  We propose to enhance the generation of a phonon laser by exploiting optical
superradiance. In our scheme, the optomechanical cavity contains a movable
membrane, which supports a mechanical mode, and the superradiance cavity can
generate the coherent collective light emissions by applying a transverse pump
to an ultracold intracavity atomic gas. The superradiant emission turns out to
be capable of enhancing the phonon laser performance. This indicates a new way
to operate a phonon laser with the assistance of coherent atomic gases trapped
in a cavity or lattice potentials.
