Strain-induced topological insulating behavior in ternary chalcogenide Ge ₂Sb ₂Te ₅

We unraveled the strain-induced topological insulating behavior in Ge ₂Sb ₂Te ₅ (GST) by means of ab initio calculations. The semiconductor-to-topological-insulator (TI) transition of Ge ₂Sb ₂Te ₅ were induced by the strains along the 〈100〉 and 〈110〉 direction as well as the shear strains. Ge ₂Sb ₂Te ₅ exhibits three types of TI-characterized conducting surface states: the single Dirac cone feature, the odd band-type and the Bi ₂Se ₃-type. The physical origin of the semiconductor-TI transition is the strain-induced inversion of the characterizations of conduction band minimum and valence band maximum with spin-orbit coupling. The present results suggest that GST-related materials are a new family of strain-induced TI.