Moiré superlattices have become a fertile playground for topological Chern insulators, where the displacement field can tune the quantum geometry and Chern number of the topological band. However, in experiments, displacement field engineering of spontaneous symmetry-breaking Chern bands has not been demonstrated. Here in a rhombohedral trilayer graphene moiré superlattice, we use a thermodynamic probe and transport measurement to monitor the Chern number evolution as a function of the displacement field. At a quarter filling of the moiré band, a novel Chern number of three is unveiled to compete with the well-established number of two upon turning on the electric field and survives when the displacement field is sufficiently strong. The transition can be reconciled by a nematic instability on the Fermi surface due to the pseudomagnetic vector field potentials associated with moiré strain patterns. Our work opens more opportunities to active control of Chern numbers in van der Waals moiré systems.

中文翻译：

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设计菱面体三层石墨烯莫尔超晶格中的能带拓扑


莫尔超晶格已成为拓扑陈绝缘体的沃土，其中位移场可以调节拓扑带的量子几何和陈数。然而，在实验中，自发对称破缺陈带的位移场工程尚未得到证实。在菱面体三层石墨烯云纹超晶格中，我们使用热力学探针和输运测量来监测陈数随位移场的变化。当莫尔带充满四分之一时，一种新颖的陈数三被揭开，在打开电场时与成熟的二数竞争，并且当位移场足够强时仍然存在。由于与莫尔应变图案相关的赝磁矢量场势，可以通过费米表面上的向列不稳定性来协调该转变。我们的工作为主动控制范德华莫尔系统中的陈数提供了更多机会。