Regensburg 2025 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 45: Poster Spins on Surfaces at the Atomic Scale
O 45.14: Poster
Dienstag, 18. März 2025, 18:00–20:00, P2
Exchange interactions of spin states in coupled triangular nanographenes — •Suyash Singh1, Nils Krane1, Elia Turco1, Roman Fasel1,2, and Pascal Ruffieux1 — 1Empa - Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf (Switzerland) — 2Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland
Zigzag-edged triangular nanographenes (triangulenes) are promising realizations of spin qubits at a molecular level, with a total spin S scaling with the length of their edges. Chemical design and on-surface synthesis methods allow atomically precise engineering of carbon-based π–systems with strong spin-spin interactions, using triangulene units as building blocks. Exploiting the rules governing the exchange interactions, functional groups and spacer molecules, such as phenyl rings, can be used to tune the sign and magnitude of the exchange coupling between the triangulene units. We present the bottom-up fabrication of correlated spin platforms using the two smallest members of the triangulene family, the spin S=1/2 phenalenyl and S=1 [3]triangulene. We analyze the origin of spin-polarized states and spin excitations using a tight-binding and mean-field Hubbard Model for the π–orbital network. With an estimate of the couplings within the spin cluster, we describe it using an effective Heisenberg model. The spin excitations are then investigated experimentally using inelastic electron tunneling spectroscopy. Specifically, we summarize the results on dimers and trimers, where the exchange mechanisms can be investigated systematically by hydrogenation and selective re-activation of single spins.
Keywords: spin qubit; quantum magnetism; carbon-based magnetism; spin excitation; tunneling spectroscopy