Observation of a flat band and bandgap in millimeter-scale twisted bilayer graphene

Magic-angle twisted bilayer graphene is interesting for its correlated superconducting and insulating states, but samples are typically micrometer-scale. Here, 3 x 5 mm(2) twisted bilayer graphene samples are fabricated, exhibiting a flat band and large bandgap revealed by angle-resolved photoemission spectroscopy. Magic-angle twisted bilayer graphene, consisting of two graphene layers stacked at a special angle, exhibits superconductivity due to the maximized density of states at the energy of the flat band. Generally, experiments on twisted bilayer graphene have been performed using micrometer-scale samples. Here we report the fabrication of twisted bilayer graphene with an area exceeding 3 x 5 mm(2) by transferring epitaxial graphene onto another epitaxial graphene, and observation of a flat band and large bandgap using angle-resolved photoemission spectroscopy. Our results suggest that the substrate potential induces both the asymmetrical doping in large angle twisted bilayer graphene and the electron doped nature of the flat band in magic-angle twisted bilayer graphene.

Automated summary

Researchers fabricated twisted bilayer graphene samples with an area exceeding 3 x 5 mm(2) and observed a flat band and large bandgap using angle-resolved photoemission spectroscopy, indicating the presence of superconductivity.