Realistic tight-binding model for monolayer transition metal dichalcogenides of 1T' structure

摘要

Monolayer transition metal dichalcogenides MX_2 (M = Mo, W and X = Te, Se, S) in 1T' structure were predicted to be quantum spin Hall insulators based on first-principles calculations, which were quickly confirmed by multiple experimental groups. For a better understanding of their properties, in particular, their responses to external fields, we construct a realistic four-band tight-binding (TB) model by combining the symmetry analysis and first-principles calculations. Our TB model respects all symmetries and can accurately reproduce the band structure in a large energy window from -0.3 eV to 0.8 eV. With the inclusion of spin-orbital coupling (SOC), our TB model can characterize the nontrivial topology and the corresponding edge states. Our TB model can also capture the anisotropic strain effects on the band structure and the strain-induced metal-insulator transition. Moreover, we found that although MX_2 share the same crystal structures and have the same crystal symmetries, the orbital composition of states around the Fermi level are qualitatively different and their lower-energy properties cannot be fully described by a single k · p model. Thus, we construct two different types of k·p models, one for MS_2 and MSe_2, the other for MTe_2, respectively. Benefiting from high accuracy and simplicity, our TB and k · p models can serve as a solid and concrete starting point for future studies of transport, superconductivity, strong correlation effects, and twistronics in 1T' transition metal dichalcogenides.