Moiré Excitons in Van der Waals Heterostructures

Kha Tran, Galan Moody, Fengcheng Wu, Xiaobo Lu, Junho Choi, Akshay Singh, Jacob Embley, André Zepeda, Marshall Campbell, Kyounghwan Kim, Amritesh Rai, Travis Autry, Daniel A. Sanchez, Takashi Taniguchi, Kenji Watanabe, Nanshu Lu, Sanjay K. Banerjee, Emanuel Tutuc, Li Yang, Allan H. MacDonald, Kevin L. Silverman, Xiaoqin Li

Published 2018-07-10Version 1

In van der Waals (vdW) heterostructures formed by stacking two monolayer semiconductors, lattice mismatch or rotational misalignment introduces an in-plane moir\'e superlattice. While it is widely recognized that a moir\'e superlattice can modulate the electronic band structure and lead to novel transport properties including unconventional superconductivity and insulating behavior driven by correlations, its influence on optical properties has not been investigated experimentally. We present spectroscopic evidence that interlayer excitons are confined by the moir\'e potential in a high-quality MoSe2/WSe2 heterobilayer with small rotational twist. A series of interlayer exciton resonances with either positive or negative circularly polarized emission is observed in photoluminescence, consistent with multiple exciton states confined within the moir\'e potential. The recombination dynamics and temperature dependence of these interlayer exciton resonances are consistent with this interpretation. These results demonstrate the feasibility of engineering artificial excitonic crystals using vdW heterostructures for nanophotonics and quantum information applications.