Intrinsic quantized anomalous Hall effect in a moiré heterostructure, part II: Temperature dependence and current switching

This is the second of three talks describing the observation and characterization of a ferromagnetic moiré heterostructure based on twisted bilayer graphene aligned to hexagonal boron nitride. I will compare the qualitative and quantitative features of this observed quantum anomalous Hall state to traditional systems engineered from thin film (Bi,Sb)2Te3 topological insulators. In particular, we find that the measured electronic energy gap of ~30K is several times higher than the Curie temperature, consistent with a lack of disorder associated with magnetic dopants. In this system, the quantization arises from spontaneous ferromagnetic polarization into a single spin and valley moiré subband, which is topological despite the lack of spin orbit coupling. I will also discuss the observation of current induced switching, which allows the magnetic state of the heterostructure to be controllably reversed with currents as small as a few nanoamperes.