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<p>Twisted bilayers of two-dimensional materials have emerged as a highly tunable platform to study and engineer properties of excitons. However, the atomistic description of these properties has remained a significant challenge as a consequence of the large unit cells of the emergent moiré superlattices. To address this problem, we introduce an efficient atomistic quantum-mechanical approach to solve the Bethe–Salpeter equation that exploits the localization of atomic Wannier functions. We then use this approach to study intra- and interlayer excitons in twisted WS<sub>2</sub>/WSe<sub>2</sub> at a range of twist angles. In agreement with experiment, we find that the optical spectrum exhibits three low-energy peaks for twist angles smaller than 2<sup>∘</sup>. The energy splitting between the peaks is described accurately. We also find two low-energy interlayer excitons with weak oscillator strengths. Our approach opens up new opportunities for the atomistic design of light-matter interactions in ultrathin materials.</p>

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Atomistic theory of twist-angle dependent intralayer and interlayer exciton properties in twisted bilayer materials

  • 期刊论文

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  • 发表日期：

    2025年3月4日

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  • Indrajit Maity,
  • Arash A. Mostofi,
  • Johannes Lischner

摘要

Twisted bilayers of two-dimensional materials have emerged as a highly tunable platform to study and engineer properties of excitons. However, the atomistic description of these properties has remained a significant challenge as a consequence of the large unit cells of the emergent moiré superlattices. To address this problem, we introduce an efficient atomistic quantum-mechanical approach to solve the Bethe–Salpeter equation that exploits the localization of atomic Wannier functions. We then use this approach to study intra- and interlayer excitons in twisted WS2/WSe2 at a range of twist angles. In agreement with experiment, we find that the optical spectrum exhibits three low-energy peaks for twist angles smaller than 2∘. The energy splitting between the peaks is described accurately. We also find two low-energy interlayer excitons with weak oscillator strengths. Our approach opens up new opportunities for the atomistic design of light-matter interactions in ultrathin materials.