Nature of novel moir\'e exciton states in WSe$_2$/WS$_2$ heterobilayers

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

arXiv · 2201.02562

Nature of novel moir\'e exciton states in WSe$_2$/WS$_2$ heterobilayers

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Abstract

Moir\'e patterns of transition metal dichalcogenide (TMD) heterobilayers have proven to be an ideal platform to host unusual correlated electronic phases, emerging magnetism, and correlated exciton physics. While the existence of novel moir\'e excitonic states is established 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-BSE calculations and micro-reflection spectroscopy, we identify the nature of the exciton resonances in WSe$_2$/WS$_2$ moir\'e superlattices, discovering a surprisingly rich set of moir\'e excitons that cannot be even qualitatively captured by prevailing continuum models. Our calculations reveal moir\'e excitons with distinct characters, including modulated Wannier excitons and previously unindentified intralayer charge-transfer excitons. Signatures of these distinct excitonic characters are confirmed experimentally via the unique carrier-density and magnetic-field dependences of different moir\'e exciton resonances. Our study highlights the highly non-trivial exciton states that can emerge in TMD moir\'e superlattices, and suggests novel ways of tuning many-body physics in moir\'e systems by engineering excited-states with specific spatial characters.

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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. 2022-01-07. Nature of novel moir\'e exciton states in WSe$_2$/WS$_2$ heterobilayers. https://arxiv.org/abs/2201.02562

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