Transition metal dichalcogenide (TMDC) moir\'e superlattices, owing to the moir\'e flatbands and strong correlation, can host periodic electron crystals and fascinating correlated physics. The TMDC heterojunctions in the type-II alignment also enable long-lived interlayer excitons that are promising for correlated bosonic states, while the interaction is dictated by the asymmetry of the heterojunction. Here we demonstrate a new excitonic state, quadrupolar exciton, in a symmetric WSe2-WS2-WSe2 trilayer moir\'e superlattice. The quadrupolar excitons exhibit a quadratic dependence on the electric field, distinctively different from the linear Stark shift of the dipolar excitons in heterobilayers. This quadrupolar exciton stems from the hybridization of WSe2 valence moir\'e flatbands. The same mechanism also gives rise to an interlayer Mott insulator state, in which the two WSe2 layers share one hole laterally confined in one moir\'e unit cell. In contrast, the hole occupation probability in each layer can be continuously tuned via an out-of-plane electric field, reaching 100% in the top or bottom WSe2 under a large electric field, accompanying the transition from quadrupolar excitons to dipolar excitons. Our work demonstrates a trilayer moir\'e system as a new exciting playground for realizing novel correlated states and engineering quantum phase transitions.
@article{arxiv.2308.03219,
title = {Quadrupolar Excitons and Hybridized Interlayer Mott Insulator in a Trilayer Moir\'e Superlattice},
author = {Zhen Lian and Dongxue Chen and Lei Ma and Yuze Meng and Ying Su and Li Yan and Xiong Huang and Qiran Wu and Xinyue Chen and Mark Blei and Takashi Taniguchi and Kenji Watanabe and Sefaattin Tongay and Chuanwei Zhang and Yong-Tao Cui and Su-Fei Shi},
journal= {arXiv preprint arXiv:2308.03219},
year = {2023}
}