Cho Soohyun, Park Jin-Hong, Huh Soonsang, Hong Jisook, Kyung Wonshik, Park Byeong-Gyu, Denlinger J D, Shim Ji Hoon, Kim Changyoung, Park Seung Ryong
State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences, Shanghai, 200050, People's Republic of China.
Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea.
Sci Rep. 2021 Jan 18;11(1):1684. doi: 10.1038/s41598-020-79672-6.
It was recently reported that circular dichroism in angle-resolved photoemission spectroscopy (CD-ARPES) can be used to observe the Berry curvature in 2H-WSe (Cho et al. in Phys Rev Lett 121:186401, 2018). In that study, the mirror plane of the experiment was intentionally set to be perpendicular to the crystal mirror plane, such that the Berry curvature becomes a symmetric function about the experimental mirror plane. In the present study, we performed CD-ARPES on 2H-WSe with the crystal mirror plane taken as the experimental mirror plane. Within such an experimental constraint, two experimental geometries are possible for CD-ARPES. The Berry curvature distributions for the two geometries are expected to be antisymmetric about the experimental mirror plane and exactly opposite to each other. Our experimental CD intensities taken with the two geometries were found to be almost opposite near the corners of the 2D projected hexagonal Brillouin zone (BZ) and were almost identical near the center of the BZ. This observation is well explained by taking the Berry curvature or the atomic orbital angular momentum (OAM) into account. The Berry curvature (or OAM) contribution to the CD intensities can be successfully extracted through a comparison of the CD-ARPES data for the two experimental geometries. Thus, the CD-ARPES experimental procedure described provides a method for mapping Berry curvature in the momentum space of topological materials, such as Weyl semimetals.
最近有报道称，角分辨光电子能谱中的圆二色性（CD-ARPES）可用于观测2H-WSe中的贝里曲率（Cho等人，《物理评论快报》，2018年，第121卷，第186401页）。在该研究中，实验的镜面故意设置为与晶体镜面垂直，使得贝里曲率成为关于实验镜面的对称函数。在本研究中，我们以晶体镜面作为实验镜面，对2H-WSe进行了CD-ARPES实验。在这样的实验约束下，CD-ARPES有两种可能的实验几何构型。预计这两种几何构型的贝里曲率分布关于实验镜面是反对称的，且彼此完全相反。我们发现，在二维投影六边形布里渊区（BZ）的角点附近，用这两种几何构型测得的实验CD强度几乎相反，而在BZ中心附近则几乎相同。通过考虑贝里曲率或原子轨道角动量（OAM），可以很好地解释这一观测结果。通过比较两种实验几何构型的CD-ARPES数据，可以成功提取贝里曲率（或OAM）对CD强度的贡献。因此，所描述的CD-ARPES实验过程提供了一种在拓扑材料（如外尔半金属）的动量空间中绘制贝里曲率的方法。
