Intrinsic quantized anomalous Hall effect in a moir\'e heterostructure

Abstract

We report the observation of a quantum anomalous Hall effect in twisted bilayer graphene showing Hall resistance quantized to within .1\% of the von Klitzing constant \(h/e^2\) at zero magnetic field.The effect is driven by intrinsic strong correlations, which polarize the electron system into a single spin and valley resolved moir\'e miniband with Chern number \(C=1\). In contrast to extrinsic, magnetically doped systems, the measured transport energy gap \(\Delta/k_B\approx 27\)~K is larger than the Curie temperature for magnetic ordering \(T_C\approx 9\)~K, and Hall quantization persists to temperatures of several Kelvin. Remarkably, we find that electrical currents as small as 1~nA can be used to controllably switch the magnetic order between states of opposite polarization, forming an electrically rewritable magnetic memory.