Coexistence of the Piezoelectricity and Intrinsic Quantum-Spin Hall Effect in GaTeS and InTeS Monolayers: Implications for Spintronic Devices

Multifunctional two-dimensional (2D) nanomaterials play an increasingly dominant role in academic researches and practical applications. In this work, the coexistence of the piezoelectricity and intrinsic quantum-spin Hall (QSH) effect is predicted in MTeS (M = Ga and In) monolayers (d(11) = 3.988 pm V-1 for GaTeS and 8.687 pm V-1 for InTeS). When the Janus structure InGaTe2S2 is designed, the in-plane piezoelectric coefficient d(11) is enhanced to 10.512 pm V-1, with QSH state remaining. Meanwhile, an intriguing vertical piezoelectric polarization appears, which is attributed to breaking of the reflection symmetry. Moreover, their topological phases are robust and can exist in a wide range of uniaxial strains. In brief, coupling of the topology and piezoelectricity in MTeS (M = Ga and In) monolayers is promising to produce potential applications in piezoelectric quantum and nano spintronic devices.