▎ 摘　　要

Recent experiments on twisted bilayer graphene show an anomalous quantum Hall (AQH) effect at filling of three electrons per moire unit cell. The AQH effect arises in an insulating state with both valley and ferromagnetic order. We argue that weak doping of such a system leads to the formation of a novel topological spin texture, a "double-tetarton lattice." The building block of this lattice, the "double-tetarton," is a spin configuration which covers 1/4 of the unit sphere twice. In contrast to skyrmion lattices, the net magnetization of this magnetic texture vanishes. Only at large magnetic fields are more conventional skyrmion lattices recovered. But even for large fields the addition of a single charge to the ferromagnetic AQH state flips hundreds of spins. Our analysis is based on the investigation of an effective nonlinear sigma model which includes the effects of long-ranged Coulomb interactions.