Conformational tuning of magnetic interactions in coupled nanographenes

Abstract

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.

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Cited by in corpus (4)

• Artificially built Kondo chains with organic radicals on metallic surfaces: new model system of heavy fermion quantum criticality
• The multiconfigurational ground state of a diradicaloid characterized at the atomic scale
• Quantum Spin-1/2 Rings Built from [2]Triangulene Molecular Units
• Identification and optimization of accurate spin models for Fermi-Hubbard ladders using matrix product states