Realization of Topological Corner States in Tailored Photonic Graphene

• DOI: 10.1021/acsphotonics.3c01651
• Publication Date: 2024-01-19T17:40:25Z
• Authors: Yuqing Xie; Wenchao Yan; Shiqi Xia; Yongsheng Liang; Liqin Tang; Daohong Song; Jingjun Xu; Zhigang Chen
• Keywords: Gapless playback; Topological insulator; Lattice (music)

Higher-order topological semimetals (HOTSMs) represent a novel type of gapless phase, hosting boundary states with dimensions at least two lower than those their bulk geometry. Such nontrivial have been predicted and observed in three-dimensional (3D) systems, representing features the HOTSMs. However, two-dimensional (2D) analogs, represented especially by corner monolayer graphene-like structures, thus far remained only theoretical exploration. Here, we experimentally demonstrate specially tailored photonic graphene Dirac points, manifesting HOTSM-like property 2D setting. otherwise system exhibit distinct phase structures depending on lattice edge geometry, are completely degenerate zero-energy states. Remarkably, find that these "gapless" remain intact even finite-sized lattice, protected chiral symmetry. Unlike higher-order insulators or crystalline certain rotational symmetry, localized exclusively to one without any coupling other corners, despite long-distance propagation.