Flavor-Polarized Chern Insulator in the Half-Filled Rhombohedral Graphene Moiré Superlattice

Graphene-based moiré superlattices exhibit novel quantum phenomena driven by pronounced interactions, leading to topological correlated states like orbital Chern insulators exhibiting quantum anomalous Hall effects. Typically, intrinsic Chern insulators are stabilized at odd moiré fillings, as even fillings often result in valley-balanced, topologically trivial states at zero magnetic field. In this Letter, we report the observation of a Chern insulator with C=1 state at moiré filling ν=2 in the rhombohedral octalayer graphene/hexagonal boron nitride moiré superlattice. In the vicinity of this topological phase, we also observe a robust topologically trivial correlated insulator at the same filling, highlighting the intense competition between different ground states. Observing such a Chern insulator, in particular with C=1 at ν=2 is intriguing, as the lowest moiré band in each flavor is expected to host Chern number C=1 or -1. We further demonstrate that such a state could originate from the hybridization between the low-energy moiré flat bands and high-energy remote bands in a single flavor by self-consistent Hartree-Fock calculation. Our findings extend the known topological phase diagram of rhombohedral multilayer graphene moiré systems and establish this platform as highly promising for investigating strong electron correlations and multiband hybridized transport at fillings higher than ν=1.