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Electronic correlations in twisted bilayer graphene near the magic angle

2019; Nature Portfolio; Volume: 15; Issue: 11 Linguagem: Inglês

10.1038/s41567-019-0606-5

1745-2481

Youngjoon Choi, Jeannette Kemmer, Yang Peng, Alex Thomson, Harpreet Singh Arora, Robert Polski, Yiran Zhang, Hechen Ren, Jason Alicea, Gil Refael, Felix von Oppen, Kenji Watanabe, Takashi Taniguchi, Stevan Nadj-Perge,

Topological Materials and Phenomena

Twisted bilayer graphene with a twist angle of around 1.1{\deg} features a pair of isolated flat electronic bands and forms a strongly correlated electronic platform. Here, we use scanning tunneling microscopy to probe local properties of highly tunable twisted bilayer graphene devices and show that the flat bands strongly deform when aligned with the Fermi level. At half filling of the bands, we observe the development of gaps originating from correlated insulating states. Near charge neutrality, we find a previously unidentified correlated regime featuring a substantially enhanced flat band splitting that we describe within a microscopic model predicting a strong tendency towards nematic ordering. Our results provide insights into symmetry breaking correlation effects and highlight the importance of electronic interactions for all filling factors in twisted bilayer graphene.