Abstract: Electron-magnon interaction from first-principles
The interaction between electrons and magnons can significantly impact the electronic, magnetic and transport properties of numerous systems. Spin fluctuations can lead to a variety of intriguing phenomena, including superconductivity, charge and spin density waves, suppressed or enhanced magnetism, and unusual optical transitions. In my talk, I present a systematic approach to accounting for spin fluctuations and their impact on the electronic structure of magnetic materials [1]. This approach is based on many-body perturbation theory, whereby complex quantities are approximated numerically using quantities from time-dependent density functional theory. The result is a simple, cost-effective algorithm that allows us to study more complex materials than are usually considered in this context (3D ferromagnets), while still accounting for the non-locality of the self-energy. Furthermore, our approach provides a relatively straightforward way to incorporate self-consistency. The method has also been extended to anti-Stoner excitations, which arise from a spin flip whereby an electron is effectively promoted from a minority to a majority spin state. This complements Stoner excitations and spin waves. I will discuss our recent studies on spin fluctuations in CeCo₂P₂ and LaCo₂P₂ by way of example [2, 3]. These materials consist of ferromagnetic layers that are weakly coupled via ferromagnetic or antiferromagnetic interactions. The electron-magnon interaction in these materials induces strong electronic structure renormalisation. In turn, a specific electronic structure ensures the persistence of spin waves.
[1] S. Paischer et al., Nonlocal correlation effects due to virtual spin-flip processes in itinerant electron ferromagnets, Phys. Rev. B 107, 134410 (2023)
[2] S. Paischer et al., Electronic correlations arising from anti-Stoner spin excitations: An ab initio study of itinerant ferro- and antiferromagnets, Phys. Rev. B 110, 165121 (2024)
[3] G. Poelchen et al., Long-lived spin waves in a metallic antiferromagnet, Nature Communications 14, 5422 (2023)
[4] D. Yu. Usachov et al., Insight into the electron-boson coupling in ferromagnet LaCo2P2, Advanced Physics Research, 240013 (2024)
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