Excitonic response in TMD heterostructures from first-principles: impact of stacking, twisting, and interlayer distance
Abstract
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 hetero-bilayers with different stacking and twisting. We analyse the valley splitting and optical transitions, and explain the enhancement or quenching of the inter- and intra-layer exciton states. Contrary to established models, that focus on transitions near the high-symmetry point K, our results include all possible transitions across the Brillouin Zone. This result, for a twisted Se-based heterostructures, in an interlayer exciton with significant electron density in both layers and a mixed intralayer exciton distributed over both MoSe2 and WSe2. 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 of the exciton peak positions (100 meV) and the exciton radiative lifetimes, from pico- to nano-seconds, and even micro-seconds in twisted bilayers. The control of exciton energies and lifetimes paves the way towards applications in quantum information technologies and optical sensing.
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