Tomographic identification of all molecular orbitals in a wide binding-energy range

Physical review. B./Physical review. B, vol. 111

Abstract

In the past decade, photoemission orbital tomography (POT) has evolved into a powerful tool to investigate the electronic structure of organic molecules adsorbed on surfaces. Here we show that POT allows for the comprehensive experimental identification of all molecular orbitals in a substantial binding energy range of more than 10 eV. Making use of the angular distribution of photoelectrons as a function of binding-energy, we exemplify this by extracting an orbital-resolved projected density of states for 15 π and 23 σ orbitals from the experimental data of the prototypical organic molecule bisanthene ( C 28 H 14 ) on a Cu(110) surface. These experimental results for an essentially complete set of orbitals within the given binding-energy range serve as stringent benchmarks for electronic structure methods, which we illustrate by performing density functional calculations employing four frequently used exchange-correlation functionals. By computing the respective molecular-orbital-projected densities of states, a one-to-one comparison with experimental data for an unprecedented number of 38 orbital energies became possible. The quantitative analysis of our data reveals that the range-separated hybrid functional HSE performs best for the investigated organic/metal interface. At a more fundamental level, the remarkable agreement between the experimental and the Kohn-Sham orbital energies over a binding-energy range larger than 10 eV suggests that—perhaps unexpectedly—Kohn-Sham orbitals approximate Dyson orbitals, which would rigorously account for the electron extraction process in photoemission spectroscopy but are notoriously difficult to compute, in a much better way than previously thought.

Authors 14

1. Anja Haags Aachen

   RWTH Aachen University · Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Forschungszentrum Jülich

   Jülich Aachen Research Alliance (JARA)

   RWTH Aachen University

2. Dominik Brandstetter

   University of Graz

   Affiliation as printed

   University of Graz

3. Xiaosheng Yang Aachen

   RWTH Aachen University · Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Forschungszentrum Jülich

   Jülich Aachen Research Alliance (JARA)

   RWTH Aachen University

4. Larissa Egger

   University of Graz

   Affiliation as printed

   University of Graz

5. Hans Kirschner

   Physikalisch-Technische Bundesanstalt

   Affiliation as printed

   Physikalisch-Technische Bundesanstalt (PTB)

6. Alexander Gottwald

   Physikalisch-Technische Bundesanstalt

   Affiliation as printed

   Physikalisch-Technische Bundesanstalt (PTB)

7. M. Richter

   Physikalisch-Technische Bundesanstalt

   Affiliation as printed

   Physikalisch-Technische Bundesanstalt (PTB)

8. Georg Koller

   University of Graz

   Affiliation as printed

   University of Graz

9. François C. Bocquet

   Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Forschungszentrum Jülich

   Jülich Aachen Research Alliance (JARA)

10. Christian Wagner

    Forschungszentrum Jülich · Jülich Aachen Research Alliance

    Affiliation as printed

    Forschungszentrum Jülich

    Jülich Aachen Research Alliance (JARA)

11. Michael G. Ramsey

    University of Graz

    Affiliation as printed

    University of Graz

12. Serguei Soubatch

    Forschungszentrum Jülich · Jülich Aachen Research Alliance

    Affiliation as printed

    Forschungszentrum Jülich

    Jülich Aachen Research Alliance (JARA)

13. Peter Puschnig corresponding

    University of Graz

    Affiliation as printed

    University of Graz

14. Frank Stefan Tautz Aachen

    RWTH Aachen University · Forschungszentrum Jülich · Jülich Aachen Research Alliance

    Affiliation as printed

    Forschungszentrum Jülich

    Jülich Aachen Research Alliance (JARA)

    RWTH Aachen University