Decoding Molecular Orbitals

Electron distribution in a sigma-orbital of the graphene-like molecule bisanthene. - Image: Uni Graz / Dominik Brandstetter

A recent study published in Physical Review B by researchers from the “Orbital Cinema” team from the Physics Institute at the University of Grazand the Forschungszentrum Jülich presents a remarkable breakthrough in molecular electronics. The team, led by Peter Puschnig and Stefan Tautz, successfully mapped the electronic structure of bisanthene—a molecule that can be considered a nano-graphene flake—on a metal surface. Using a technique called photoemission orbital tomography, developed at the Institute of Physics, they deciphered the electron distribution in an unprecedented 38 (!) molecular orbitals.

These insights not only push the boundaries of experimental physics but also serve as a crucial benchmark for advancing theoretical calculation methods. The comparison between theory and experiment led to a surprising discovery that challenges long-standing assumptions regarding the underlying density functional theory.

The study’s results suggest that the common interpretation of so-called Kohn-Sham orbitals as an approximation for electron states may be more reliable than previously assumed. Furthermore, these new insights into the electronic properties of this nano-graphene molecule pave the way for future applications in the field of organic solar cells. Or, in the words of one of the peer reviewers: "I think the scientific community will be extremely pleased to see this manuscript appear in Physical Review B!"

Publication:

Tomographic identification of all molecular orbitals in a wide binding-energy range,
Haags, A.; Brandstetter, D.; Yang, X.; Egger, L.; Kirschner, H.; Gottwald, A.; Richter, M.; Koller, G.; Bocquet, F. C.; Wagner, C.; Ramsey, M. G.; Soubatch, S.; Puschnig, P. & Tautz, F. S, Phys. Rev. B 111, 165402 (2025)
https://doi.org/10.1103/PhysRevB.111.165402

Peter Puschnig

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