Origin of the Flat Band in Heavily Cs-Doped Graphene

A flat energy dispersion of electrons at the Fermi level of a material leads to instabilities in the electronic system and can drive phase transitions. Here we show that the flat band in graphene can be achieved by sandwiching a graphene monolayer by two cesium (Cs) layers. We investigate the flat b...

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Bibliographic Details
Published in:ACS nano 2020-01, Vol.14 (1), p.1055-1069
Main Authors: Ehlen, Niels, Hell, Martin, Marini, Giovanni, Hasdeo, Eddwi Hesky, Saito, Riichiro, Falke, Yannic, Goerbig, Mark Oliver, Di Santo, Giovanni, Petaccia, Luca, Profeta, Gianni, Grüneis, Alexander
Format: Article
Language:English
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Physics
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Summary:A flat energy dispersion of electrons at the Fermi level of a material leads to instabilities in the electronic system and can drive phase transitions. Here we show that the flat band in graphene can be achieved by sandwiching a graphene monolayer by two cesium (Cs) layers. We investigate the flat band by a combination of angle-resolved photoemission spectroscopy experiment and the calculations. Our work highlights that charge transfer, zone folding of graphene bands, and the covalent bonding between C and Cs atoms are the origin of the flat energy band formation. Analysis of the Stoner criterion for the flat band suggests the presence of a ferromagnetic instability. The presented approach is an alternative route for obtaining flat band materials to twisting bilayer graphene which yields thermodynamically stable flat band materials in large areas.
ISSN:1936-0851
1936-086X
DOI:10.1021/acsnano.9b08622