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TT: Fachverband Tiefe Temperaturen

TT 27: Focus Session: Nonlinear Spectroscopy of Collective Excitations in Quantum Magnets (joint session TT/MA)

TT 27.3: Topical Talk

Wednesday, March 19, 2025, 10:30–11:00, H36

Imaging Magnetization Dynamics and Collective Spin Excitations in Compensated Magnets on Ultrafast Timescales — •Benjamin Stadtmüller — Experimentalphysik II, Institute of Physics, Augsburg University, 86159 Augsburg, Germany

Fundamental to the advancement of spintronics and quantum technologies is the ability to encode, manipulate and store information in the spin angular momentum of electrons on ever faster timescales. In this contribution, we therefore discuss the ultrafast magnetic response of compensated magnets, which are interesting candidates for applications due to their robustness against external fields and their fast manipulation speed. We start with the ultrafast magnetization dynamics of conventional antiferromagnets (AFMs), for which the possibility of optical excitation of collective magnon modes on ps timescales has already been demonstrated. For the case of NiO, we show that these timescales can be further reduced by exploiting the strong non-equilibrium excitation with fs laser pulses. These conditions lead to a significant loss of magnetic order and to the excitation of collective magnon modes. We then turn to the ultrafast optical response of the recently discovered class of altermagnets with their d-wave-like spin split band structure. By combining theoretical calculations with ultrafast magneto-optical experiments, we demonstrate the generation of a macroscopic spin polarization in the otherwise fully compensated altermagnet RuO₂, which can additionally be controlled by the excitation geometry [1]. [1] M. Weber and S. Wust et al. arXiv: 2408.05187

Keywords: Ultrafast magnetization dynamics; Antiferromagnets; Altermagnets