The recent observation of the fractional quantum anomalous Hall effect in moiré fractional Chern insulators provides an opportunity to investigate zero magnetic field anyons. One approach for potentially realizing non-abelian anyons is to engineer higher flat Chern bands that mimic higher Landau levels. We investigate the interaction, topology and ferromagnetism of the second moiré miniband in twisted MoTe₂ bilayers. At half-filling of the second miniband, we observed spontaneous ferromagnetism and an incipient Chern insulator state. The Chern numbers of the top two moiré flat bands exhibited opposite signs for twist angles above 3.1° but had the same sign near 2.6°, consistent with theoretical predictions. In the 2.6° device, increasing the magnetic field induced a topological phase transition due to band-crossing between opposite valleys, resulting in an emergent state with Chern number C = −2. Additionally, an insulating state at half-filling of the second valley-polarized band indicates that a charge-ordered state is favoured over the fractional Chern insulator state. These findings lay a foundation for understanding the higher flat Chern bands, which are crucial for the discovery of non-abelian fractional Chern insulators.

最近在莫尔色分场陈绝缘体中观察到的分数量子反常霍尔效应为研究零磁场任意子提供了机会。可能实现非阿贝尔任意子的一种方法是设计更高的平坦陈带，以模拟更高的朗道能级。我们研究了扭曲 MoTe₂ 双层中第二个莫尔迷你带的相互作用、拓扑结构和铁磁性。在第二个迷你带的一半填充时，我们观察到自发的铁磁性和初期的 Chern 绝缘体状态。顶部两个莫尔条纹平带的陈数在 3.1° 以上的扭曲角上表现出相反的符号，但在 2.6° 附近具有相同的符号，这与理论预测一致。在 2.6° 器件中，由于相对谷之间的带交叉，增加磁场会诱导拓扑相变，从而导致陈数 C = −2 的紧急状态。此外，第二个谷极化带半填充时的绝缘态表明电荷有序状态优于分数陈绝缘体状态。这些发现为理解高等平坦的陈氏带奠定了基础，这对于发现非阿贝尔分数陈绝缘子至关重要。