Pressure-induced topological phase transitions in rocksalt chalcogenides

By means of a comprehensive theoretical investigation, we show that external pressure can induce topological phase transitions in IV-VI semiconducting chalcogenides with a rocksalt structure. These materials satisfy mirror symmetries that are needed to sustain topologically protected surface states, at variance with time-reversal symmetry that is responsible for gapless edge states in Z2 topological insulators. The band inversions at high-symmetry points in the Brillouin zone that are related by mirror symmetry are brought about by an "asymmetric" hybridization between cation and anion sp orbitals. By working out the microscopic conditions to be fulfilled in order to maximize this hybridization, we identify materials in the rocksalt chalcogenide class that are prone to undergo a topological phase transition induced by pressure and/or alloying. Our model analysis is fully confirmed by complementary advanced first-principles calculations and ab initio-based tight-binding simulations.