Unconventional plasmon-phonon coupling in graphene

We predict the existence of coupled plasmon-phonon excitations in graphene by using the self-consistent linear response formalism. The unique electron-phonon interaction in graphene leads to unconventional mixing of plasmon and optical phonon polarizations. We find that longitudinal plasmons couple exclusively to transverse optical phonons, whereas graphene's transverse plasmons couple only to longitudinal optical phonons. This coupling can serve as a magnifier for exploring the electron-phonon interaction in graphene, and it offers electronical control over phonon frequencies.