Engineering the unidirectional topological excitation transmission and topological diode in the Rice-Mele model

We show how to implement the unidirectional topological excitation transmission in the Rice-Mele model. We find that the unidirectional excitation transmissions can be implemented via the asymmetric gap states. We reveal that the asymmetric gap states are essentially induced by the breaking of generalized chiral symmetry and the gap state without band crossing determines the transmission direction. In particular, we find that the direction of the unidirectional edge transmission can be reversed via setting the band inversion or mirror symmetry. The unidirectional excitation transmissions based on gap states can be equivalent to a topological diode with properties of unidirectional conduction, which may have potential applications in the implementation of new-type topological devices, e.g., a topological sensor or topological switch.