Brillouin scattering study of low-frequency bulk acoustic phonons in multilayer graphene

The low-frequency acoustic dynamics of multilayer graphene flakes, on SiO2/Si substrate, have been studied by polarized Brillouin light scattering. Interference enhancement affords the first observation of both the in-plane longitudinal and transverse acoustic bulk modes near the Γ-point of the Brillouin zone. The experimental data yielded information on the acoustic and elastic properties of multilayer graphene. Additionally, the measured phonon dispersion is found to be in good accordance with that evaluated for graphene, based on first-principles calculations within the generalized gradient approximation. Our findings strongly suggest that the interaction between layers in multilayer graphene is weak.