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Superlattices from twisted graphene mono- and bilayer systems give rise to on-demand many-body states such as Mott insulators and unconventional superconductors. These phenomena are ascribed to a combination of flat bands and strong Coulomb interactions. However, a comprehensive understanding is lacking because the low-energy band structure strongly changes when an electric field is applied to vary the
electron filling. Here, we gain direct access to the filling- dependent low-energy bands of twisted bilayer graphene (TBG)
and twisted double bilayer graphene (TDBG) by applying
microfocused angle-resolved photoemission spectroscopy to in
situ gated devices. Our findings for the two systems are in stark
contrast: the doping-dependent dispersion for TBG can be
described in a simple model, combining a filling-dependent rigid band shift with a many-body-related bandwidth change. In TDBG, on the other hand, we find a complex behavior of the low-energy bands, combining nonmonotonous bandwidth changes and tunable gap openings, which depend on the gate-induced displacement field. Our work establishes the extent of electric field tunability of the low-energy electronic states in twisted graphene superlattices and can serve to underpin the theoretical understanding of the resulting phenomena.

Rights:

• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

Keyword: Twisted graphene, low-energy bands, photoemission spectroscopy

Date published: 2025-01-21

Publisher: American Chemical Society (ACS)

Journal:

• ACS Nano (ISSN: 19360851) vol. 19 issue. 2 p. 2379-2387

Funding:

• Det Frie Forskningsr??d DFF-9064-00057B
• Novo Nordisk Fonden NNF22OC0079960
• HORIZON EUROPE Marie Sklodowska-Curie Actions 101059528
• Aarhus Universitets Forskningsfond
• Korea Institute of Science and Technology Information KSC-2022-CRE-0514
• Villum Fonden 25931
• Ministry of Education, Culture, Sports, Science and Technology 21H05233
• Ministry of Education, Culture, Sports, Science and Technology 23H02052
• Ministry of Land, Infrastructure and Transport
• Ministry of Education, Culture, Sports, Science and Technology
• National Research Foundation of Korea NRF2020R1A5A1016518
• Det Frie Forskningsr??d DFF-1026-00089B
• Det Frie Forskningsr??d DFF-6108-00409

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1021/acsnano.4c12905

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Updated at: 2025-02-05 12:30:18 +0900

Published on MDR: 2025-02-05 12:30:18 +0900