Dresden 2026 – scientific programme
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MA: Fachverband Magnetismus
MA 27: Ultrafast Magnetization Effects I
MA 27.1: Invited Talk
Wednesday, March 11, 2026, 09:30–10:00, HSZ/0004
Towards sub-10fs magnetization switching — Reza Rouzegar1, Oliver Franke1, Gal Lemut1, Oliver Gueckstock1, Junwei Tong1, Dieter Engel2, Xianmin Zhang3, Georg Woltersdorf4, Piet W. Brouwer1, Tobias Kampfrath1, and •Quentin Remy1 — 1Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany — 2Max-Born-Institut für nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany — 3Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Material Science and Engineering, Northeastern University, Shenyang 110819, China — 4Institut für Physik, Martin-Luther-Universität Halle, 06120 Halle, Germany
Femtosecond laser pulses can induce sub-picosecond demagnetization, enabling ultrafast magnetic writing, spin transport, and broadband THz generation. Yet the microscopic processes in the first ~ 10 fs remain poorly understood. Three-temperature models describe energy flow among electrons, spins, and the lattice but neglect angular-momentum transfer, essential for spin dissipation.
Using ultrabroadband THz emission spectroscopy with ~ 10 fs resolution, we find that electron-magnon (em) scattering drives the nonequilibrium spin dynamics, generating both spin flips and magnons in under 10 fs, well before ~ 100 fs demagnetization. Angular momentum is then dissipated primarily through magnon-lattice interactions. Having established em scattering as the dominant sub-10-fs mechanism, we show that THz pulses can harness this coupling to reverse magnetization, pointing to sub-10-fs spin control.
Keywords: Demagnetization; Magnons; THz emission; Switching; Nonequilibrium