Observation of flat bands in twisted bilayer graphene

Author(s):
Lisi, S.; Lu, X.; Benschop, T.; Jong, T.A. de (0000-0002-5211-8081); Stepanov, P.; Duren, J.R.; Margot, F.; Cucchi, I.; Cappelli, E.; Hunter, A.; Tamai, A.; Kandyba, V.; Giampietri, A.; Barinov, A.; Jobst, J. (0000-0002-2422-1209); Stalman, V.R.; Leeuwenhoek, M.; Watanabe, K.; Taniguchi, T.; Rademaker, L.; Molen, S.J. van der (0000-0003-3181-2055); Allan, M.P. (0000-0002-5437-1945); Efetov, D.K.; Baumberger, F.
Published
2020
Publication type
Article / Letter to editor

Abstract

Transport experiments in twisted bilayer graphene have

revealed multiple superconducting domes separated by cor-

related insulating states 1–5 . These properties are generally

associated with strongly correlated states in a flat mini-band of the hexagonal moiré superlattice as was predicted by band structure calculations 6–8 . Evidence for the existence of a flat band comes from local tunnelling spectroscopy 9–13 and elec- tronic compressibility measurements 14 , which report two or more sharp peaks in the density of states that may be asso- ciated with closely spaced Van Hove singularities. However, direct momentum-resolved measurements have proved to be challenging 15 . Here, we combine different imaging techniques and angle-resolved photoemission with simultaneous real- and momentum-space resolution (nano-ARPES) to directly map the band dispersion in twisted bilayer graphene devices near charge neutrality. Our experiments reveal large areas with a homogeneous twist angle that support a flat band with a spec- tral weight that is highly localized in momentum space. The flat band is separated from the dispersive Dirac bands, which show multiple moiré hybridization gaps. These data establish the salient features of the twisted bilayer graphene band structure.

Low-Energy Electron MicroscopygraphenesuperconductivityAngle-resolved photoemission spectroscopyScanning Tunneling MicroscopeLEEMARPESSTM
Date issued
2020-09-28
Language
English
Is part of
Nature Physics (2020), Vol. 17, p. 189-193
hdl
1887/3185540
doi
10.1038/s41567-020-01041-x
Dataset
https://doi.org/10.26037/yareta:nxtqgcnllzbklcak4qyzi3adv4