Pressure-induced topological insulating behavior in the ternary chalcogenide Ge₂Sb₂Te₅

We unraveled the pressure-induced topological insulating behavior in Ge₂Sb₂Te₅ (GST) by means of ab initio calculations. We have shown that the spin-orbit interaction separates the twofold degenerate Ge p_xp_y Sb p_xp_y Te p_xp_y state to an upper and a lower level and enhances the energy level of Ge s Sb s Te p_z/Ge p_z Sb p_z Te s states. Consequently, the sign of parity changes by inversing the characterizations of conduction band minimum and valence band maximum in a certain range of pressures. Moreover, the surface band structure with the Dirac cone feature was observed. The present results suggest that GST-related materials are a new family of pressure-induced topological insulators.