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MA: Fachverband Magnetismus
MA 45: Magnetic Relaxation and Gilbert Damping
MA 45.2: Vortrag
Donnerstag, 12. März 2026, 09:45–10:00, POT/0351
Evidence of relativistic field-derivative torque in nonlinear THz response of magnetization dynamics — •Arpita Dutta1, Pratyay Mukherjee6, Swosti P. Sarangi1, Somasree Bhattacharjee6, Christian Tzschaschel2,3, Debankit Priyadarshi3, Kouki Mikuni4, Takuya Satoh4,5, and Ritwik Mondal6 — 1NISER Bhubaneswar, HBNI, Jatni, India — 2Max-Born Institute, Berlin, Germany — 3ETH Zurich, Switzerland — 4Institute of Science Tokyo, Japan — 5Quantum Research Center for Chirality, Okazaki, Japan — 6IIT (ISM) Dhanbad, India
The selective addressing of spins by THz electromagnetic fields via Zeeman torque is one of the most successful means of controlling magnetic excitations. Here, we show that the conventional Zeeman torque on the spin is not sufficient, rather an additional relativistic field derivative torque is essential to realize the observed magnetization dynamics. We accomplish this by exploring the ultrafast nonlinear magnetization dynamics of a ferrimagnetic garnet when excited by two co-propagating THz pulses. Having identified the Kaplan-Kittel mode at 0.48 THz, resulting from the exchange interaction, we drive this to a nonlinear regime. We find that the observed nonlinear trace of the magnetic response cannot be mapped to the magnetization precession induced by the Zeeman torque, while the Zeeman torque supplemented by an additional FDT follows the experimental evidences.
Keywords: Magnon; Ferrimagnets; Terahertz magnetization dynamics; Nonlinear 2D THz spectroscopy