Effective spin-orbital coupling determined topological properties of Half-Heusler compounds XYZ (X = Li, Na, K; Y = Ag, Au; Z = S, Se, Te)

Abstract

The topological properties of half Heusler compounds XYZ (X = Li, Na, K; YAg, Au; Z = S, Se, Te) are studied by the density functional theory and k ⋅ p method. The S-based compounds are topological insulators in both cubic and tetragonal structures, because of the negative spin-orbital coupling (SOC). While the Se and Te-based compounds are topological semimetals because of their positive SOC.