Electronic Properties of Monolayer 1T'-WTe2

Quantum spin Hall (QSH) insulators are promising candidate for electronic applications, for their time reversal protected back scattering-free edge states, with a pair of counter propagating, helical electronic modes. Transport experiment has shown monolayer 1T'-WTe2 displaying QS Hedge modes persisting up to 100 K. Here we present a 4-orbital tight-binding (TB) model for describing the low-energy physics of monolayer WTe2in 1T’ structure. Based on the symmetries analysis and first-principles calculations, 𝑑 𝑦-type orbitals from 2 Matoms and 𝑝𝑧-type or𝑝 -type orbitals from 2 out of the 4 X atoms are chosen as the basis. Hopping parameters of the TB model are fitted according to band structure calculated in the density functional theory (DFT) framework. The TB model includes all the hopping within nearest neighbor unit cells. It is able to well reproduce the energy bands −0.3~+0.75 eV around Fermi energy. Edge states for 4 different cuts of nanoribbon along the glide mirror preserving direction are calculated with Green’s function method, which confirms the nontrivial Z2 topological phases. The model is easily tunable to capture both semi-metallic and full gapped scenarios, based on the idea of applying strain on one direction. The TB models developed here is sufficient to describe the low-energy physics in monolayers 1T'-WTe2, and they can serve as basis for further study for their simplicity and high accuracy. The TB model here can be also easily applied for other monolayer1T’ transitional metal dichalcogenides MX2 (M=W, Mo; X=S, Se, Te).