Chern Insulators at Integer and Fractional Filling in Moiré Pentalayer Graphene

Abstract

The advent of moiré platforms for engineered quantum matter has led to discoveries of integer and fractional quantum anomalous Hall effects, with predictions for correlation-driven topological states based on electron crystallization. Here, we report an array of trivial and topological insulators formed in a moiré lattice of rhomobohedral pentalayer graphene (R5G). At a doping of one electron per moiré unit cell (ν=1), we see a correlated insulator with a Chern number that can be tuned between C=0 and +1 by an electric displacement field. This is accompanied by a series of additional Chern insulators with C=+1 originating from fractional fillings of the moiré lattice—ν=1/4, 1/3, and 2/3—associated with the formation of moiré-driven topological electronic crystals. At ν=2/3 the system exhibits an integer quantum anomalous Hall effect at zero magnetic field, but further develops hints of an incipient C=2/3 fractional Chern insulator in a modest field. Our results establish moiré R5G as a fertile platform for studying the competition and potential intertwining of integer and fractional Chern insulators. Published by the American Physical Society 2025