Berlin 2024 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 20: Poster I
MA 20.2: Poster
Dienstag, 19. März 2024, 16:30–19:00, Poster A
Dynamical Renormalization of a Spin Hamiltonian via High-order Nonlinear Magnonics — •Julian Bär1, Christoph Schönfeld1, Lennart Feuerer1, Alfred Leitenstorfer1, Dominik Juraschek2, and Davide Bossini1 — 1Department of Physics, University of Konstanz, D-78457 Konstanz, Germany — 2School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
A key question of the research field of ultrafast magnetic phenomena addresses the generation and control of magnons on fundamental timescales. Standard approaches involve resonant or non-resonant excitation of low-frequency one-magnon modes. High-frequency pairs of magnons near the edges of the Brillouin zone have also been non-resonantly induced. However, most studies disclosed spin dynamics, which are described by linear spin-wave theory. Our work utilizes a high-field laser source in the multi-THz regime to directly excite zone-edge magnons in Hematite. This pumping scheme induces an unexplored magnetic excited state. Theoretical predictions suggest that this excited state can result in strongly nonlinear magnetic phenomena. By tuning the photon energy of the mid-infrared laser, we investigate the spin dynamics induced both via resonant and non-resonant excitation of the two-magnon mode. Experimental results demonstrate coherent coupling between photo-driven high-energy magnons and zone-center modes. The photoexcitation drives the system to an extreme nonequilibrium state, significantly altering the spectrum of zone-center modes. These findings highlight the potential to manipulate the magnonic dispersion on femtosecond timescales through purely magnetic processes.
Keywords: Ultrafast Magnonics; Antiferromagnets; Nonlinear Magnonics; Ultrafast Physics; Mid-Infrared Laser