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

Abstract

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.

Large gap two-dimensional topological insulators with the coexistence of a significant Rashba effect and piezoelectricity in functionalized PbGe monolayers

“…The HSE06 functional was used to overcome the underestimation of bandgaps (PBE) and the calculated bandgaps are 0.418 and 0.405 eV, respectively. Their bandgap values are much larger than that of InTeO, 18 GaTeS and InTeS 19 mentioned above and greatly exceed the thermal broadening at room temperature. In addition, considering that the piezoelectric materials need a certain bandgap, the coexistence of QSH states with large bandgaps and piezoelectric properties makes PbGe(CN) 2 and PbGe(C 2 H) 2 potential candidate materials for low-power piezoelectric devices operating at room temperature.…”

“…On the other hand, considering that a single physical property is sometimes difficult to meet the needs of practical appli-cations, 2D multifunctional materials that combine QSH states and other physical properties, such as piezoelectricity, 18,19 ferroelectricity 20 and ferroelasticity, 21 are becoming a research hotspot in 2D topological materials. The coexistence of piezoelectricity and QSH states can bring a great breakthrough in the field of low-power piezoelectric devices.…”

“…18 GaTeS and InTeS monolayers (0.132 eV) were also reported to be PQSHIs. 19 However, small bandgaps may increase the risk of thermal excitation. In view of this, PQSHIs with larger bandgaps need to be further explored.…”