Dresden 2026 – scientific programme

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MA: Fachverband Magnetismus

MA 7: Poster Magnetism I

MA 7.11: Poster

Monday, March 9, 2026, 09:30–12:30, P2

Coupled Magnon-Phonon Dynamics: From Ab Initio Boltzmann Transport to the Three-Temperature Model — •Philipp Rieger, Markus Weissenhofer, and Peter M. Oppeneer — Uppsala University, Uppsala, Sweden

The ultrafast transfer of angular momentum and heat between spin and lattice subsystems is key to spintronics, recently demonstrated to occur on sub-picosecond timescales [1]. While the Three-Temperature Model (3TM) remains a cornerstone for describing this ultrafast demagnetization, its crucial spin-lattice coupling parameter, G_sl, typically relies on empirical fitting [2]. To address this, we developed an atomistic framework [3,4] that solves the coupled magnon-phonon Boltzmann transport equation based solely on ab initio inputs. Applied to bcc Fe and fcc Ni, we resolve real-time mode-level dynamics, transport properties, and quasiparticle lifetimes. Crucially, we demonstrate for the first time that the macroscopic 3TM spin-lattice coupling emerges as a valid linear approximation of the underlying non-thermal microscopic dynamics. Consequently, we derive a first-principles G_sl that reproduces the seminal results of Beaurepaire et al. [2], unifying the microscopic and phenomenological descriptions of ultrafast spin-lattice dynamics. [1] S. R. Tauchert et al., Nature 602, 73–77 (2022)
[2] E. Beaurepaire et al., PRL 76, 4250 (1996)
[3] S. Mankovsky et al., PRL 129, 067202 (2022)
[4] M. Weissenhofer, P. Rieger et al., PRL 135, 216701 (2025)

Keywords: Spin-Lattice Coupling; Ultrafast Demagnetization; spintronics; Boltzmann dynamics; magnon-phonon dynamics