Influence of hydrostatic pressure and concentration of Ge on the topological band order of SnSi1-xGex alloys

Abstract

(Si, Ge, Sn)-based alloys are generally compatible with silicon technology and offer many options to engineer the optical properties. Furthermore, topological phases in some of these alloys have been investigated. In this work, through the calculations of the first-principles, the possibility of realization of topological phases in new SnSi1-xGex alloys (x = 0.0, 0.25, 0.5, 0.75, and 1.0) by hydrostatic pressure has been investigated. Furthermore, the effects of Ge concentration and the hydrostatic pressure on the topological phase of these alloys are studied and the band inversion strength (BIS) as a function of concentration (x) and pressure is plotted in a matrix image. The calculations of electronic band structure and band inversion of these alloys within two generalized gradient approximation (GGA) and Heyd-Scuseria-Ernzerhof screened hybrid (HSE06) functional are compared. It was found that the HSE06 approach was more effective than the GGA approach in improving bandgap and BIS. The results show that the nontrivial topological phase of these alloys in both approaches is due to an s-p band inversion at the Gamma (G) point. Moreover, the calculated topological surface states and ℤ2-index confirm the topological phase transition in these alloys. According to the HSE06 approach, at x ≤ 0.5, pressure changes play an essential role in the topological phase transition, while at x > 0.5, pressure changes affect only the BIS. The SnSi1-xGex alloys are dynamically stable, and it is expected that these alloys can be experimentally synthesized. © 2022 Elsevier B.V.