  We theoretically study a doped graphene ribbon suspended over a trench and
subject to an ac-electrical field polarized perpendicularly to the graphene
plane. In such a system, the external ac-field is coupled to the relatively
slow mechanical vibrations via plasmonic oscillations in the isolated graphene
sheet. We show that the electrical field generates an effective pumping of the
mechanical modes. It is demonstrated that in the case of underdamped plasma
oscillation, a peculiar kind of geometrical resonance of the mechanical and
plasma oscillations appear. Namely the efficiency of pumping significantly
increases when the wave number of the mechanical mode is in close agreement
with the wave number of the plasma waves. The intensity of the pumping
increases with the wave number of the mode. This phenomenon allows selective
actuation of different mechanical modes although the driving field is
homogeneous.
