Robust topological insulating property in CX-functionalized III-V monolayers.

Two-dimensional topological insulators (TIs) show great potential applications in low-power quantum computing and spintronics due to the spin-polarized gapless edge states. However, the small bandgap limits their room-temperature applications. Based on first-principles calculations, a series of CX (X = H, F, Cl, Br and I) functionalized III-V monolayers are investigated. The nontrivial bandgaps of GaBi-(CX), InBi-(CX), TlBi-(CX)and TlSb-(CX)are found to between 0.223 and 0.807 eV. For GaBi-(CX)and InBi-(CX), the topological insulating properties originate from theband inversion induced by the spin-orbital coupling (SOC) effect. While for TlBi-(CX)and TlSb-(CX), the topological insulating properties are attributed to the SOC effect-induced band splitting. The robust topological characteristics are further confirmed by topological invariantsand the test under biaxial strain. Finally, two ideal substrates are predicted to promote the applications of these TIs. These findings indicate that GaBi-(CX), InBi-(CX), TlBi-(CX)and TlSb-(CX)monolayers are good candidates for the fabrication of spintronic devices.