title: Tunable carrier multiplication and cooling in graphene.
abstract: Time- and angle-resolved photoemission measurements on two doped graphene samples displaying different doping levels reveal remarkable differences in the ultrafast dynamics of the hot carriers in the Dirac cone. In the more strongly (n-)doped graphene, we observe larger carrier multiplication factors (>3) and a significantly faster phonon-mediated cooling of the carriers back to equilibrium compared to in the less (p-)doped graphene. These results suggest that a careful tuning of the doping level allows for an effective manipulation of graphene's dynamical response to a photoexcitation.
authors.affiliation: Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL) , 1015 Lausanne, Switzerland.
authors.forename: Jens Christian
authors.initials: JC
authors.lastname: Johannsen
authors.forename: Søren
authors.initials: S
authors.lastname: Ulstrup
authors.forename: Alberto
authors.initials: A
authors.lastname: Crepaldi
authors.forename: Federico
authors.initials: F
authors.lastname: Cilento
authors.forename: Michele
authors.initials: M
authors.lastname: Zacchigna
authors.forename: Jill A
authors.initials: JA
authors.lastname: Miwa
authors.forename: Cephise
authors.initials: C
authors.lastname: Cacho
authors.forename: Richard T
authors.initials: RT
authors.lastname: Chapman
authors.forename: Emma
authors.initials: E
authors.lastname: Springate
authors.forename: Felix
authors.initials: F
authors.lastname: Fromm
authors.forename: Christian
authors.initials: C
authors.lastname: Raidel
authors.forename: Thomas
authors.initials: T
authors.lastname: Seyller
authors.forename: Phil D C
authors.initials: PD
authors.lastname: King
authors.forename: Fulvio
authors.initials: F
authors.lastname: Parmigiani
authors.forename: Marco
authors.initials: M
authors.lastname: Grioni
authors.forename: Philip
authors.initials: P
authors.lastname: Hofmann
keywords: carrier multiplication; charge carrier tunability; epitaxial graphene; hot carrier dynamics; time-resolved ARPES