Thesis defence

Title : Impact of Interactions on Magnon Transport

Abstract:
In this Thesis, we investigate how the interactions of magnons affect the transport of electrons and magnons in selected magnetic materials. In particular, we study the impact of the magnon-magnon and the magnon-electron interactions on thetopology and transport in ferromagnets and antiferromagnets. The magnon-magnon interaction has drawn much attention as it can either be detrimental or enhance the properties of topological magnonic systems. We focus on the honeycomb antiferromagnet, which exhibits longitudinal and transverse transport, and we study the effect of multi-magnon interactions on their transport and stability. Furthermore, in magnetic metals, the magnons are expected to interact with electrons, inducing the transfer of momentum and spin between the quasiparticles. This relation hasyet to be deeply investigated, particularly in materials with a non-trivial topology compared to the much-studied phonon-electron interaction. First, we focus on the magnon-electron interaction in ferromagnetic Weyl semimetals, where the transport  is directly interlinked with the topology. We find out that this interaction can bothenhance and destroy topology at higher temperatures. Finally, our focus shifts to a distinct class of magnetic materials with momentum-dependent spin splitting but total magnetization equal to zero, dubbed altermagnets. Altermagnets have drawn  attention because they can be used to generate spin currents efficiently, even in theabsence of spin-orbit coupling. By focusing on the magnon-electron interaction in these materials, we find that electrons that possess altermagnetic splitting can imprint their properties to trivial magnons and induce magnon spin currents with distinct  features. Overall, magnon-magnon and magnon-electron interactions can impact the properties of magnetic materials with heavy  temperature dependence, making their evaluation in materials necessary.

Members of jury:

 

M. AURELIEN MANCHON Aix Marseille Université Thesis Director
M. Alexander MOOK Johannes Gutenberg-Universität Mainz Reviewer
M. Paul MC CLARTY Laboratoire Leon Brillouin, CNRS Reviewer
Ms. Laura MESSIO Sorbonne Université Examiner
Ms. Roser VALENTI Institut für Theoretische Physik, Goethe-Universität Frankfurt am Main Examiner
M. Benoît GRéMAUD Centre de Physique Théorique, CNRS, Aix-Marseille Universite President