Self-organized quantum dots in marginally twisted MoSe2/WSe2 and MoS2/WS2 bilayers
V. V. Enaldiev, F. Ferreira, James G. McHugh, Vladimir I. Fal’ko
Abstract
Abstract Moiré superlattices in twistronic heterostructures are a powerful tool for materials engineering. In marginally twisted (small misalignment angle, θ ) bilayers of nearly lattice-matched two-dimensional (2D) crystals moiré patterns take the form of domains of commensurate stacking, separated by a network of domain walls (NoDW) with strain hot spots at the NoDW nodes. Here, we show that, for type-II transition metal dichalcogenide bilayers MoX 2 /WX 2 (X=S, Se), the hydrostatic strain component in these hot spots creates quantum dots for electrons and holes. We investigate the electron/hole states bound by such objects, discussing their manifestations via the intralayer intraband infrared transitions. The electron/hole confinement, which is strongest for θ < 0.5°, leads to a red-shift of their recombination line producing single-photon emitters (SPE) broadly tuneable around 1 eV by misalignment angle. These self-organized dots can form in bilayers with both aligned and inverted MoX 2 and WX 2 unit cells, emitting photons with different polarizations. We also find that the hot spots of strain reduce the intralayer MoX 2 A-exciton energy, enabling selective population of the quantum dot states.