Evidence of Moiré Excitons in van der Waal(vdW) Heterostructure*

We report spectroscopy evidence of interlayers excitons confined by a moire superlattice in hBN encapsulated MoSe₂/WSe₂ heterostructures with small twist angles. Low temperature photoluminescence(PL) measurement shows that interlayer exciton splits into multiple peaks with alternating circular polarization. We assign these peaks to the ground state and excited state excitons localized within a Moiré supercell and explain how the spatial variation of optical selection rule can give rise to multiple peaks with alternative circular polarization. Temperature dependence PL, twist angle dependence, and recombination dynamics all agrees with the localized exciton picture. Our results suggest the feasibility of engineering artificial excitonic crystal using vdW heterostructures for nanophotonics and quantum information applications.