Remarkably Deep Moire Potential for Intralayer Excitons in MoSe2/MoS2 Twisted Heterobilayers

A moire superlattice formed in twisted van der Waals bilayers has emerged as a new tuning knob for creating new electronic states in two-dimensional materials. Excitonic properties can also be altered drastically due to the presence of moire potential. However, quantifying the moire potential for excitons is nontrivial. By creating a large ensemble of MoSe2/MoS2 heterobilayers with a systematic variation of twist angles, we map out the minibands of interlayer and intralayer excitons as a function of twist angles, from which we determine the moire potential for excitons. Surprisingly, the moire potential depth for intralayer excitons is up to similar to 130 meV, comparable to that for interlayer excitons. This result is markedly different from theoretical calculations based on density functional theory, which show an order of magnitude smaller moire potential for intralayer excitons. The remarkably deep intralayer moire potential is understood within the framework of structural reconstruction within the moire unit cell.