  We report on the fabrication and operation of a multi-element vibrational
structure consisting of two graphene mechanical resonators coupled by a
nanotube beam. The whole structure is suspended. Each graphene resonator is
clamped by two metal electrodes. The structure is fabricated using a
combination of electron-beam lithography and atomic-force microscopy
nano-manipulation. This layout allows us to detect the mechanical vibrations
electrically. The measured eigenmodes are localized in either one of the
graphene resonators. The coupling due to the nanotube is studied by measuring
the shift of the resonance frequency of one graphene resonator as a function of
the vibration amplitude of the other resonator. Coupled graphene resonators
hold promise for the study of nonlinear dynamics, the manipulation of
mechanical states, and quantum non-demolition measurements.
