Enhancement of Electron-Phonon Interaction by Band-Gap Opening in Bilayer Graphene

摘要

Electronic states and phonon energies in bilayer graphene were investigated by electrical and optical measurements under an external electric field, which was controlled by applying bias voltages to a bottom gate and a transparent ionic liquid side gate in a field-effect transistor. The transport measurements showed that the band gap was opened. The symmetric and antisymmetric optical phonons were visible in the Raman scattering spectra. Their behavior was explained by a Kohn anomaly. The mixing of symmetric and antisymmetric optical phonons was minimized by the external electric field, owing to the enhancement of electron-phonon interactions that accompanied the band-gap opening.