Comparative study of Hermitian and non-Hermitian topological dielectric photonic crystals

Abstract

The effects of gain and loss on the band structures of a bulk topological dielectric photonic crystal (PC) with $C_{6v}$ symmetry and the PC-air-PC interface are studied based on first-principle calculation. To illustrate the importance of parity-time (PT) symmetry, three systems are considered, namely the PT-symmetric, PT-asymmetric, and lossy systems. We find that the system with gain and loss distributed in a PT symmetric manner exhibits a phase transition from a PT exact phase to a PT broken phase as the strength of the gain and loss increases, while for the PT-asymmetric and lossy systems, no such phase transition occurs. Furthermore, based on the Wilson loop calculation, the topology of the PT-symmetric system in the PT exact phase is demonstrated to keep unchanged as the Hermitian system. At last, different kinds of edge states in Hermitian systems under the influences of gain and loss are studied and we find that while the eigenfrequencies of nontrivial edge states become complex conjugate pairs, they keep real for the trivial defect states.

6 pages, 6 figures

References in corpus (3)

• Scheme to Achieve Silicon Topological Photonics
• First-principle calculation of Chern number in gyrotropic photonic crystals
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Cited by in corpus (6)

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• Topological Phases of Photonic Crystals under Crystalline Symmetries
• Large-area quantum-spin-Hall waveguide states in a three-layer topological photonic crystal heterostructure
• Non-Hermitian Second-Order Topological Phases and Bipolar Skin Effect in Photonic Kagome Crystals
• Single-mode lasing based on PT-breaking of two-dimensional photonic higher-order topological insulator
• Electric polarization and its quantization in one-dimensional non-Hermitian chains