Controlling exceptional points of layered non-Hermitian structures with magnetic field

Exceptional points are the characteristic features of non-Hermitian systems providing numerous applications in optics, acoustics, electronics, etc. We show that exceptional points can be controlled with the external magnetic field by considering the archetypal three-layered $\mathcal{P}\mathcal{T}$-symmetric photonic structure including a magneto-optic material between the loss and gain layers. Application of the magnetic field makes the system anisotropic with the polarization-sensitive reflection and transmission properties. As a result, the magnetic field can stimulate $\mathcal{P}\mathcal{T}$-symmetry breaking and mode exchange at realistic values of system parameters. Moreover, we suggest that the proposed scheme can be also used for magnetic-perturbation sensing with an easily adaptable level of desired field strength. Our results contain a valuable evidence for the usefulness of anisotropic (including magnetic) materials for tunable non-Hermitian photonics.