Origin of the Flat Band in Heavily Cs-Doped Graphene

Niels Ehlen; Martin Hell; Giovanni Marini; Eddwi Hesky Hasdeo; Riichiro Saito; Yannic Falke; Mark Oliver Goerbig; Giovanni Di Santo; Luca Petaccia; Gianni Profeta; Alexander Grüneis

doi:10.1021/acsnano.9b08622

Origin of the Flat Band in Heavily Cs-Doped Graphene

Niels Ehlen, Martin Hell, Giovanni Marini, Eddwi Hesky Hasdeo, Riichiro Saito, Yannic Falke, Mark Oliver Goerbig, Giovanni Di Santo, Luca Petaccia, Gianni Profeta, Alexander Grüneis

SCI - Physics

Research output: Contribution to journal › Article › peer-review

21 Citations (Scopus)

Abstract

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.

Original language	English
Pages (from-to)	1055-1069
Number of pages	15
Journal	ACS Nano
Volume	14
Issue number	1
DOIs	https://doi.org/10.1021/acsnano.9b08622
Publication status	Published - 2020 Jan 28

Keywords

Stoner criterion
alkali-metal intercalation compound
angle resolved photoemission spectroscopy
flat band
graphene

ASJC Scopus subject areas

Materials Science(all)
Engineering(all)
Physics and Astronomy(all)

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10.1021/acsnano.9b08622

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title = "Origin of the Flat Band in Heavily Cs-Doped Graphene",

abstract = "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.",

keywords = "Stoner criterion, alkali-metal intercalation compound, angle resolved photoemission spectroscopy, flat band, graphene",

author = "Niels Ehlen and Martin Hell and Giovanni Marini and Hasdeo, {Eddwi Hesky} and Riichiro Saito and Yannic Falke and Goerbig, {Mark Oliver} and {Di Santo}, Giovanni and Luca Petaccia and Gianni Profeta and Alexander Gr{\"u}neis",

note = "Funding Information: N.E., M.H., and A.G. acknowledge the ERC-grant no. 648589 {\textquoteleft}SUPER-2D{\textquoteright} and funding from Quantum Matter and Materials as well as CRC1238 project A1. The stay at the Elettra synchrotron for ARPES experiments was supported by Horizon 2020 EC program under grant agreement no. 730872 (CALIPSOplus). H.H. acknowledges funding from DAAD for a stay in Germany. R.S. acknowledges JSPS KAKENHI (No. JP18H01810). Figures 2b–d, 3e, and 4 were created using Matplotlib v3.1. (74) Figure 3a–d was generated using the pybinding package for python3. (75) The Mayavi software was used to generate Figure 3f. (76) Publisher Copyright: Copyright {\textcopyright} 2019 American Chemical Society.",

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doi = "10.1021/acsnano.9b08622",

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AU - Ehlen, Niels

AU - Hell, Martin

AU - Marini, Giovanni

AU - Hasdeo, Eddwi Hesky

AU - Saito, Riichiro

AU - Falke, Yannic

AU - Goerbig, Mark Oliver

AU - Di Santo, Giovanni

AU - Petaccia, Luca

AU - Profeta, Gianni

AU - Grüneis, Alexander

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PY - 2020/1/28

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N2 - 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.

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Origin of the Flat Band in Heavily Cs-Doped Graphene

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Keywords

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