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O: Fachverband Oberflächenphysik
O 51: Focus Session: Molecular Nanostructures on Surfaces: On-Surface Synthesis and Single-Molecule Manipulation II
O 51.4: Vortrag
Mittwoch, 20. März 2024, 16:00–16:15, HE 101
Charge states and electron correlation in graphene nanoribbons on MgO — •Leonard Edens1, Amelia Domínguez Celorrio2, Manuel Vilas-Varela3, Sofia Sanz4, Thomas Frederikssen4, Diego Peña3, Nacho Pascual1, and David Serrate2 — 1CIC nanoGUNE, Spain — 2CSIC-INMA and Universidad de Zaragoza, Spain — 3CiQUS and Universidade de Santiago de Compostela, Spain — 4DIPC, Spain
On-surface synthesis of graphene nanostructures provides tailor-made systems exhibiting quantum properties such as π magnetism. However, the underlying catalyst metal readily hybridizes with molecular orbitals and quenches spin. Here, we report the successful lateral STM manipulation of individual graphene nanoribbons onto epitaxial layers of MgO(001) after synthesis on Ag(001). We observe a rich electronic spectrum of large absolute gaps straddled by remarkably sharp resonances implying drastic lifetime enhancement. LDOS mapping allows exact determination of the large integer negative charge acquired due to the low insulator work function. We find that the integer charge state of the molecule depends on its length, leading to an opening and closing of the correlation gap with charge parity. Studying charge as a function of length shows that the electronic state alternates between open- and closed-shell as determined by the interplay between level evolution with length and electron correlation. We introduce a mean-field Hubbard model in the grand canonical ensemble that reproduces and predicts the charging behaviour and allows us to extract the energy of the graphene-metal interface dipole across the insulator.
Keywords: Nanoribbons; MgO; STM; Open-shell; On-surface synthesis