Hofstadter subband ferromagnetism and symmetry-broken Chern insulators in twisted bilayer graphene

When the twist angle between two layers of graphene is approximately 1.1°, interlayer tunnelling and rotational misalignment conspire to create a pair of flat bands1 that are known to host various insulating, superconducting and magnetic states when they are partially filled2–7. Most work has focused on the zero-magnetic-field phase diagram, but here we show that twisted bilayer graphene in a finite magnetic field hosts a cascade of...