Moiré trions in MoSe2/WSe2 heterobilayers

Xi Wang; Jiayi Zhu; Kyle L Seyler; Pasqual Rivera; Huiyuan Zheng; Yingqi Wang; Minhao He; Takashi Taniguchi; Kenji Watanabe; Jiaqiang Yan; David G Mandrus; Daniel R Gamelin; Wang Yao; Xiaodong Xu

doi:10.1038/s41565-021-00969-2

Moiré trions in MoSe₂/WSe₂ heterobilayers

Nat Nanotechnol. 2021 Nov;16(11):1208-1213. doi: 10.1038/s41565-021-00969-2. Epub 2021 Sep 16.

Authors

Xi Wang^#^{1

2}, Jiayi Zhu^#¹, Kyle L Seyler¹, Pasqual Rivera¹, Huiyuan Zheng^{3

4}, Yingqi Wang¹, Minhao He¹, Takashi Taniguchi⁵, Kenji Watanabe⁶, Jiaqiang Yan^{7

8}, David G Mandrus^{7

8

9}, Daniel R Gamelin², Wang Yao^{10

11}, Xiaodong Xu^{12

13}

Affiliations

¹ Department of Physics, University of Washington, Seattle, WA, USA.
² Department of Chemistry, University of Washington, Seattle, WA, USA.
³ Department of Physics, University of Hong Kong, Hong Kong, China.
⁴ HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong, Hong Kong, China.
⁵ International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan.
⁶ Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan.
⁷ Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
⁸ Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN, USA.
⁹ Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA.
¹⁰ Department of Physics, University of Hong Kong, Hong Kong, China. wangyao@hku.hk.
¹¹ HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong, Hong Kong, China. wangyao@hku.hk.
¹² Department of Physics, University of Washington, Seattle, WA, USA. xuxd@uw.edu.
¹³ Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA. xuxd@uw.edu.

^# Contributed equally.

PMID: 34531556
DOI: 10.1038/s41565-021-00969-2

Abstract

Transition metal dichalcogenide moiré bilayers with spatially periodic potentials have emerged as a highly tunable platform for studying both electronic^1-6 and excitonic^4,7-13 phenomena. The power of these systems lies in the combination of strong Coulomb interactions with the capability of controlling the charge number in a moiré potential trap. Electronically, exotic charge orders at both integer and fractional fillings have been discovered^2,5. However, the impact of charging effects on excitons trapped in moiré potentials is poorly understood. Here, we report the observation of moiré trions and their doping-dependent photoluminescence polarization in H-stacked MoSe₂/WSe₂ heterobilayers. We find that as moiré traps are filled with either electrons or holes, new sets of interlayer exciton photoluminescence peaks with narrow linewidths emerge about 7 meV below the energy of the neutral moiré excitons. Circularly polarized photoluminescence reveals switching from co-circular to cross-circular polarizations as moiré excitons go from being negatively charged and neutral to positively charged. This switching results from the competition between valley-flip and spin-flip energy relaxation pathways of photo-excited electrons during interlayer trion formation. Our results offer a starting point for engineering both bosonic and fermionic many-body effects based on moiré excitons¹⁴.