  Quantum coherence is one of the most intriguing applications of quantum
mechanics, and has led to interesting phenomena and uncommon results. Here we
show that in a stark contrast to the usual red-detuned condition to observe
bistability in single-mode optomechanics, the optical intensities exhibit
bistability for all values of cavity-laser detuning due to intermode coupling
induced by the two-photon coherence. Interestingly, an unconventional
bistability with "ribbon"-shaped hysteresis can be observed for blue-detuned
laser frequencies. We also demonstrate that the two-photon coherence leads to a
strong entanglement between the movable mirrors in the adiabatic regime.
Surprisingly, the mirror-mirror entanglement is shown to persist for
environment temperature of the phonon bath up to 12 K using experimental
parameters.
