  Moire superlattices in van der Waals (vdW) heterostructures could trap
strongly bonded and long lived interlayer excitons. Assumed to be localized,
these moire excitons could form ordered quantum dot arrays, paving the way for
novel optoelectronic and quantum information applications. Here we perform
first principles simulations to shed light on moire excitons in twisted
MoS2/WS2 heterostructures. We provide the direct evidence of localized
interlayer moire excitons in vdW heterostructures. The moire potentials are
mapped out based on spatial modulations of energy gaps. Nearly flat valence
bands are observed in the heterostructures without magic angles. The dependence
of spatial localization and binding energy of the moire excitons on the twist
angle of the heterostructures is examined. We explore how electric field can be
tuned to control the position, polarity, emission energy, and hybridization
strength of the moire excitons. We predict that alternating electric fields
could modulate the dipole moments of hybridized moire excitons and suppress
their diffusion in Moire lattices.
