Topological Ratio Transmission and Higher‐Order Topological States in Chiral Phononic Crystal by Breaking Spatial Inversion Symmetry.

Topological insulators, introduced in classical wave systems, have opened a new avenue for exploring novel topologically protected transport phenomena. Although originally constrained by the lower dimensionality of modes compared to that of topological insulators, topological edge states and higher‐order topological (HOT) states provide topological protection to extend a range of dimensionalities. Herein, the topological protection propagation and the ratio transmission in the chiral phononic crystal (CPC) by breaking the spatial inversion symmetry are realized. Theoretically, the presence of the HOT states is demonstrated. The disparities in HOT states for the monophase and nested sample consisting of two types of CPCs are elucidated. The findings demonstrate that acoustic topological states possess rich physics and provide a flexible approach to designing desired topological structures. [ABSTRACT FROM AUTHOR]