Realization of a piezoelectric quantum spin Hall phase with a large band gap in MBiH (M = Ga and In) monolayers

Abstract

Piezoelectric quantum spin Hall insulators (PQSHIs), as a nascent field, can realize the coexistence of QSH states and piezoelectricity. However, diminutive topological band gap is the dominant obstacle to its practical applications. In order to solve this predicament, we design a new family of two-dimensional (2D) materials MBiH (M = Ga and In) monolayers and predict them to be intrinsic PQSHIs with largest QSH bandgap up to 0.735 eV. In addition, MBiH exhibits considerable piezoelectricity strain coefficients of 4.163 pm V⁻¹ and 5.415 pm V⁻¹ for GaBiH and InBiH, respectively, which are comparable to and even exceed those of many well-known piezoelectric materials, for example, α-quartz (d₁₁ = 2.31 pm V⁻¹) and MoS₂ (d₁₁ = 3.73 pm V⁻¹). Our results indicate that MBiH (M = Ga and In) has potential applications in low-power piezoelectric devices.