Investigation of the hyperfine interaction of single atoms in a vector magnetic field*

The combination of electron spin resonance and scanning tunnelling microscopy gives exceptional energy resolution for the investigation of spin-spin interactions on the atomic level [1]. Remarkably, Willke et al. measured the hyperfine interaction of individual atoms on MgO/Ag(001) [2]. They showed that the hyperfine interaction is strongly dependent on the binding site of the investigated atoms, resulting from variations in the electronic ground state of the atoms as well as on various other properties such as the level of mixing with neighbouring atoms and the spatial extent of the nuclear spin wave-function. Here, we provide a full angle-dependent investigation of the measured hyperfine splitting for Ti on MgO/Ag(001) through measurements in a vector magnetic field. We observe a strong anisotropy of the interaction that can be related to the anisotropy of the g-factor which has been highlighted in other studies [3,4]. This gives us unprecedented insight into the electronic ground state configuration of the atoms.

 

[1] S. Baumann et al., Science 350, 6259 (2015)

[2] P. Willke et al., Science 362, 336 (2018)

[3] M. Steinbrecher et al., Phys. Rev. B 103, 155405 (2021)

[4] J. Kim et al., arXiv:2103.09582 (2021)