Cluster-induced non-topological robust boundary states in photonic lattice

In conventional topological photonic lattices, the robustness of boundary states is guaranteed by quantized topological invariants. However, this protection mechanism is inherently tied to the system’s symmetry, making dynamic reconfiguration difficult. In this work, we introduce cluster molecules as symmetry-breaking units into the Su-Schrieffer-Heeger (SSH) lattice. By continuously tuning the cluster rotation angle, we modulate the coupling strength between the clusters and the substrate lattice, thereby enabling on-demand control of boundary states. Our findings reveal that the robustness of the boundary modes is co-determined by the cluster rotation angle and the boundary geometry, with their degree of localization showing a positive correlation with robustness—a behavior distinct from conventional global topological protection. This work establishes a geometry-driven paradigm for boundary-state manipulation, opening new pathways toward programmable and dynamically reconfigurable photonic circuits.