Spin friction of single atoms investigated by scanning tunneling microscopy

• Applicant: Dr. André Kubetzka
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 408119516

Atom manipulation with the tip of a scanning tunneling microscope (STM) is a widespread and straightforward technique to build complex nanostructures in an atom-by-atom fashion. In this project I want to use atom manipulation as an imaging tool to investigate the static and dynamic properties of adatoms on magnetic surfaces. Instead of measuring (spin-dependent) density of states a few atomic distances above the surface, as in standard (spin-polarized) STM, the manipulated adatom can be seen as an extension of the tip probing (spin-dependent) forces right at the surface. The central question of this project is the following: Which interactions influence an adatom's path when it is moved across a magnetic surface? Here, I am especially interested in magnetic interactions beyond the nearest neighbor Heisenberg exchange. Closely related to this question are the aspects of energy dissipation and friction, and to what extend the spin degree of freedom plays a role in these processes. To disentangle different contributions, especially the magnetic from the electronic ones, I will use magnetic as well as non-magnetic tips and adatoms on a variety of surface spin textures such as antiferromagnets, spin spirals, skyrmion lattices and domain walls. Since the manipulation experiments can reveal site-dependent binding strengths of adatoms, it should be possible to estimate to what extent magnetism can influence adatom diffusion and thus growth processes in general. Additional atom diffusion experiments are planned to verify this idea. Furthermore, in cases where the resting or moving adatom acts back onto the local surface spin texture, I will try and exploit this effect to control magnetic states with manipulated ensembles of adatoms.

• DFG Programme: Research Grants