Intralayer charge-transfer moiré excitons in van der Waals superlattices

Mit H Naik; Emma C Regan; Zuocheng Zhang; Yang-Hao Chan; Zhenglu Li; Danqing Wang; Yoseob Yoon; Chin Shen Ong; Wenyu Zhao; Sihan Zhao; M Iqbal Bakti Utama; Beini Gao; Xin Wei; Mohammed Sayyad; Kentaro Yumigeta; Kenji Watanabe; Takashi Taniguchi; Sefaattin Tongay; Felipe H da Jornada; Feng Wang; Steven G Louie

doi:10.1038/s41586-022-04991-9

Intralayer charge-transfer moiré excitons in van der Waals superlattices

Nature. 2022 Sep;609(7925):52-57. doi: 10.1038/s41586-022-04991-9. Epub 2022 Aug 31.

Authors

Mit H Naik^#^{1

2}, Emma C Regan^#^{1

2

3}, Zuocheng Zhang^#¹, Yang-Hao Chan^{1

2

4}, Zhenglu Li^{1

2}, Danqing Wang^{1

3}, Yoseob Yoon^{1

2}, Chin Shen Ong^{1

2}, Wenyu Zhao¹, Sihan Zhao⁵, M Iqbal Bakti Utama^{1

2

6}, Beini Gao¹, Xin Wei¹, Mohammed Sayyad⁷, Kentaro Yumigeta⁶, Kenji Watanabe^{8

9}, Takashi Taniguchi^{8

9}, Sefaattin Tongay⁷, Felipe H da Jornada¹⁰, Feng Wang^{1

2

11}, Steven G Louie^{12

13}

Affiliations

¹ Department of Physics, University of California at Berkeley, Berkeley, CA, USA.
² Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
³ Graduate Group in Applied Science and Technology, University of California at Berkeley, Berkeley, CA, USA.
⁴ Institute of Atomic and Molecular Sciences, Academia Sinica and Physics Division, National Center for Theoretical Sciences, Taipei, Taiwan.
⁵ Interdisciplinary Center for Quantum Information, Zhejiang Province Key Laboratory of Quantum Technology and Device, State Key Laboratory of Silicon Materials, and Department of Physics, Zhejiang University, Hangzhou, China.
⁶ Department of Materials Science and Engineering, University of California at Berkeley, Berkeley, CA, USA.
⁷ School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ, USA.
⁸ Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan.
⁹ International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan.
¹⁰ Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA.
¹¹ Kavli Energy NanoSciences Institute at University of California Berkeley and Lawrence, Berkeley National Laboratory, Berkeley, CA, USA.
¹² Department of Physics, University of California at Berkeley, Berkeley, CA, USA. sglouie@berkeley.edu.
¹³ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. sglouie@berkeley.edu.

^# Contributed equally.

PMID: 36045239
DOI: 10.1038/s41586-022-04991-9

Abstract

Moiré patterns of transition metal dichalcogenide heterobilayers have proved to be an ideal platform on which to host unusual correlated electronic phases, emerging magnetism and correlated exciton physics. Whereas the existence of new moiré excitonic states is established^1-4 through optical measurements, the microscopic nature of these states is still poorly understood, often relying on empirically fit models. Here, combining large-scale first-principles GW (where G and W denote the one-particle Green's function and the screened Coulomb interaction, respectively) plus Bethe-Salpeter calculations and micro-reflection spectroscopy, we identify the nature of the exciton resonances in WSe₂/WS₂ moiré superlattices, discovering a rich set of moiré excitons that cannot be captured by prevailing continuum models. Our calculations show moiré excitons with distinct characters, including modulated Wannier excitons and previously unidentified intralayer charge-transfer excitons. Signatures of these distinct excitonic characters are confirmed experimentally by the unique carrier-density and magnetic-field dependences of different moiré exciton resonances. Our study highlights the highly non-trivial exciton states that can emerge in transition metal dichalcogenide moiré superlattices, and suggests new ways of tuning many-body physics in moiré systems by engineering excited-states with specific spatial characters.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.