Influence of the effective layer thickness on the ground-state and excitonic properties of transition-metal dichalcogenide systems

A self-consistent scheme for the calculations of the interacting ground state and the near band-gap optical spectra of mono- and multilayer transition-metal-dichalcogenide systems is presented. The approach combines a dielectric model for the Coulomb interaction potential in a multilayer environment, gap equations for the renormalized ground state, and the Dirac-Wannier equation to determine the excitonic properties. To account for the extension of the individual monolayers perpendicular to their basic plane, an effective thickness parameter in the Coulomb interaction potential is introduced. Numerical evaluations show that the resulting finite thickness effects lead to significant modifications in the optical spectra, reproducing the experimentally observed nonhydrogenic features of the excitonic resonance series. Applying the theory for a variety of experimentally relevant configurations, a consistent description of the near band-gap optical properties is obtained all the way from monolayer to bulk. In addition to the well-known in-plane excitons, also interlayer excitons occur in multilayer systems suggesting a reinterpretation of experimental results obtained for bulk material.