Topological nodal line states in three-dimensional ball-and-stick sonic crystals
Topological nodal line states in three-dimensional ball-and-stick sonic crystals
复制标题
三维球棒声波晶体中的拓扑节点线态
DOI：
10.1103/physrevb.100.224105
复制
发表时间：
2019-12-18
影响因子：
3.7
通讯作者：
Zhu, Xue-Feng
中科院分区：
文献类型：
--
作者：
Geng, Zhi-Guo;Peng, Yu-Gui;Zhu, Xue-Feng
电子系统中的节点线态是三维（3D）动量空间中扩展的能带交叉，最近在模拟的经典系统中得到了广泛的探索。对于二维 (2D) 六角晶格中的狄拉克锥，堆叠 2D 六角晶格（3D 晶格）中的线性简并点被拉长为动量空间中的简并线。在这项工作中，我们证明，通过耦合具有时间反演对称性和反演对称性的堆叠六方晶格，简并点将在强耦合状态下的动量空间中形成闭合的节环。我们观察到带隙中平坦的鼓面色散表面，这验证了有趣的节点线状态的存在。基于全波模拟，我们展示了截断表面处的场限制以及由于平带中的大态密度而导致的场增强。此外，还针对各种随机分布的缺陷（例如位点紊乱和跳跃紊乱）研究了鼓面表面状态的拓扑鲁棒性。我们的工作可以作为基于声波晶体的半金属的平台，用于声音捕获、振动隔离和吸收等多种应用。
Nodal line states in electronic systems are the extended band crossings in three-dimensional (3D) momentum space, which recently has been widely explored in classical systems in analogs. With the Dirac cones in two-dimensional (2D) hexagonal lattices, the linear degeneracy points in the stacking 2D hexagonal lattices (3D lattices) are elongated into degeneracy lines in the momentum space. In this work, we show that by coupling the stacked hexagonal lattices with the time-reversal symmetry and inversion symmetry protected, degeneracy points will form a closed nodal ring in the momentum space in the strong coupling regime. We observe flat drumhead dispersion surfaces in the band gaps, which verifies the existence of the intriguing nodal line states. Based on full-wave simulations, we show the field confinement at the truncated surface and the field enhancement due to the large density of states in flat bands. Furthermore, topological robustness of the drumhead surface states is investigated against various randomly distributed defects, such as site disorders and hopping disorders. Our work may serve as the platform of the sonic-crystal based semimetal for versatile applications like sound trapping, vibration isolation, and absorption.