Composite fermion theory of fractional Chern insulators in rhombohedral graphene

The experimental observation of the fractional quantum anomalous Hall effect in rhombohedral graphene multilayers has raised questions about the nature of the fractional Chern insulator states and the importance of the moir\'e potential. In this talk I will present a composite fermion description of the system and discuss the effects of the moir\'e potential on the composite fermion spectrum. Under the flux-attachment transformation and mean-field approximation, the composite fermion spectrum forms Landau levels that are further split by the moir\'e potential. At moir\'e filling fractions in the Jain sequence, an integer number of bands are occupied, resulting in an incompressible ground state. Remarkably, because of the chirality of the rhombohedral graphene bands, the composite fermion Landau levels are widely spaced in energy and delocalized across layers, leading to amplified modulation on the composite fermion spectrum when the moir\'e potential acts on the layer away from the doped electrons. Our work qualitatively explains the importance of the moir\'e potential in stabilizing the fractional Chern insulator ground states and provides a theoretical framework for further studies.