Electronic Characterization of a Charge-Transfer Complex Monolayer on Graphene

Avijit Kumar*, Kaustuv Banerjee, Mikko M. Ervasti, Shawulienu Kezilebieke, Marc Dvorak, Patrick Rinke, Ari Harju, Peter Liljeroth

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

Organic charge-transfer complexes (CTCs) formed by strong electron acceptor and strong electron donor molecules are known to exhibit exotic effects such as superconductivity and charge density waves. We present a low-temperature scanning tunneling microscopy and spectroscopy (LT-STM/STS) study of a two-dimensional (2D) monolayer CTC of tetrathiafulvalene (TTF) and fluorinated tetracyanoquinodimethane (F4TCNQ), self-assembled on the surface of oxygen-intercalated epitaxial graphene on Ir(111) (G/O/Ir(111)). We confirm the formation of the charge-transfer complex by dI/dV spectroscopy and direct imaging of the singly occupied molecular orbitals. High-resolution spectroscopy reveals a gap at zero bias, suggesting the formation of a correlated ground state at low temperatures. These results point to the possibility to realize and study correlated ground states in charge-transfer complex monolayers on weakly interacting surfaces.

Original languageEnglish
Pages (from-to)9945-9954
Number of pages10
JournalACS Nano
Volume15
Issue number6
Early online date2021
DOIs
Publication statusPublished - 22 Jun 2021
MoE publication typeA1 Journal article-refereed

Keywords

  • charge density wave (CDW)
  • charge-transfer complex
  • epitaxial graphene
  • FTCNQ
  • scanning tunneling microscopy (STM)
  • TTF

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