Excitonic response in transition metal dichalcogenide heterostructures from first principles: Impact of stacking, twisting, and interlayer distance

Van der Waals heterostructures of two-dimensional transition metal dichalcogenides provide a unique platform to engineer optoelectronic devices tuning their optical properties via stacking, twisting, or straining. Using ab initio many-body perturbation theory, we predict the electronic and optical (absorption and photoluminescence spectra) properties of MoS2/WS2 and MoSe2/WSe2 heterobilayers with different stacking and twisting. We analyze the valley splitting and optical transitions, and we explain the enhancement or quenching of the inter- and intralayer exciton states. We fully include transitions within the entire Brillouin Zone, contrary to predictions based on continuum models which only consider energies near the K point. As a result, we predict an interlayer exciton with significant electron density in both layers and a mixed intralayer exciton distributed over both MoSe2 and WSe2 in a twisted Se-based heterostructure. We propose that it should be possible to produce an inverted order of the excitonic states in some MoSe2/WSe2 heterostructures, where the energy of the intralayer WSe2 exciton is lower than that in MoSe2. We predict the variability across different stacking of the exciton peak positions (∼100meV) and the exciton radiative lifetimes, from pico- to nanoseconds, and even microseconds in twisted bilayers. The control of exciton energies and lifetimes paves the way toward applications in quantum information technologies and optical sensing.