  Coupling mechanical degrees of freedom with plasmonic resonances has
potential applications in optomechanics, sensing, and active plasmonics. Here
we demonstrate a suspended two-wire plasmonic nano-antenna acting like a
nano-electrometer. The antenna wires are supported and electrically connected
via thin leads without disturbing the antenna resonance. As a voltage is
applied, equal charges are induced on both antenna wires. The resulting
equilibrium between the repulsive Coulomb force and the restoring elastic
bending force enables us to precisely control the gap size. As a result the
resonance wavelength and the field enhancement of the suspended optical
nano-antenna (SONA) can be reversibly tuned. Our experiments highlight the
potential to realize large bandwidth optical nanoelectromechanical systems
(NEMS).
