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Title: Identification of spin, valley and moiré quasi-angular momentum of interlayer excitons

Abstract

Moiré superlattices provide a powerful way to engineer properties of electrons and excitons in two-dimensional van der Waals heterostructures. The moir\'e effect can be especially strong for interlayer excitons, where electrons and holes reside in different layers and can be addressed separately. In particular, it was recently proposed that the moiré superlattice potential not only localizes interlayer exciton states at different superlattice positions, but also hosts an emerging moiré quasi-angular momentum (QAM) that periodically switches the optical selection rules for interlayer excitons at different moiré sites. Here we report the observation of multiple interlayer exciton states coexisting in a WSe 2/WS 2 moiré superlattice and unambiguously determine their spin, valley, and moiré QAM through novel resonant optical pump-probe spectroscopy and photoluminescence excitation spectroscopy. We demonstrate that interlayer excitons localized at different moiré sites can exhibit opposite optical selection rules due to the spatially-varying moiré QAM. Finally, our observation reveals new opportunities to engineer interlayer exciton states and valley physics with moiré superlattices for optoelectronic and valleytronic applications.

Authors:
 [1];  [1];  [1];  [1];  [2];  [3];  [4];  [4];  [1];  [5];  [5];  [4];  [3];  [3]
  1. Univ. of California, Berkeley, CA (United States)
  2. Univ. of California, Berkeley, CA (United States); National Taiwan Normal Univ., Taipei (Taiwan)
  3. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kavli Energy NanoScience Institute, Berkeley, CA (United States)
  4. Arizona State Univ., Tempe, AZ (United States)
  5. National Inst. for Materials Science, Tsukuba (Japan)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; US Army Research Office (ARO); Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan; National Science Foundation (NSF); USDOD
OSTI Identifier:
1604679
Grant/Contract Number:  
AC02-05CH11231; W911-NF-17-1-0312; JP15K21722; 107-2112-M-003-014-MY3
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nature Physics
Additional Journal Information:
Journal Volume: 15; Journal Issue: 11; Journal ID: ISSN 1745-2473
Publisher:
Nature Publishing Group (NPG)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; condensed-matter physics; optical materials and strucutres; two-dimensional materials

Citation Formats

Jin, Chenhao, Regan, Emma C, Wang, Danqing, Utama, M Iqbal Bakti, Yang, Chan-Shan, Cain, Jeffrey, Qin, Ying, Shen, Yuxia, Zheng, Zhiren, Watanabe, Kenji, Taniguchi, Takashi, Tongay, Sefaattin, Zettl, Alex, and Wang, Feng. Identification of spin, valley and moiré quasi-angular momentum of interlayer excitons. United States: N. p., 2019. Web. doi:10.1038/s41567-019-0631-4.
Jin, Chenhao, Regan, Emma C, Wang, Danqing, Utama, M Iqbal Bakti, Yang, Chan-Shan, Cain, Jeffrey, Qin, Ying, Shen, Yuxia, Zheng, Zhiren, Watanabe, Kenji, Taniguchi, Takashi, Tongay, Sefaattin, Zettl, Alex, & Wang, Feng. Identification of spin, valley and moiré quasi-angular momentum of interlayer excitons. United States. doi:10.1038/s41567-019-0631-4.
Jin, Chenhao, Regan, Emma C, Wang, Danqing, Utama, M Iqbal Bakti, Yang, Chan-Shan, Cain, Jeffrey, Qin, Ying, Shen, Yuxia, Zheng, Zhiren, Watanabe, Kenji, Taniguchi, Takashi, Tongay, Sefaattin, Zettl, Alex, and Wang, Feng. Mon . "Identification of spin, valley and moiré quasi-angular momentum of interlayer excitons". United States. doi:10.1038/s41567-019-0631-4. https://www.osti.gov/servlets/purl/1604679.
@article{osti_1604679,
title = {Identification of spin, valley and moiré quasi-angular momentum of interlayer excitons},
author = {Jin, Chenhao and Regan, Emma C and Wang, Danqing and Utama, M Iqbal Bakti and Yang, Chan-Shan and Cain, Jeffrey and Qin, Ying and Shen, Yuxia and Zheng, Zhiren and Watanabe, Kenji and Taniguchi, Takashi and Tongay, Sefaattin and Zettl, Alex and Wang, Feng},
abstractNote = {Moiré superlattices provide a powerful way to engineer properties of electrons and excitons in two-dimensional van der Waals heterostructures. The moir\'e effect can be especially strong for interlayer excitons, where electrons and holes reside in different layers and can be addressed separately. In particular, it was recently proposed that the moiré superlattice potential not only localizes interlayer exciton states at different superlattice positions, but also hosts an emerging moiré quasi-angular momentum (QAM) that periodically switches the optical selection rules for interlayer excitons at different moiré sites. Here we report the observation of multiple interlayer exciton states coexisting in a WSe2/WS2 moiré superlattice and unambiguously determine their spin, valley, and moiré QAM through novel resonant optical pump-probe spectroscopy and photoluminescence excitation spectroscopy. We demonstrate that interlayer excitons localized at different moiré sites can exhibit opposite optical selection rules due to the spatially-varying moiré QAM. Finally, our observation reveals new opportunities to engineer interlayer exciton states and valley physics with moiré superlattices for optoelectronic and valleytronic applications.},
doi = {10.1038/s41567-019-0631-4},
journal = {Nature Physics},
issn = {1745-2473},
number = 11,
volume = 15,
place = {United States},
year = {2019},
month = {8}
}

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