Abstract
Topological Dirac semimetals (TDSs) offer an excellent opportunity to realize outstanding physical properties distinct from those of topological insulators. Since TDSs verified so far have their own problems such as high reactivity in the atmosphere and difficulty in controlling topological phases via chemical substitution, it is highly desirable to find a new material platform of TDSs. By angle-resolved photoemission spectroscopy combined with first-principles band-structure calculations, we show that ternary compound BaMg2Bi2 is a TDS with a simple Dirac-band crossing around the Brillouin-zone center protected by the C3 symmetry of crystal. We also found that isostructural SrMg2Bi2 is an ordinary insulator characterized by the absence of band inversion due to the reduction of spin–orbit coupling. Thus, XMg2Bi2 (X = Sr, Ba, etc.) serves as a useful platform to study the interplay among crystal symmetry, spin–orbit coupling, and topological phase transition around the TDS phase.
Highlights
Topological Dirac semimetals (TDSs) offer an excellent opportunity to realize outstanding physical properties distinct from those of topological insulators
Angle-resolved photoemission spectroscopy (ARPES) has played a pivotal role in clarifying TDSs by directly visualizing the bulk Dirac-cone band, as demonstrated in N a3Bi, Cd3As2, and α-Sn/ InSb(111)[5,7,15,16,17,18] which host Dirac-cone bands protected by the rotational symmetry
Our first-principles band-structure calculations including spin–orbit coupling (SOC) shown in Fig. 1c reveal that B aMg2Bi2 possesses a Dirac cone close to the Fermi level (EF) along the ΓA line of bulk BZ (Fig. 1b) due to the bulk-band inversion and the protection by the C 3 symmetry, consistent with the previous c alculation[30]
Summary
Topological Dirac semimetals (TDSs) offer an excellent opportunity to realize outstanding physical properties distinct from those of topological insulators.
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