Effects of pressure and temperature on topological electronic materials X₂Y₃ (X = As, Sb, Bi; Y = Se, Te) using...

We systematically study the thermal and topological properties of X₂Y₃ (X = As, Sb, Bi; Y = Se, Te) and the effects of pressure and temperature on their electronic properties using first-principles. We find that the external pressure-induced electronic topological transition occurs at about 5 GPa for Bi₂Se₃, and the type of band gap tends to become indirect with the increase of pressure. We also investigate the lattice expansion with temperature in quasi-harmonic approximation and further explore the effect of temperature on the volume, band gap, and volumetric thermal expansion coefficient of the studied selenides and tellurides. Finally, we calculate the evolution of the Wannier charge center of X₂Y₃ to determine their topological invariants, and theoretically suggest that Bi₂Se₃ changes from a topological to an ordinary insulator when the pressure decreases to -8 GPa; As₂Se₃ is found to be an ordinary insulator, while all other four compounds are always strong topological insulators at any pressure or temperature.