Fractional Chern insulators in magic-angle twisted bilayer graphene

Fractional Chern insulators (FCIs) are lattice analogues of fractional quantum Hall states that may provide a new avenue toward fractionalized and non-abelian excitations even at zero magnetic field. Early theoretical studies have predicted their existence in systems with energetically flat Chern bands and highlighted the critical role of a particular quantum band geometry. Magic angle twisted bilayer graphene (MATBG) supports flat Chern bands at zero magnetic field, and therefore offers a promising route toward stabilizing zero-field FCIs. Here we describe our recent observation of FCI states at low magnetic fields in MATBG enabled by high-resolution local compressibility measurements. Our findings highlight the interplay between symmetry, topology and interactions that leads to a competition between ordered electronic solid phases and fractionalized electronic liquid phases. Our findings strongly suggest that FCIs may be realized at zero magnetic field and pave the way for the exploration and manipulation of anyonic excitations in moiré systems.