Odd-Chern-Number Quantum Anomalous Hall Effect at Even Filling in Moire Rhombohedral Heptalayer Graphene

Quantum anomalous Hall effect (QAHE) in graphene moiré superlattices has drawn considerable and sustained attention, owing to both fundamental interests of Chern insulators and promising applications in topological electronics. An empirical regularity suggests that QAHE manifests exclusively at odd-electron filling per moiré unit cell, whereas even-filling configurations-particularly at half-filled bands-invariably yield topologically trivial insulators. This dichotomy, originating from quantum states competition, has been the key issue in theoretical investigations of topology and correlation, but its universality remains an open question. Here we demonstrate a violation of this paradigm in rhombohedral heptalayer graphene/hexagonal boron nitride moiré superlattices, where a robust Chern insulator emerges at two-electron filling per moiré unit cell. It wins the competition with a trivial correlated insulator only above a critical displacement field as large as ∼1  V/nm. The odd Chern number C=1 for the filling of 2 is intriguing: theoretical calculation shows that electrons occupy two interaction-renormalized bands with distinct spin-valley flavors, whose charge densities arrange into dual honeycomb and triangular lattices, leading to a total Chern number of 1 and minimized Coulomb repulsion. Our findings broaden the landscape for engineering nontrivial topological states, while providing critical insights into the delicate competition between emergent quantum phases in strongly correlated moiré systems.