▎ 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.