Strain-Induced Quantum Spin Hall Effect in Two-Dimensional Methyl-Functionalized Silicene SiCH₃.

Quantum Spin Hall (QSH) has potential applications in low energy consuming spintronic devices and has become a researching hotspot recently. It benefits from insulators feature edge states, topologically protected from backscattering by time-reversal symmetry. The properties of methyl functionalized silicene (SiCH₃) have been investigated using first-principles calculations, which show QSH effect under reasonable strain.

Tunable Electronic and Topological Properties of Germanene by Functional Group Modification.

Electronic and topological properties of two-dimensional germanene modified by functional group X (X = H, F, OH, CH₃) at full coverage are studied with first-principles calculation. Without considering the effect of spin-orbit coupling (SOC), all functionalized configurations become semiconductors, removing the Dirac cone at K point in pristine germanene. We also find that their band gaps can be especially well tuned by an external strain.