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

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


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 languageEnglish
Pages (from-to)1055-1069
Number of pages15
JournalACS Nano
Issue number1
Publication statusPublished - 2020 Jan 28


  • 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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