Revealing flat bands and hybridization gaps in a twisted bilayer graphene device with microARPES

Zhihao Jiang*, Kimberly Hsieh, Alfred J.H. Jones, Paulina Majchrzak, Chakradhar Sahoo, Kenji Watanabe, Takashi Taniguchi, Jill A. Miwa, Yong P. Chen, Søren Ulstrup*

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

Abstract

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.

Original languageEnglish
Article number045027
Journal2D materials
Volume10
Issue4
Number of pages10
ISSN2053-1583
DOIs
Publication statusPublished - Oct 2023

Keywords

  • electronic structure
  • in situ gating
  • magic angle bilayer graphene
  • microARPES
  • moiré superlattice

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