Topological Valley Transport in Honeycomb Photonic Crystals

The extensive research of two-dimensional layered materials has resealed that valley, as energy extrema in momentum space, could offer a new degree of freedom for carrying information. Based on this concept, researchers have forecasted valley-Hall topological insulators that can support valley-polarized edge states at nontrivial domain walls. This paper presents the design of a triangular star-shaped valley Hall photonic crystal insulator based on a hexagonal honeycomb structure. Finite element method is employed to simulate the band structure of the photonic crystal. Two types of valley Hall boundary states are designed based on the triangular star structure. Their ability to support unidirectional transmission without scattering is verified by the constructed waveguides from these boundary states.