A Dirac semimetal phase diagram of the binary compound CuI(R-3m)

Abstract

Based on first-principles calculations, we study the properties and interactions of the existing binary compound CuI with the space group of R-3m. A pair of Dirac points with asymmetry high Fermi velocity is found to be distributed on the unique C3 symmetry axis in k space, which are formed by band inversion between I- |32,±32〉 and |32,±12〉 type states. CuI(R-3m) is located at the boundary of different topological phases. Anisotropic strain breaking C3 symmetry could switch CuI(R-3m) between topological Dirac semimetal state and strong topological insulator states. A Dirac semimetal phase diagram is obtained, and show that binary compound with the space group of R-3m is a good platform for getting different semi-metals states. We reveal that various topological phases can be achieved in the binary compounds with the space group of R-3m (NO.166) by regulating the on-site energy difference and the SOC strength. The compounds family of XY (X = Cu, Ag, Au; YI, Br, Cl, F) with the atomic structure of CuI(R-3m) are topological semimetals with one or two pairs of Dirac points around Fermi energy, except for AgCl and AgF.