Electronic properties and inter- and intralayer excitons in MoSe₂/ WSe₂ heterostructure

We describe the electronic and optical properties of MoSe₂ / WSe₂ heterostructure using a combination of density functional theory, tight-binding (TB) approximation and Bethe-Salpeter equation (BSE) for excitons. We start with determining the electronic structure of MoSe₂ / WSe₂ from first principles, using the PBE parametrization of the GGA for the exchange-correlation potentials and including spin-orbit interaction. We obtain type-II band alignment and conduction band minima at Q points in agreement with previous work. We include analysis of Kohn-Sham wavefunctions allowing to describe the leading layer and spin contribution for a given band. Following our previous work on monolayers we construct the ab initio based TB model [1] for MoSe₂ / WSe₂ heterostructure, which allows to understand orbital contributions to Bloch states and study of both twisted transition metal dichalcogenide (TMD) heterostructures and TMD-based multi-million atom nanostructures. To validate the model we compute the exciton spectrum using dielectrically modified Keldysz electron-hole interaction. We accurately solve BSE and determine the exciton fine structure due to type-II spin-split band arrangement and topological moments, considering both A/B, spin bright/dark and intra-/interlayer exciton series.