Reconfigurable topological phases in photoexcited graphene nanoribbon arrays

We introduced here a reconfigurable topological phase using optically pumped graphene nanoribbon arrays with homogeneous spacing at terahertz frequencies. By adjusting the profile of imaginary potential, various topologically non-trivial dimer chains composed of graphene nanoribbons can be selectively produced. These dimer chains support different kinds of midgap states. Moreover, we numerically demonstrated that these midgap states are robust against some perturbations, such as non-Hermitian and lattice disorders, and can be further adjusted by varying the pumping strength on the specific graphene nanoribbon. Consequently, the reconfigurable topological phase can be obtained by only tuning the profile of imaginary potential without altering the geometry of the system. These tunable topological phases may provide a convenient method to tune the spatial profile of graphene-based topological lasers and have potential applications in topologically protected waveguiding in terahertz frequency range.