title: Phonon self-energy corrections to nonzero wave-vector phonon modes in single-layer graphene.
abstract: Phonon self-energy corrections have mostly been studied theoretically and experimentally for phonon modes with zone-center (q=0) wave vectors. Here, gate-modulated Raman scattering is used to study phonons of a single layer of graphene originating from a double-resonant Raman process with q≠0. The observed phonon renormalization effects are different from what is observed for the zone-center q=0 case. To explain our experimental findings, we explored the phonon self-energy for the phonons with nonzero wave vectors (q≠0) in single-layer graphene in which the frequencies and decay widths are expected to behave oppositely to the behavior observed in the corresponding zone-center q=0 processes. Within this framework, we resolve the identification of the phonon modes contributing to the G(⋆) Raman feature at 2450 cm(-1) to include the iTO+LA combination modes with q≠0 and also the 2iTO overtone modes with q=0, showing both to be associated with wave vectors near the high symmetry point K in the Brillouin zone.
authors.affiliation: Department of Electrical Engineering and Computer Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA. ptaraujo@mit.edu
authors.forename: P T
authors.initials: PT
authors.lastname: Araujo
authors.forename: D L
authors.initials: DL
authors.lastname: Mafra
authors.forename: K
authors.initials: K
authors.lastname: Sato
authors.forename: R
authors.initials: R
authors.lastname: Saito
authors.forename: J
authors.initials: J
authors.lastname: Kong
authors.forename: M S
authors.initials: MS
authors.lastname: Dresselhaus