Coupled topological states in a non-Hermitian heterostructure based on the two-dimensional SSH model

Topological mode coupling induces hybridized states with exotic phenomena. Introducing gain/loss into topological photonic systems (non-Hermitian framework) opens new physical dimensions. This work studies coupled topological edge/corner states based on two-dimensional Su-Schrieffer-Heeger (SSH) model. It demonstrates topological phase transitions at gain-loss domain interfaces of topological photonic crystals (PCs) and investigates edge/corner states in loss-gain-loss structures. Numerical results show non-Hermitian topological states have better edge/corner localization than Hermitian ones. This advances non-Hermitian Dirac physics understanding and provides a platform for photonic device applications.