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O: Fachverband Oberflächenphysik

O 90: Spins on Surfaces at the Atomic Scale II

O 90.1: Vortrag

Donnerstag, 20. März 2025, 15:00–15:15, H11

Relativistic Orbital Effects in Hyperfine Splittings on Surfaces — •Katharina Lorena Franzke, Wolf Gero Schmidt, and Uwe Gerstmann — University of Paderborn Warburger Str. 1 33098 Paderborn

The recent combination of electron spin resonance and scanning tunneling spectroscopy (ESR-STM) provide a new platform to access single spins of atoms and molecules on surfaces [1, 2]. Characteristic hyperfine (hf) splittings due to the interaction between the electronic spin and the magnetic moments of the nuclei can be measured and compared with theoretical predictions from density functional theory (DFT). In comparison with defects in bulk material, however, the calculated data deviates considerably from the experimental values. Limited accuracy of the xc functionals or the direct influence of the electric field of the STM-tip have been discussed as possible reasons.

Large parts of the observed discrepancies however stem from a relativistic effect, the suppression of orbital quenching at surfaces. We developed a fully relativistic method that allows the calculation of this orbital contribution for complex structures [3]. For Pb ions as well as PbPc molecules on the MgO/Ag(111) substrate, this orbital part leads to additional hf splittings in the GHz range and is thereby required to achieve overall accuracy in predicting the hf interactions of single spins in 2D nanostructures.
[1] S. Baumann, et al., Science 350, 417 (2015) [2] L. Farinacci et al., Nano Letters 22, 8470 (2022) [3] K.L. Franzke, et al. J. Phys.: Conference Series. 2701, 012094 (2024)

Keywords: Quantum Espresso; hyperfine splitting; Density Functional Theory; relativistic; orbital quenching