The application of topology to characterize the states of condensed matter is an extremely active field today, illustrated by the tremendous recent work on topological insulators, topological Dirac and Weyl semimetals, and magnetic skyrmion phases. The robustness of topologically nontrivial states is guaranteed by a non-zero topological invariant, which often gives rise to fascinating new physical phenomena like the spin-momentum locking in surface states of topological insulators, the quantum anomalous Hall effect, the chiral anomaly or the topological Hall effect. In addition to being fundamentally interesting, topological protection makes topological states desirable for applications, for example in quantum computing or skyrmion-based spintronic devices.

In this project, we are going to study magnetic materials with nontrivial topology characterizing either the ground state or the collective excitations. In this experimental PhD project, we aim to use time-domain and Fourier transform THz spectroscopy to study the spin dynamics of such magnets. The spectroscopy of the spin excitations will provide valuable information about the magnetic interactions often competing with each other. The applicant will study materials with complex ordering patterns such as spirals, skyrmion, half-skyrmion lattice phases or entangled spin-dimers. Part of the work will be carried out at large scale facilities as a part of on-going international collaboration.