaron bands, and the third a ring-shaped crossing between charge and plasmaron bands.
authors.affiliation: Advanced Light Source (ALS), E. O. Lawrence Berkeley Laboratory, MS6-2100, Berkeley, CA 94720, USA.
authors.forename: Aaron
authors.initials: A
authors.lastname: Bostwick
authors.forename: Florian
authors.initials: F
authors.lastname: Speck
authors.forename: Thomas
authors.initials: T
authors.lastname: Seyller
authors.forename: Karsten
authors.initials: K
authors.lastname: Horn
authors.forename: Marco
authors.initials: M
authors.lastname: Polini
authors.forename: Reza
authors.initials: R
authors.lastname: Asgari
authors.forename: Allan H
authors.initials: AH
authors.lastname: MacDonald
authors.forename: Eli
authors.initials: E
authors.lastname: Rotenberg