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Evidence for moiré excitons in van der Waals heterostructures

Published

Author(s)

Kha Tran, Galan Moody, Travis M. Autry, Kevin L. Silverman, Fengcheng Wu, Junho Choi, Akshay Singh, Jacob Embley, Andre Zepeda, Marshall Cambel, Kyoung Kim, Amritesh Rai, Daniel Sanchez, Takashi Taniguchi, Kenji Watanabe, Li Yang, Nanshu Lu, Sanjay Banerjee, emanuel tutuc, Allan H. MacDonald, Xiaoqin Li

Abstract

Recent advances in the isolation and stacking of monolayers of van der Waals materials have provided approaches for the preparation of quantum materials in the ultimate two-dimensional limit. In van der Waals heterostructures formed by stacking two monolayer semiconductors, lattice mismatch or rotational misalignment introduces an in-plane moiré superlattice. It is widely recognized that the moiré superlattice can modulate the electronic band structure of the material and lead to transport properties such as unconventional superconductivity and insulating behaviour driven by correlations; however, the influence of the moiré superlattice on optical properties has not been investigated experimentally. Here we report the observation of multiple interlayer exciton resonances with either positive or negative circularly polarized emission in a molybdenum diselenide/tungsten diselenide (MoSe2/WSe2) heterobilayer with a small twist angle. We attribute these resonances to excitonic ground and excited states confined within the moiré potential. This interpretation is supported by recombination dynamics and by the dependence of these interlayer exciton resonances on twist angle and temperature. These results suggest the feasibility of engineering artificial excitonic crystals using van der Waals heterostructures for nanophotonics and quantum information applications.
Citation
Nature
Volume
567

Keywords

2D materials, quantum confinement, exciton, spectroscopy
Created February 25, 2019, Updated July 9, 2019