Interplay of valley, layer and band topology towards interacting quantum phases in moiré bilayer graphene

Yungi Jeong; Hangyeol Park; Taeho Kim; Kenji Watanabe; Takashi Taniguchi; Jeil Jung; Joonho Jang

doi:10.1038/s41467-024-50475-x

論文 Interplay of valley, layer and band topology towards interacting quantum phases in moiré bilayer graphene

Yungi Jeong ; Hangyeol Park ; Taeho Kim ; Kenji Watanabe ; Takashi Taniguchi ; Jeil Jung ; Joonho Jang

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Yungi Jeong, Hangyeol Park, Taeho Kim, Kenji Watanabe, Takashi Taniguchi, Jeil Jung, Joonho Jang. Interplay of valley, layer and band topology towards interacting quantum phases in moiré bilayer graphene. Nature Communications. 2024, 15 (1), 6351. https://doi.org/10.1038/s41467-024-50475-x

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(abstract)

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 influen- cing 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.

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