Observation of Moiré Excitons in van der Waals Heterostructure*

Moire superlattice in van der Waals systems provide a powerful tool to engineer the properties of two-dimensional materials through introducing a new energy and length scale. For example, correlated insulating states and superconductivity have been reported in graphene systems, where the moiré superlattice qualitatively change the behavior of electrons. The effects of moiré superlattice on excitons, on the other hand, is less studies experimentally. Here we report the observation of moiré excitons in heterostructure of two-dimensional semiconductors, and show that the properties of excitons can also be strongly modified by a moiré superlattice.