Topological phase transition in centered rectangular photonic lattice: toward photonic topological insulator

A Cm planar two-dimensional photonic crystal, related to the centered rectangular lattice, with line (mirror reflection) symmetry is investigated wherein the Dirac cones appear at the high symmetry points of the Brillouin zone boundary. A bridge can be made between an ordinary insulator, zero-spin Chern number (Cs) and the topological insulator non-zero Cs, through the topological phase transition when we introduce a unique perturbation on the photonic structure. The perturbation can be realized by the mismatch of the lattice symmetry planes due to breaking the mirror symmetry of the unit cell. Through this modification, one of the topological phase transition characterizations, directional band gap and band inversion, will be happen. The proposed photonic crystal may be a good candidate for studying the one -way propagation of waves at the topological interfaces to realize photonic topological insulators (PTIs).