Spin-orbit-stable type-II nodal line band crossing in n-doped monolayer MoX2 (X=S,Se,Te)

TL;DR

This paper demonstrates that n-doped monolayer MoX2 (X=S, Se, Te) hosts a spin-orbit-stable type-II nodal line crossing in its conduction bands, due to mirror symmetry, expanding the understanding of 2D topological materials.

Contribution

It reveals the existence of a spin-orbit-stable type-II nodal line in monolayer MoX2 caused by mirror symmetry, which was not previously known.

Findings

N-doped monolayer MoX2 exhibits a type-II nodal line crossing.

The nodal line occurs along arbitrary directions due to mirror symmetry.

The band crossing is stable against spin-orbit coupling effects.

Abstract

1H-phase monolayer transition-metal dichalcogenides have spin-split electronic band structures near the K(K') point due to strong spin-orbit coupling and intrinsic inversion symmetry breaking. In case of the monolayer MoX2 (X=S, Se, Te), the spin-split conduction bands cross near the K(K') point. We show that the band crossing occurs not only along the high symmetry directions, but also along arbitrary directions due to a mirror reflection symmetry of the monolayer. As a result, n-doped monolayer MoX2 is a two-dimensional type-II nodal-line material.