▎ 摘　　要

Twisted graphene bilayers provide a versatile platform to engineer metamaterials with novel emergent properties by exploiting the resulting geometric moire superlattice. Such superlattices are known to host bulk valley currents at tiny angles (alpha approximate to 0.3 degrees) and flat bands at magic angles (alpha approximate to 1 degrees). We show that tuning the twist angle to alpha* approximate to 0.8 degrees generates flat bands away from charge neutrality with a triangular superlattice periodicity. When doped with +/- 6 electrons per moire cell, these bands are half-filled and electronic interactions produce a symmetry-broken ground state (Stoner instability) with spin-polarized regions that order ferromagnetically. Application of an interlayer electric field breaks inversion symmetry and introduces valley-dependent dispersion that quenches the magnetic order. With these results, we propose a solid-state platform that realizes electrically tunable strong correlations.