Electronic Structure of the Weak Topological Insulator Candidate Zintl Ba₃Cd₂Sb₄

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 Ba₃Cd₂Sb₄ and another related material Ba₃Cd₂As₄. 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 Ba₃Cd₂Sb₄ is a WTI. The spectroscopic characterization of this Zintl Ba₃Cd₂N₄ (N = As and Sb) family materials will facilitate applications of their novel topological properties.