  Soliton microcombs based on Kerr nonlinearity in microresonators have been a
prominent miniaturized coherent light source. Here, for the first time, we
demonstrate the existence of Kerr solitons in an optomechanical microresonator,
for which a nonlinear model is built by incorporating a single mechanical mode
and multiple optical modes. Interestingly, an exotic vibrational Kerr soliton
state is found, which is modulated by a self-sustained mechanical oscillation.
Besides, the soliton provides extra mechanical gain through the optical spring
effect, and results in phonon lasing with a red-detuned pump. Various nonlinear
dynamics is also observed, including limit cycle, higher periodicity, and
transient chaos. This work provides a guidance for not only exploring many-body
nonlinear interactions, but also promoting precision measurements by featuring
superiority of both frequency combs and optomechanics.
