Topological states in Chevrel phase materials from first principles calculations

Chevrel phase materials form a family of ternary molybdenum chalcogenides with a general chemical formula A(x)Mo(6)X(8) (A = metal elements, X = chalcogen). The variety of A atoms makes a large number of family members and leads to many tunable physical properties, such as the superconductivity, thermoelectricity, and the ionic conductivity. In this work, we have further found various nontrivial band topological states in these materials by using first-principle calculations. The compounds having time-reversal symmetry, such as BaMo6S8, SrMo6S8, and Mo6S8, are topological insulators in both of the R (3) over bar and P (1) over bar phases, whereas EuMo6S8 within ferromagnetic state is an axion insulator in the R (3) over bar phase and a trivial one in the P (1) over bar phase. This indicates that the change of A ions can modify the chemical potential, lattice distortion, and magnetic orders, which offers a unique way to influence the topological states and other properties. We hope this work can stimulate further studies of Chevrel phase materials to find more intriguing phenomena, such as topological superconducting states and Majorana modes.