Berlin 2024 – scientific programme

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O: Fachverband Oberflächenphysik

O 21: Focus Session: Spins on Surfaces studied by Atomic Scale Spectroscopies III

O 21.9: Talk

Tuesday, March 19, 2024, 12:45–13:00, MA 004

From single electron ratio rules to atoms on surfaces – A relativistic investigation of hyperfine splittings — •Katharina Lorena Franzke, Wolf Gero Schmidt, and Uwe Gerstmann — Paderborn University, Warburger Str. 100, 33098 Paderborn

The hyperfine splitting of a given system is caused by the interaction of the electronic spin with the magnetic moments of the nuclei and leads to comparably small energy shifts in the absorption spectra. These shifts can be split into the isotropic Fermi contact, the anisotropic dipolar and the orbital part. In many systems, especially in semiconductors, the hybridization and deformation of the atomic orbitals by the crystal field leads to the orbital moment being no longer well defined, but effectively averaged out. This so-called orbital quenching occurs in many, but not all physical systems. We have developed a non-perturbative relativistic method which allows to calculate the contribution of the orbital part for complex structures [1]. We show that the orbital part actually scales with spin-orbit coupling if orbital quenching is hindered by local symmetry, i.e. in case of dimers or atoms at surfaces. This holds true in particular when the unpaired electron is localized in quasi-atomic p-like orbitals. Here, the orbital part is by far not negligible, but becomes dominant by surpassing the dipolar contribution by a factor of five. It is thus required to achieve overall accuracy in predicting the hyperfine interactions.

[1] Franzke K.L. et al., Relativistic calculation of the orbital hyperfine splitting in complex microscopic structures, accepted in J. Phys. Com., 2023

Keywords: atoms on surfaces; hyperfine splitting; relativistic calculations; DFT; Quantum ESPRESSO