Cerjan Alexander, Jürgensen Marius, Benalcazar Wladimir A, Mukherjee Sebabrata, Rechtsman Mikael C
Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Phys Rev Lett. 2020 Nov 20;125(21):213901. doi: 10.1103/PhysRevLett.125.213901.
Higher-order topological insulators are a recently discovered class of materials that can possess zero-dimensional localized states regardless of the dimension of the system. Here, we experimentally demonstrate that the topological corner-localized modes of higher-order topological systems can be symmetry-protected bound states in the continuum; these states do not hybridize with the surrounding bulk states of the lattice even in the absence of a bulk band gap. This observation expands the scope of bulk-boundary correspondence by showing that protected boundary-localized states can be found within topological bands, in addition to being found in between them.
高阶拓扑绝缘体是一类最近发现的材料，无论系统的维度如何，它们都可以拥有零维局域态。在这里，我们通过实验证明，高阶拓扑系统的拓扑角局域模式可以是连续统中的对称性保护束缚态；即使在没有体能带隙的情况下，这些态也不会与晶格周围的体态发生杂化。这一观察结果扩展了体-边界对应关系的范围，表明除了在拓扑能带之间可以找到受保护的边界局域态之外，在拓扑能带内部也可以找到。
