Xie Boyang, Liu Hui, Cheng Hua, Liu Zhengyou, Tian Jianguo, Chen Shuqi
The Key Laboratory of Weak Light Nonlinear Photonics, Ministry of Education, School of Physics, TEDA Institute of Applied Physics, and Renewable Energy Conversion and Storage Center, Nankai University, 300071, Tianjin, China.
The Key Laboratory of Artificial Micro- and Nanostructures of the Ministry of Education and School of Physics and Technology, Wuhan University, 430072, Wuhan, China.
Light Sci Appl. 2020 Dec 22;9(1):201. doi: 10.1038/s41377-020-00416-2.
A four-fold-degenerate three-dimensional (3D) Dirac point, represents a degenerate pair of Weyl points carrying opposite chiralities. Moreover, 3D Dirac crystals have shown many exotic features different from those of Weyl crystals. How these features evolve from 3D Dirac to Weyl crystals is important in research on 3D topological matter. Here, we realized a pair of 3D acoustic Dirac points from band inversion in a hexagonal sonic crystal and observed the surface states and helical interface states connecting the Dirac points. Furthermore, each Dirac point can transition into a pair of Weyl points with the introduction of chiral hopping. The exotic features of the surface states and interface states are inherited by the resulting Weyl crystal. Our work may serve as an ideal platform for exploring exotic physical phenomena in 3D topological semimetals.
一个四重简并的三维（3D）狄拉克点，代表一对具有相反手性的简并外尔点。此外，三维狄拉克晶体展现出许多与外尔晶体不同的奇异特性。这些特性如何从三维狄拉克晶体演变为外尔晶体，在三维拓扑物质的研究中至关重要。在这里，我们通过六角形声子晶体中的能带反转实现了一对三维声学狄拉克点，并观测到连接狄拉克点的表面态和螺旋界面态。此外，通过引入手性跳跃，每个狄拉克点可以转变为一对外尔点。所得外尔晶体继承了表面态和界面态的奇异特性。我们的工作可能成为探索三维拓扑半金属中奇异物理现象的理想平台。
