Layer-engineered quantum anomalous Hall effect in twisted rhombohedral graphene family

Abstract: The quantum anomalous Hall (QAH) insulator is uniquely characterized by the topological Chern number C. Controlling the Chern number is a key step toward functional topological electronics and enables access to exotic quantum phases beyond the traditional quantum Hall physics. Here, we report a series of QAH insulators in twisted rhombohedral graphene family, in which the Chern number can be tuned through layer configuration, in-situ electrostatic doping, and displacement field. Specifically, in twisted monolayer-rhombohedral N-layer graphene, denoted as (1+N) L, we observe QAH states with C=N at moire filling v=1, where N=3,4,5 represents the layer number of rhombohedral graphene. These results are experimentally confirmed by quantized Hall resistance and the Streda formula. In twisted monolayer-trilayer graphene, we also observe states with |C|=3 at v=3, whose sign can be switched by either electrostatic doping or displacement field. Furthermore, in twisted Bernal bilayer-rhombohedral tetralayer graphene denoted as (2+4) L, we demonstrate a displacement-field-driven topological phase transition between two distinct QAH states with C=3 and C=4 at v=1. Our work establishes twisted rhombohedral graphene as a highly versatile, layer-engineered platform for designing and dynamically controlling high-Chern-number topological matters.