The realization of fractional Chern insulators opens the possibility of exploring fractionally charged excitations1–7 and anyonic statistics8–11 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 systems12–20. 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 theory21–27. Our work expands the understanding of fractionally charged excitations beyond the Landau-level basis and offers a moiré platform for exploring anyons. A rich variety of both integer and fractional high-Chern insulators are observed in a moiré system composed of Bernal bilayer graphene and rhombohedral tetralayer graphene.
Extended Data Fig. 1 Structural characterization and optical micrographs of TBRTG devices.
a, Optical micrographs showing the bilayer graphene and rhombohedral tetralayer graphene regions after laser etching for device D1, D2 and D3. b, Optical image... [7511 chars]