Large bandgap quantum spin hall insulator in methyl decorated plumbene monolayers

Abstract

Topologically protected edge states of quantum spin Hall (QSH) insulators have paved the way for dissipationless transport. In this regard, one of the key challenges is to find suitable QSH insulators with large bandgaps. Group IV analogues of graphene such as silicene, germanene, stanene, plumbene etc. are promising materials for QSH insulators due to their high spin-orbit coupling (SOC). Large bandgap opening may be possible in these group IV graphene analogues by chemical decoration. However, finding suitable chemical groups for such decoration has always been a demanding task. In this work, we investigate the performance of plumbene monolayer with –CX3 (X=H, F, Cl) chemical decoration and report very large bandgaps in the range of 0.8414 eV to 0.9818 eV with spin-orbit coupling, which is much higher compared to most other topological insulators and realizable at room temperature. The thermodynamic and electronic stabilities are calculated from phonon dispersion curve and quantum molecular dynamics simulation. The Z_2 topological invariants of the samples are calculated to confirm their topologically nontrivial property. The existence of edge states and topological nontrivial property are illustrated by investigating PbCX3 nanoribbons with zigzag edges. Lastly, the change of structural and electronic properties of the topological materials with strain are demonstrated to extend the scope of using these materials. Our findings suggest that these derivatives are promising materials for spintronic and future high performance nanoelectronic devices.