title: Hot carrier relaxation of Dirac fermions in bilayer epitaxial graphene.
abstract: Energy relaxation of hot Dirac fermions in bilayer epitaxial graphene is experimentally investigated by magnetotransport measurements on Shubnikov-de Haas oscillations and weak localization. The hot-electron energy loss rate is found to follow the predicted Bloch-Grüneisen power-law behaviour of T(4) at carrier temperatures from 1.4 K up to ∼100 K, due to electron-acoustic phonon interactions with a deformation potential coupling constant of 22 eV. A carrier density dependence n(e)(-1.5) in the scaling of the T(4) power law is observed in bilayer graphene, in contrast to the n(e)(-0.5) dependence in monolayer graphene, leading to a crossover in the energy loss rate as a function of carrier density between these two systems. The electron-phonon relaxation time in bilayer graphene is also shown to be strongly carrier density dependent, while it remains constant for a wide range of carrier densities in monolayer graphene. Our results and comparisons between the bilayer and monolayer exhibit a more comprehensive picture of hot carrier dynamics in graphene systems.
authors.affiliation: Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK.
authors.forename: J
authors.initials: J
authors.lastname: Huang
authors.forename: J A
authors.initials: JA
authors.lastname: Alexander-Webber
authors.forename: T J B M
authors.initials: TJ
authors.lastname: Janssen
authors.forename: A
authors.initials: A
authors.lastname: Tzalenchuk
authors.forename: T
authors.initials: T
authors.lastname: Yager
authors.forename: S
authors.initials: S
authors.lastname: Lara-Avila
authors.forename: S
authors.initials: S
authors.lastname: Kubatkin
authors.forename: R L
authors.initials: RL
authors.lastname: Myers-Ward
authors.forename: V D
authors.initials: VD
authors.lastname: Wheeler
authors.forename: D K
authors.initials: DK
authors.lastname: Gaskill
authors.forename: R J
authors.initials: RJ
authors.lastname: Nicholas