Topological phase transitions and switchable edge states for the non-Hermitian Aubry-André-Harper model in photonic crystals.

The Aubry-André-Harper (AAH) model with imaginary periodic or quasiperiodic modulations could regulate the local properties of the system. In this work, we apply the non-Hermitian AAH potential field to the photonic system induced by gain and loss. It is found that the potential field with different parameters will cause the system to exhibit different local properties and induce different localized edge states under the open boundary conditions. Moreover, we investigated the influence of non-Hermitian AAH potential parameters on the edge states of the Haldane model under periodic boundary conditions. It is shown that two-dimensional magnetic photonic crystals can undergo topological transitions and switchable edge states by tuning the potential field parameters. This offers a versatile method for controlling optical flow in photonic platforms.