Extended fractional Chern insulators near half flux in twisted bilayer graphene above the magic angle

Twisted bilayer graphene hosts a plethora of correlated electronic states when twisted to its magic angle of 1.1 degrees. When tuned only two tenths of a degree above the magic angle, its zero-field correlated states vanish. We previously demonstrated excellent agreement between low-field magnetotransport measurements and single-particle continuum model calculations of a twisted bilayer graphene sample at 1.38 degree twist angle. Here we report a set of strongly correlated states in measurements taken on the same sample at high field. Near half of a magnetic flux quantum per moir´e unit cell, we observe numerous regions of well-quantized odd-denominator fractional Chern insulating states. Several regions of quantization persist over unusually extended ranges of density and field. Though we cannot explicitly rule out more mundane explanations, we believe an atypical mechanism is stabilizing the fractional state such as the excess carriers forming a Wigner crystal as in a partial-Hall crystal. Strong magnetic fields can thus induce strongly correlated electronic phases even in twisted bilayer graphene samples well away from the magic angle.