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Twisted bilayer graphene (tBLG) provides a fascinating platform for engineering flat bands and inducing correlated phenomena. By increasing the number of stacked graphene layers, twisted multilayer graphene can exhibit different symmetries with rich tunabilities. For example, for twisted monolayer-bilayer graphene (tMBG) which breaks the C2z symmetry, transport measurements reveal an asymmetric phase diagram under an out-of-plane electric field, exhibiting correlated insulating state and ferromagnetic state respectively when reversing the field direction. Revealing the electronic structure evolution with electric field is critical for understanding such asymmetric field tunable properties. Here we report the experimental observation of dichotomic electronic structure response of tMBG to bias voltage by nanospot angle-resolved photoemission spectroscopy (NanoARPES) with operando gating. Spectral weight contributions from monolayer and bilayer graphene are selectively enhanced by switching the bias voltage, and dispersive bands similar to tBLG are observed under positive bias voltage (electric field pointing from monolayer to bilayer graphene), while in contrast, more pronounced flat bands resembling those in twisted double bilayer graphene (tDBG) are observed under negative bias voltage. Combing experimental results with theo- retical calculations, the origin of such field tunable electronic structure is attributed to the field induced population of carriers into different stacked graphene layers with enhanced electron-hole asymmetry dictated by the asymmetric stacking. Our work provides electronic structure insights for understanding the rich field-tunable physics of tMBG.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: Twisted bilayer graphene, flat bands, field-tunable properties

刊行年月日: 2024-05-03

出版者: Springer Science and Business Media LLC

掲載誌:

• Nature Communications (ISSN: 20411723) vol. 15 issue. 1 3737

研究助成金:

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1038/s41467-024-48166-8

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更新時刻: 2025-02-27 12:30:45 +0900

MDRでの公開時刻: 2025-02-27 12:30:45 +0900