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Controlling the electronic structure of two-dimensional materials using the combination of twist angle and electrostatic doping is an effective means to induce emergent phenomena. In bilayer graphene with an interlayer twist angle near the magic angle, the electronic dispersion is strongly modified by a manifold of hybridizing moiré Dirac cones leading to flat band segments with strong electronic correlations. Numerous technical challenges arising from spatial inhomogeneity of interlayer interactions, twist angle and device functionality have so far limited momentum-resolved electronic structure measurements of these systems to static conditions. Here, we present a detailed characterization of the electronic structure exhibiting miniband dispersions for twisted bilayer graphene, near the magic angle, integrated in a functional device architecture using micro-focused angle-resolved photoemission spectroscopy. The optimum conditions for visualizing the miniband dispersion are determined by exploiting the spatial resolution and photon energy tunability of the light source and applied to extract a hybridization gap size of (0.14 ± 0.03) eV and flat band segments extending across a moiré mini Brillouin zone. In situ electrostatic gating of the sample enables significant electron-doping, causing the conduction band states to shift below the Fermi energy. Our work emphasizes key challenges in probing the electronic structure of magic angle bilayer graphene devices and outlines conditions for exploring the doping-dependent evolution of the dispersion that underpins the ability to control many-body interactions in the material.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Twisted bilayer graphene, electrostatic doping, miniband dispersions

Date published: 2023-10-01

Publisher: IOP Publishing

Journal:

• 2D Materials (ISSN: 20531583) vol. 10 issue. 4 045027

Funding:

• JSPS
• Villum Investigator Program 25931
• World Premier International Research Center Initiative (WPI), MEXT, Japan
• KAKENHI 20H00354
• Danish Council for Independent Research DFF-9064-00057B
• Natur og Univers, Det Frie Forskningsråd DFF-6108-00409
• Villum Fonden
• Novo Nordisk NNF22OC0079960

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

MDR DOI:

First published URL: https://doi.org/10.1088/2053-1583/acf775

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Updated at: 2025-02-14 12:30:34 +0900

Published on MDR: 2025-02-14 12:30:34 +0900