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

TL;DR

This paper develops a comprehensive four-band tight-binding model for monolayer 1T' transition metal dichalcogenides, accurately capturing their electronic structure, topology, and strain effects, serving as a foundation for future research.

Contribution

It introduces a realistic, symmetry-respecting tight-binding model that reproduces the band structure and topological features of 1T' TMDs, and constructs specialized k·p models for different material groups.

Findings

Accurately reproduces band structure from -0.3 eV to 0.8 eV

Characterizes nontrivial topology and edge states with SOC

Captures strain effects and metal-insulator transition

Abstract

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 the 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, while the orbital composition of states around the Fermi level are qualitatively different and their lower-energy properties cannot fully described by a single k $\cdot$ p model. Thus, we construct two different types of k $\cdot$ p model for $M$S$_2$,$M$Se$_2$ and $M$Te$_2$, respectively. Benefiting from the high accuracy and simplicity, our TB and k $\cdot$ 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.