Topological phase transition and robust pseudospin interface states induced byangular perturbation in 2D topological photonic crystals

Abstract

In recent years the research about topological photonic structures has been a very attractivetopic in nanoscience from both a basic science and a technological point of view. In this work wepropose a two-dimensional topological photonic structure, composed of a trivial and a topologicalphotonic crystals, made of dumbbell-shaped dielectric rods. The topological behavior is inducedby introducing an angular perturbation in the dumbbell-shaped dielectric rods. We show that thiscomposed structure supports pseudospin interface states at the interface between the trivial andtopological crystals. Our numerical results show that a bandgap is opened in the band structure byintroducing the angular perturbation in the system, lifting the double degeneracy of the double Diraccone at the Γ point of the Brillouin zone, despite keeping the C6 symmetry group. A pseudospintopological behavior was observed and analyzed with emphasis on the photonic bands at the Γ point.We have also investigated the robustness of these pseudospin interface states and, according with ournumerical results, we conclude that they are robust against defects, disorder and reflection. Finally,we have shown that the two edge modes present energy flux propagating in opposite directions,which is the photonic analogue of the quantum spin Hall effect.