Optomechanical dynamics in the $\mathcal{PT}$- and broken-$\mathcal{PT}$-symmetric regimes

Abstract

We theoretically study the dynamics of typical optomechanical systems, consisting of a passive optical mode and an active mechanical mode, in the PT -and broken-PT -symmetric regimes. By fully analytical treatments for the dynamics of the average displacement and particle numbers, we reveal the phase diagram under different conditions and the various regimes of both PT -symmetry and stability of the system. We find that by appropriately tuning either mechanical gain or optomechanical coupling, both phase transitions of the PT -symmetry and stability of the system can be flexibly controlled. As a result, the dynamical behaviors of the average displacement, photons, and phonons are radically changed in different regimes. Our study shows that PT -symmetric optomechanical devices can serve as a powerful tool for the manipulation of mechanical motion, photons, and phonons.

Higher-order exceptional point in a pseudo-Hermitian cavity optomechanical system

“…By tuning one parameter of a pseudo-Hermitian system, the quantum phase transition from the PT -symmetric phase with real eigen energies to the PT -symmetric broken phase with complex-conjugate pairs eigen energies can occur at the second-order exceptional point (EP2), where the two eigenvalues and the corresponding eigenvectors simultaneously coalesce together [28][29][30]. During the past few years, EP2s have been widely investigated in COM systems [31][32][33][34][35][36] and other systems including, e.g., waveguides [37], microcavities [44], cavity magnonics [38,39] and superconducting circuits [40,41]. Around EP2s, lots of fascinating phenomena like unidirectional invisibility [42][43][44], single-mode lasing [45,46], sensitivity enhancement [47,48], energy harvesting [49], and electromagnetically induced transparency [50][51][52][53] can be realized.…”