A scheme is proposed to cool a rotating mirror close to its ground state in a double-Laguerre-Gaussian-cavity optomechanical system, where an auxiliary cavity and a two-level atomic ensemble simultaneously couple to the original optomechanical cavity. By choosing parameters reasonably, we find that the cooling process of the rotating mirror can be strengthened greatly while the heating process can be suppressed effectively. We show that the proposed ground-state cooling scheme can work well no matter whether in the weak or strong coupling regime for the atomic ensemble and original cavity. Compared with previous related schemes, our scheme works in the unresolved sideband regime with fewer strict limitations for the auxiliary systems.

We investigate the magnon blockade effect in a paritytime (P T) symmetric-like three-mode cavity magnomechanical system involving the magnon-photon and magnon-phonon interactions. In the broken and unbroken P T-symmetric regions, we respectively calculate the second-order correlation function analytically and numerically and further determine the optimal value of detuning. By adjusting different system parameters, we study the different blockade mechanisms and find that the perfect magnon blockade effect can be observed under the weak parameter mechanism. Our work paves a way to achieve the magnon blockade in experiment.

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A scheme to generate mechanical squeezing of phonon mode in a hybrid cavity magnomechanical system composed of a yttrium iron garnet sphere and two auxiliary cavities and driven by a two-tone laser is proposed. It is found that the strong mechanical squeezing can be generated by optimizing the ratio of blue-detuned to red-detuned laser amplitude. However, the mechanical squeezing can not be generated when the blue-detuned laser is not applied. Furthermore, it is found that the two auxiliary cavities suppress the effect of the counter-rotating terms, leading to that the mechanical squeezing can break the 3 dB limit even when the dissipation rate of the magnon mode is much larger than the mechanical frequency. By contrast, if only one auxiliary cavity or no auxiliary cavity is coupled to magnon mode, the mechanical squeezing beyond 3 dB can not be achieved in a high dissipation of the magnon mode. This scheme provides an alternative way toward the practical implementation of mechanical squeezing in a hybrid cavity magnomechanical system.