Moiré enhanced flat band in rhombohedral graphene

Hongyun Zhang; Jinxi Lu; Kai Liu; Yijie Wang; Fei Wang; Size Wu; Wanying Chen; Xuanxi Cai; Kenji Watanabe; Takashi Taniguchi; Jose Avila; Pavel Dudin; Matthew D. Watson; Alex Louat; Takafumi Sato; Pu Yu; Wenhui Duan; Zhida Song; Guorui Chen; Shuyun Zhou

arXiv · 2504.06251

Moiré enhanced flat band in rhombohedral graphene

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Abstract

The fractional quantum anomalous Hall effect (FQAHE) is a fascinating emergent quantum state characterized by fractionally charged excitations in the absence of magnetic field,which could arise from the intricate interplay between electron correlation, nontrivial topology and spontaneous time-reversal symmetry breaking. Recently, FQAHE has been realized in aligned rhombohedral pentalayer graphene on BN superlattice (aligned R5G/BN), where the topological flat band is modulated by the moiré potential. However, intriguingly, the FQAHE is observed only when electrons are pushed away from the moiré interface. The apparently opposite implications from these experimental observations, along with different theoretical models, have sparked intense debates regarding the role of the moiré potential. Unambiguous experimental observation of the topological flat band as well as moiré bands with energy and momentum resolved information is therefore critical to elucidate the underlying mechanism. Here by performing nanospot angle-resolved photoemission spectroscopy (NanoARPES) measurements, we directly reveal the topological flat band electronic structures of R5G, from which key hopping parameters essential for determining the fundamental electronic structure of rhombohedral graphene are extracted. Moreover, a comparison of electronic structures between aligned and non-aligned samples reveals that the moiré potential plays a pivotal role in enhancing the topological flat band in the aligned sample. Our study provides experimental guiding lines to narrow down the phase space of rhombohedral graphene, laying an important foundation for understanding exotic quantum phenomena in this emerging platform.

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Hongyun Zhang, Jinxi Lu, Kai Liu, Yijie Wang, Fei Wang, Size Wu, Wanying Chen, Xuanxi Cai, Kenji Watanabe, Takashi Taniguchi, Jose Avila, Pavel Dudin, Matthew D. Watson, Alex Louat, Takafumi Sato, Pu Yu, Wenhui Duan, Zhida Song, Guorui Chen, Shuyun Zhou. 2025-04-08. Moiré enhanced flat band in rhombohedral graphene. https://arxiv.org/abs/2504.06251

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