National Laboratory of Solid State Microstructures & Department of Materials Science and Engineering, Nanjing University, Nanjing, 210093, China.
Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
Nat Commun. 2023 Feb 20;14(1):952. doi: 10.1038/s41467-023-36511-2.
Fermionic time-reversal symmetry ([Formula: see text])-protected quantum spin Hall (QSH) materials feature gapless helical edge states when adjacent to arbitrary trivial cladding materials. However, due to symmetry reduction at the boundary, bosonic counterparts usually exhibit gaps and thus require additional cladding crystals to maintain robustness, limiting their applications. In this study, we demonstrate an ideal acoustic QSH with gapless behaviour by constructing a global T on both the bulk and the boundary based on bilayer structures. Consequently, a pair of helical edge states robustly winds several times in the first Brillouin zone when coupled to resonators, promising broadband topological slow waves. We further reveal that this ideal QSH phase behaves as a topological phase transition plane that bridges trivial and higher-order phases. Our versatile multi-topology platform sheds light on compact topological slow-wave and lasing devices.
费米子时间反转对称性 ([Formula: see text]) 保护的量子自旋霍尔 (QSH) 材料在与任意平凡包层材料相邻时具有无带隙的螺旋边缘态。然而，由于边界处的对称性降低，玻色子对应物通常表现出带隙，因此需要额外的包层晶体来保持稳定性，从而限制了它们的应用。在这项研究中，我们通过在双层结构上构建全局 T 来展示具有无带隙行为的理想声学 QSH。因此，当与谐振器耦合时，一对螺旋边缘态在第一布里渊区中稳定地缠绕几圈，有望实现宽带拓扑慢波。我们进一步揭示了这个理想的 QSH 相作为一个拓扑相变平面，连接了平凡相和更高阶相。我们的多功能多拓扑平台为紧凑的拓扑慢波和激光器件提供了思路。
