Shedding light on moiré excitons: A first-principles perspective

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Science Advances  16 Oct 2020:
Vol. 6, no. 42, eabc5638
DOI: 10.1126/sciadv.abc5638


Moiré superlattices in van der Waals (vdW) heterostructures could trap long-lived interlayer excitons. These moiré excitons could form ordered quantum dot arrays, paving the way for unprecedented optoelectronic and quantum information applications. Here, we perform first-principles simulations to shed light on moiré excitons in twisted MoS2/WS2 heterostructures. We provide direct evidence of localized interlayer moiré excitons in vdW heterostructures. The interlayer and intralayer moiré potentials are mapped out based on spatial modulations of energy gaps. Nearly flat valence bands are observed in the heterostructures. The dependence of spatial localization and binding energy of the moiré excitons on the twist angle of the heterostructures is examined. We explore how vertical electric field can be tuned to control the position, polarity, emission energy, and hybridization strength of the moiré excitons. We predict that alternating electric fields could modulate the dipole moments of hybridized moiré excitons and suppress their diffusion in moiré lattices.

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