Prof. Dr. Mathias Kläui
Prof. Dr. Mathias Weiler
2D systems exhibit real-space topological phases and phase transitions that do not exist in 3D systems.
Topologically stabilized non-trivial 2D skyrmion spin structures are a particularly appealing system to study
such phase transitions. In particular, skyrmions have - in contrast to previously studied rigid colloids - complex
internal degrees of freedom that could be exploited to affect phases and phase transitions. Such 2D skyrmions
have been found to exist in thin film metallic magnets with strong interfacial Dzyaloshinskii-Moriya
interaction and the formation of lattices has been recently observed in these systems.
Here, we propose to manipulate and control the skyrmion lattice formation dynamics in such thin film metallic
magnets by uniform and non-uniform magnetic excitations. Going beyond the state-of-the-art, where skyrmion
lattice formation is initiated by a uniform magnetic field pulse and takes place on the timescale of ms to
seconds, we here will experimentally study the phase transition under alternating uniform and non-uniform
magnetic excitations. We thereby want to understand to what extent the skyrmion lattice formation dynamics
can be controlled by the application of tailored magnetic field landscapes. To this end, we will (i) excite
magnetic eigenmodes that change the shape of the individual particles and (ii) use lateral excitation by
magnetic field gradients and spin waves. We expect that these excitations can be used to overcome local energy
maxima and thus lead to an enhanced skyrmion lattice formation. Our experiments will be carried out by
combining alternating magnetic field gradients and microwave excitations with Kerr microscopy to image the
skyrmion lattice formation dynamics.
This work takes advantage of the complementary expertise of the two PIs with Prof. Kläui specializing in
imaging of skyrmion phases and Prof. Weiler contributing extensive experience in the dynamic excitation of
skyrmions. The work is embedded in the exploratory areas EA1 (real-space topology) with dynamical aspects
reaching out to EA4. We thus expect collaborations with other TopDyn members working with skyrmions and
also with colleagues studying the lattice phase transitions in other systems, such as cold atoms.