$\mathcal{PT}$ Symmetric Non-Hermitian Cavity Magnomechanics

TL;DR

This paper investigates PT-symmetric behavior in a non-Hermitian cavity magnomechanics system involving a ferromagnetic YIG sphere, revealing exceptional points, symmetry regions, and stability conditions relevant for quantum information applications.

Contribution

It introduces a novel PT-symmetric cavity magnomechanics system with tunable symmetry regions and stability analysis, expanding the understanding of non-Hermitian physics in hybrid systems.

Findings

Emergence of third-order exceptional points with increased magnon-photon coupling.

Identification of bi-broken and uni-protected PT-symmetry regions in eigenvalue spectrum.

System stability is only maintained at specific incident angles and coupling conditions.

Abstract

We design and explore PT-symmetric behavior of a hybrid non-Hermitian cavity magnomechanics consisting of a ferromagnetic YIG sphere driven by external magnetic field. Non-Hermicity is engineered by using a traveling field directly interacting with YIG. The external magnetic field excites collective mechanical modes of magnons, which later excites cavity mode leading to a coupling between cavity magnons and photons. The magnomechanical interaction of the system also excites phonon and couple them to the system. By computing eigenvalue spectrum, we demonstrate the occurrence of three-order exceptional point emerge with the increase of magnon-photon coupling at a specific incidence angle of traveling field. We illustrate the unique bi-broken and uni-protected PT-symmetry regions in eigenvalue spectrum unlike previously investigated non-Hermitian system, which can be tuned with gain and loss configuration by manipulating ratio between traveling field strength and magnon-photon coupling. Interestingly, protected PT-symmetry only exists on the axis of exceptional point. We further show that the PT-symmetry can only be govern at two angle of incident of traveling field. However, later, by performing stability analysis, we illustrate that the system is only stable at $\pi/2$ and, on all other angles, either the system is non-PT-symmetric or it is unstable. Furthermore, we govern the parametric stability conditions for the system and, by defining stablity parameter, illustrate the stable and unstable parametric regimes. Our finding not only discusses a new type of PT-symmetric system, but also could act as foundation to bring cavity magnomechanics to the subject of quantum information and process.