Theory of fractional quantum anomalous Hall phases in pentalayer rhombohedral graphene moir\'e structures

Remarkable recent experiments on the moir\'e structure formed by pentalayer rhombohedral graphene aligned with a hexagonal Boron-Nitride substrate report the discovery of a zero field fractional quantum hall effect. These ``Fractional Quantum Anomalous Hall'' (FQAH) phases occur for one sign of a perpendicular displacement field, and correspond, experimentally, to full or partial filling of a valley polarized Chern-$1$ band. Here we present microscopic theoretical calculations demonstrating the emergence of a Chern-$1$ band and the FQAH phases in this system. We also study the four and six-layer analogs and identify parameters where a nearly flat isolated Chern-$1$ band emerges which may be suitable to host FQAH physics.