Multi‐Type Topological States in Higher‐Order Photonic Insulators Based on Kagome Metal Lattices.

Tunability of topological photonic structures opens a new avenue for photonics research. The rich physical characteristics of the topological photonics have great significance in practical implementations. In this paper, multi‐type topological states are demonstrated in higher‐order photonic topological insulators based on Kagome metal lattices. By stretching or rotating Kagome metal lattices, two types of topological insulators are obtained, and multi‐type topological states are observed. By stretching Kagome metal lattices, a 1D topological edge state and two types of higher‐order topological corner states (corresponding to a traditional higher‐order topological corner state based on nearest‐neighbor coupling and a new higher‐order corner state caused by long‐range interactions) are obtained in a classical quantization of dipole moments higher‐order topological insulators. By rotating Kagome metal lattices, dual‐band higher‐order valley‐Hall topological insulators are achieved with nodal ring degeneracy. Odd‐type and even‐type topological states are obtained. Achieving reconfigurable, multi‐type, and multi‐band topological insulators by using a single structural unit provides interesting insights into topological photonics and provides an unconventional approach to explore photonic systems and condensed matter physics. [ABSTRACT FROM AUTHOR]