Fractional high-Chern insulator in twisted rhombohedral graphene.

Li, Zexu; Wang, Wenxuan; Wang, Fajie; Zhang, Zaizhe; Yang, Qiu; Watanabe, Kenji; Taniguchi, Takashi; Xie, X C et al. · Nature · 2026

basic_science · Level V

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Abstract

The realization of fractional Chern insulators opens the possibility of exploring fractionally charged excitations<sup>1-7</sup> and anyonic statistics<sup>8-11</sup> in the absence of a magnetic field. A central question is whether lattice-based systems can give rise to radically new states, distinct from those observed in traditional fractional quantum Hall systems<sup>12-20</sup>. Here we investigate a type of moiré flat-band system composed of Bernal bilayer graphene and rhombohedral tetralayer graphene. We discover an unprecedented richness of quantum anomalous Hall insulators with Chern numbers from |C| = 1 to |C| = 7 at a moiré filling factor v = 1 and around v = 3. Remarkably, we observe an exotic fractional Chern insulator with C = 7/3 around v = 2/3, which is beyond all known fractional Chern insulators described by either the Jain sequence or current high-Chern theory<sup>21-27</sup>. Our work expands the understanding of fractionally charged excitations beyond the Landau-level basis and offers a moiré platform for exploring anyons.