Dimensional hierarchy of higher-order topology in three-dimensional sonic crystals

• Published in: Nature communications Vol. 10; no. 1; pp. 5331 - 10
• Main Authors: Zhang, Xiujuan, Xie, Bi-Ye, Wang, Hong-Fei, Xu, Xiangyuan, Tian, Yuan, Jiang, Jian-Hua, Lu, Ming-Hui, Chen, Yan-Feng
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 25.11.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/119/2792/4128; 639/624/399/1015; Acoustic noise; Acoustics; Cavities; Crystals; Fabrication; Humanities and Social Sciences; Interfaces; multidisciplinary; Photonics; Science; Science (multidisciplinary); Topology; Trapping; Waveguides
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-13333-9

Wave trapping and manipulation are at the heart of modern integrated photonics and acoustics. Grand challenges emerge on increasing the integration density and reducing the wave leakage/noises due to fabrication imperfections, especially for waveguides and cavities at subwavelength scales. The rising of robust wave dynamics based on topological mechanisms offers possible solutions. Ideally, in a three-dimensional (3D) topological integrated chip, there are coexisting robust two-dimensional (2D) interfaces, one-dimensional (1D) waveguides and zero-dimensional (0D) cavities. Here, we report the experimental discovery of such a dimensional hierarchy of the topologically-protected 2D surface states, 1D hinge states and 0D corner states in a single 3D system. Such an unprecedented phenomenon is triggered by the higher-order topology in simple-cubic sonic crystals and protected by the space group P m 3 ¯ m . Our study opens up a new regime for multidimensional wave trapping and manipulation at subwavelength scales, which may inspire future technology for integrated acoustics and photonics. Here, the authors report the experimental discovery of such a dimensional hierarchy of the topologically-protected 2D surface states, 1D hinge states and 0D corner states in a single 3D acoustic system by using higher-order topological sonic crystals.