Intrinsic edge excitons in two-dimensional MoS$_2$

TL;DR

This paper predicts the existence of intrinsic edge excitons in two-dimensional MoS$_2$, which are robust, have large binding energies, and are likely common in similar transition-metal dichalcogenides, based on first-principles calculations.

Contribution

It introduces the prediction of universal, intrinsic edge excitons in 2D MoS$_2$ using advanced many-body perturbation theory, highlighting their robustness and potential universality.

Findings

Edge excitons are well below bulk features.

Excitons are insensitive to edge terminations and orientation.

Large binding energies of ~0.4 eV are observed.

Abstract

Using accurate first-principles calculations based on many-body perturbation theory we predict that two-dimensional MoS$_2$ hosts edge excitons with universal character, intrinsic to the existence of edges and lying well below the onset of bulk features. These excitons are largely insensitive to edge terminations or orientation, persisting even in the presence of metallic screening at zigzag edges, with large binding energies of $\sim$0.4 eV. Additional excitons can also emerge in ultranarrow ribbons, or as a function of the chemical nature of the termination. The chemical, structural, and electronic similarities with Se- or W-based transition-metal dichalcogenides suggest that these optical features could be common in this class of materials.