Regularly Multiple Double Dirac Cones In Photonic Bands And Topological Transitions Of All-Dielectric Photonic Crystals

Research on the remarkable characteristics of topological phases and topological phase transitions in various topological systems has been performed. In this paper, we propose a two-dimensional topological system composed of triangle photonic crystals (PCs) with C-3 point group symmetry, which hosts both regularly multiple fourfold-degenerate double Dirac cones and topological transitions in all-dielectric PC systems. By applying the tight-binding model to our system, we reveal the mechanism for topological transitions in the present configuration manufactured of conventional silicon material. Topological edge states at the common boundary of two different topological regions are demonstrated, which indicates that electromagnetic wave can propagate unidirectionally and robustly along the boundary with eximious transmission performance. Further, we manifest that topological edge states characterized by pseudospin-dependent unidirectional edge transport and have robustness against commonly minor defects. This flexible topological system demonstrates more abundant physics principles compared with previous research, which can be used to explore different topological phenomena and be implemented in integrated optical devices.