High-order topological insulators (TIs) develop the conventional bulk-boundary correspondence theory and rise the interest in searching innovative topological materials. To realize a high-order TI with a wide passband of 1D and 2D transportation modes, we design non-trivial and trivial 3D sonic crystals whose combination mimics the Su-Schrieffer-Heeger model. The high-order topological boundary states can be found at the interfaces, including 0D corner state, 1D hinge state, and 2D surface state. The fabricated sample with the bent two-dimensional and one-dimensional acoustic channels exhibits the multidimensional sound propagation in space, and also verifies the transition between the complete band gap, hinge states, and surface states within the bulk band gap. Among them, the bandwidth of the single-mode hinge state achieves a large relative bandwidth 9.1%, in which sound transports one-dimensionally without significant leak into the surfaces or the bulk. The high-order topological states in the study pave the way for multidimensional sound manipulation in space.

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3D声学高阶拓扑绝缘体中多维声音传播的实现

高阶拓扑绝缘体 (TI) 发展了传统的体边界对应理论，并引起了人们对寻找创新拓扑材料的兴趣。为了实现具有宽通带的 1D 和 2D 传输模式的高阶 TI，我们设计了非平凡和平凡的 3D 声波晶体，其组合模仿了 Su-Schrieffer-Heeger 模型。可以在界面处找到高阶拓扑边界状态，包括 0D 角状态、1D 铰链状态和 2D 表面状态。具有弯曲二维和一维声通道的制造样品展示了空间中的多维声音传播，并验证了完整带隙、铰链态和体带隙内表面态之间的转变。他们之中，单模铰链态的带宽实现了 9.1% 的较大相对带宽，其中声音在一维传输，而不会显着泄漏到表面或主体中。研究中的高阶拓扑状态为空间中的多维声音处理铺平了道路。