$\mathcal{PT}-$symmetry and chaos control via dissipative optomechanical coupling

Abstract: We study a dissipative, mechanically coupled optomechanical system that accommodates gain and loss. The gain (loss) is engineered by driven a purely dispersive optomechanical cavity with a blue-detuned (red-detuned) electromagnetic field. By taking into account the dissipative coupling, the Exceptional Point (EP), which is the $\mathcal{PT}-$symmetry phase transition, occurs at low threshold driving strength compared to the purely dispersive system. In the linear regime, the $\mathcal{PT}-$symmetry is unbroken and the dissipative coupling induces strong coupling between the mechanical resonators, leading to an increase in energy exchange. For sufficiently strong driving, the system enters into a nonlinear regime where the $\mathcal{PT}-$symmetry is broken. In this regime, the mechanical resonators exhibit chaotic beats like-behaviour in the purely dispersive system. By switching on the dissipative coupling, the complex dynamics is switched off, restoring regular dynamics to the system. This work suggests ways to probe quantum phenomena in dissipative $\mathcal{PT}-$symmetric systems at low-threshold driving strength. It also provides a new way to control complex dynamics in optomechanics and related fields.