Electronic excitations in transition metal dichalcogenide monolayers from an LDA plus GdW approach

Monolayers of transition metal dichalcogenides (TMDCs) have unique optoelectronic properties. Density functional theory allows only for a limited description of the electronic excitation energies in these systems, while a more advanced treatment within many-body perturbation theory employing the GW/BSE approximation is often rather time consuming. Here, we show that the recently developed LDA+GdW approach provides an efficient and at the same time reliable description of one-particle energies, as well as optical properties including bound excitons in TMDCs. For five exemplary materials (MoSe₂, MoS₂, WSe₂, WS₂, and ReSe₂), we discuss the numerical convergence, in particular with respect to k-point sampling, and show that the GdW/BSE approximation gives results similar to common GW/BSE calculations. Such efficient approaches are essential to treat larger multilayer systems or defects.