Jeong Yungi, Park Hangyeol, Kim Taeho, Watanabe Kenji, Taniguchi Takashi, Jung Jeil, Jang Joonho
Center for Correlated Electron Systems, Institute for Basic Science, Seoul, 08826, Korea.
Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea.
Nat Commun. 2024 Jul 28;15(1):6351. doi: 10.1038/s41467-024-50475-x.
In Bernal-stacked bilayer graphene (BBG), the Landau levels give rise to an intimate connection between valley and layer degrees of freedom. Adding a moiré superlattice potential enriches the BBG physics with the formation of topological minibands - potentially leading to tunable exotic quantum transport. Here, we present magnetotransport measurements of a high-quality bilayer graphene-hexagonal boron nitride (hBN) heterostructure. The zero-degree alignment generates a strong moiré superlattice potential for the electrons in BBG and the resulting Landau fan diagram of longitudinal and Hall resistance displays a Hofstadter butterfly pattern with a high level of detail. We demonstrate that the intricate relationship between valley and layer degrees of freedom controls the topology of moiré-induced bands, significantly influencing the energetics of interacting quantum phases in the BBG superlattice. We further observe signatures of field-induced correlated insulators, helical edge states and clear quantizations of interaction-driven topological quantum phases, such as symmetry broken Chern insulators.
在伯纳尔堆叠双层石墨烯（BBG）中，朗道能级在谷自由度和层自由度之间建立了紧密联系。添加莫尔超晶格势会通过形成拓扑微带来丰富BBG的物理特性，这可能会导致可调谐的奇异量子输运。在此，我们展示了高质量双层石墨烯 - 六方氮化硼（hBN）异质结构的磁输运测量结果。零度排列为BBG中的电子产生了强大的莫尔超晶格势，由此产生的纵向和霍尔电阻的朗道扇形图显示出具有高度细节的霍夫施塔特蝴蝶图案。我们证明，谷自由度和层自由度之间的复杂关系控制着莫尔诱导能带的拓扑结构，显著影响了BBG超晶格中相互作用量子相的能量学。我们进一步观察到场诱导关联绝缘体、螺旋边缘态的特征，以及相互作用驱动的拓扑量子相（如对称性破缺的陈绝缘体）的清晰量子化。
