Local-field effects on the plasmon dispersion of two-dimensional transition metal dichalcogenides

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) are gaining increasing attention as an alternative to graphene for their very high potential in optoelectronics applications. Here, we consider two prototypical metallic 2D TMDs, NbSe₂ and TaS₂. Using a first-principles approach, we investigate the properties of the localized intraband d plasmon that cannot be modeled on the basis of the homogeneous electron gas. Finally, we discuss the effects of the reduced dimensionality on the plasmon dispersion through the interplay between the interband transitions and the local-field effects. This result can be exploited to tune the plasmonic properties of these novel 2D materials.