Direct evidence for flat bands in twisted bilayer graphene from nano-ARPES
Abstract
Transport experiments in twisted bilayer graphene revealed multiple superconducting domes separated by correlated insulating states. These properties are generally associated with strongly correlated states in a flat mini-band of the hexagonal moir\'e superlattice as it was predicted by band structure calculations. Evidence for such a flat band comes from local tunneling spectroscopy and electronic compressibility measurements, reporting two or more sharp peaks in the density of states that may be associated with closely spaced van Hove singularities. Direct momentum resolved measurements proved difficult though. 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 homogeneous twist angle that support a flat band with spectral weight that is highly localized in momentum space. The flat band is separated from the dispersive Dirac bands which show multiple moir\'e hybridization gaps. These data establish the salient features of the twisted bilayer graphene band structure.
Keywords
Cite
@article{arxiv.2002.02289,
title = {Direct evidence for flat bands in twisted bilayer graphene from nano-ARPES},
author = {Simone Lisi and Xiaobo Lu and Tjerk Benschop and Tobias A. de Jong and Petr Stepanov and Jose R. Duran and Florian Margot and Irène Cucchi and Edoardo Cappelli and Andrew Hunter and Anna Tamai and Viktor Kandyba and Alessio Giampietri and Alexei Barinov and Johannes Jobst and Vincent Stalman and Maarten Leeuwenhoek and Kenji Watanabe and Takashi Taniguchi and Louk Rademaker and Sense Jan van der Molen and Milan Allan and Dmitri K. Efetov and Felix Baumberger},
journal= {arXiv preprint arXiv:2002.02289},
year = {2020}
}
Comments
Submitted to Nature Materials. Nat. Phys. (2020)