▎ 摘　　要

The dominance of Coulomb interactions over the kinetic energy of electrons in flat moire bands of magic-angle twisted bilayer graphene (TBG) gives rise to a variety of correlated phases, including correlated insulators(1-3), superconductivity(2,4,5), orbital ferromagnetism(2,6), Chern insulators(7-10) and nematicity(11). Most of these phases occur when the carrier density is at or near an integer number of carriers per moire unit cell. However, the demonstration of ordered states at fractional moire band fillings at zero applied magnetic field is more challenging. Here we report the observation of states near half-integer band fillings 0.5 and +/- 3.5 at near-zero magnetic field in TBG proximitized by tungsten diselenide. Furthermore, at a band filling near -0.5, a symmetry-broken Chern insulator emerges at high magnetic field that is compatible with the band structure calculations within a translational symmetry-broken supercell with twice the area of the original TBG moire cell. Our results are consistent with a spin or charge density wave ground state in TBG in the zero-magnetic-field limit.