Integer and fractional quantum anomalous Hall effects in pentalayer graphene

Through a critical analysis of transport data from the recently discovered fractional quantum anomalous Hall effect (FQAHE) in rhombohedral pentalayer graphene on hBN, the authors identify here significant discrepancies between the FQAHE and the conventional fractional quantum Hall effect in Landau levels. Most notably, the excitation gap remains nearly constant for all observed fractions, starkly contrasting with the ``v''-shaped linear dependence on |ν-1/2| predicted by the composite fermion model. This uncovers an intriguing puzzle regarding the nature of the FQAHE states.