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.