1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 2University of Chinese Academy of Sciences, Beijing 100049, China 3Department of Physics, Renmin University of China, Beijing 100872, China 4Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China 5Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201204, China 6School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710119, China 7Songshan Lake Materials Laboratory, Dongguan 523808, China 8CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
Abstract：One of the greatest triumph of condensed matter physics in the past ten years is the classification of materials by the principle of topology. The existence of topological protected dissipationless surface state makes topological insulators great potential for applications and hotly studied. However, compared with the prosperity of strong topological insulators, theoretical predicted candidate materials and experimental confirmation of weak topological insulators (WTIs) are both extremely rare. By combining systematic first-principles calculation and angle-resolved photoemission spectroscopy measurements, we have studied the electronic structure of the dark surface of the WTI candidate Zintl Ba$_{3}$Cd$_{2}$Sb$_{4}$ and another related material Ba$_{3}$Cd$_{2}$As$_{4}$. The existence of two Dirac surface states on specific side surfaces predicted by theoretical calculations and the observed two band inversions in the Brillouin zone give strong evidence to prove that the Ba$_{3}$Cd$_{2}$Sb$_{4}$ is a WTI. The spectroscopic characterization of this Zintl Ba$_{3}$Cd$_{2}N_{4}$ ($N$ = As and Sb) family materials will facilitate applications of their novel topological properties.
2023, Vol. 40 
