First-principles investigation of possible room-temperature topological insulators in monolayers

A Quantum Spin Hall (QSH) insulator with a large bulk band gap and tunable topological properties is crucial for both fundamental research and practical application. Chemical function-alization has been proposed as an effective route to realize the QSH effect. Using the ABINIT package, we have investigated the properties of (1) TlP, the functionalized monolayers TlPX(2) (X = F, Cl, Br, I); (2) TlAs, the functionalized monolayers TlAsX(2) (X = F, Cl, Br, I), and (3) GaGeTe, InGeTe, and InSnTe systems. The topological nature is verified by the calculation of the Z(2) topo-logical invariant. We discovered TlPF(2), TlPCl(2), TlPBr(2), TlPI(2), TlAs, TlAsF(2), TlAsCl(2), TlAsBr(2), and TlAsI(2) were promising 2D TIs with bulk band gaps as large as 0.21 eV. Each monolayer was suitable for room-temperature application, and show great potential for their future applications in quantum computers, nanoelectronics, and spintronics.