Electronic Characterization of a Charge-Transfer Complex Monolayer on Graphene
journal contributionposted on 2021-05-24, 13:41 authored by Avijit Kumar, Kaustuv Banerjee, Mikko M. Ervasti, Shawulienu Kezilebieke, Marc Dvorak, Patrick Rinke, Ari Harju, Peter Liljeroth
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.
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electron donor moleculesground statesTCNQsurfaceoxygen-intercalated epitaxial grapheneGraphene Organic charge-transfer co...electron acceptorTTFmonolayer CTCElectronic CharacterizationformationV spectroscopyLT-STMCharge-Transfer Complex Monolayerscanning tunneling microscopyresults pointHigh-resolution spectroscopyground statecharge density waves