Conformational tuning of magnetic interactions in coupled nanographenes

• Published in: arXiv.org 2024-07
• Main Authors: Gonçalo Catarina, Turco, Elia, Krane, Nils, Bommert, Max, Ortega-Guerrero, Andres, Gröning, Oliver, Ruffieux, Pascal, Fasel, Roman, Pignedoli, Carlo A
• Format: Article
• Language: English
• Subjects: Antiferromagnetism; Couplings; Density functional theory; Dihedral angle; Dimers; Electron spin; Electron tunneling; First principles; Functional groups; Hamiltonian functions; Scanning tunneling microscopy; Tuning
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2407.11506

Phenalenyl (C\(_{13}\)H\(_9\)) is an open-shell spin-\(1/2\) nanographene. Using scanning tunneling microscopy (STM) inelastic electron tunneling spectroscopy (IETS), covalently-bonded phenalenyl dimers have been shown to feature conductance steps associated with singlet-triplet excitations of a spin-\(1/2\) dimer with antiferromagnetic exchange. Here, we address the possibility of tuning the magnitude of the exchange interactions by varying the dihedral angle between the two molecules within a dimer. Theoretical methods, ranging from density functional theory calculations to many-body model Hamiltonians solved within different levels of approximation, are used to explain STM-IETS measurements of twisted phenalenyl dimers on a h-BN/Rh(111) surface. By means of first-principles calculations, we also propose strategies to induce sizable twist angles in surface-adsorbed phenalenyl dimers via functional groups, including a photoswitchable scheme. This work paves the way toward tuning magnetic couplings in carbon-based spin chains and two-dimensional lattices.