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arXiv · 2605.11794

Exciton-roton mode in moir\'e fractional Chern insulators

Xiaoyang Shen·Zijian Zhou·Ruiping Guo·Renqi Wang·Wenhui Duan·Chong Wang·Yong Xu
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Abstract

Moir\'e fractional Chern insulators (FCIs) are a novel class of quantum matter that realizes fractional quantum Hall (FQH) physics in zero magnetic field and provides a platform for exploring unconventional collective excitations. Here we show that hybridization between the magneto-roton and moir\'e interband excitations gives rise to an exciton-roton mode absent in continuum FQH systems in the long-wavelength limit. Using exact diagonalization and a variational Bethe-Salpeter equation for twisted MoTe$_2$, we demonstrate that this hybridization is controlled by the quantum geometry and yields a mode that combines excitonic optical response with the characteristic FCI roton minimum. The resulting exciton-roton remains low-lying, with excitation energy below the interband transition, and acquires optical activity, leading to a double-peak spectroscopic signature. These results identify optical spectroscopy as a direct probe of collective excitations in moir\'e FCIs.

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Xiaoyang Shen, Zijian Zhou, Ruiping Guo, Renqi Wang, Wenhui Duan, Chong Wang, Yong Xu. 2026-05-12. Exciton-roton mode in moir\'e fractional Chern insulators. https://arxiv.org/abs/2605.11794

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