Higher-order topological phases in tunable C<sub>3</sub> symmetric photonic crystals
Hai-Xiao Wang, Li Liang, Bin Jiang, Junhui Hu, Xiancong Lu, Jian-Hua Jiang
Abstract
We demonstrate that multiple higher-order topological transitions can be triggered via the continuous change of the geometry in kagome photonic crystals composed of three dielectric rods. By tuning a single geometry parameter, the photonic corner and edge states emerge or disappear with higher-order topological transitions. Two distinct higher-order topological insulator phases and a normal insulator phase are revealed. Their topological indices are obtained from symmetry representations. A photonic analog of the fractional corner charge is introduced to distinguish the two higher-order topological insulator phases. Our predictions can be readily realized and verified in configurable dielectric photonic crystals.