Magnon-electron scattering and non-Landau magnon decay, ab initio theories

This habilitation treatise is concerned with the description of the spin dynamics in solids using linear response time-dependent density functional theory going beyond the ferromagnetic spin waves. First, the application of the method to ferri- and antiferromagnets is presented. Following this, the studies of paramagnons and longitudinal spin excitations are outlined. Following this, the non-Landau magnon decay channels, in particular disorder and multi-magnon processes, are assessed in order to establish the hierarchy of the spin dynamics attenuation in itinerant magnets. In the second part, the theory of magnon-electron interaction based on the time-dependent density functional theory is exposed and applied to several relevant magnetic systems. This interaction leads to a range of measurable and important phenomena, including band structure renormalization, the emergence of non-quasiparticle states, the unconventional superconducting pairing, and the impact on the spin dynamics itself, which are addressed from an ab initio perspective.