Photoengineering the magnon spectrum in an insulating antiferromagnet
V. Radovskaia (Radboud Universiteit Nijmegen)
R. Andrei (ETH Zürich)
J. R. Hortensius (TU Delft - BUS/TNO STAFF, Kavli institute of nanoscience Delft, TNO)
R. V. Mikhaylovskiy (Lancaster University)
R. Citro (University of Salerno)
S. Chattopadhyay (ETH Zürich, Harvard University)
B. A. Ivanov (Radboud Universiteit Nijmegen, National Academy of Sciences of Ukraine )
A. D. Caviglia (Université de Genève, TU Delft - Applied Sciences)
D. Afanasiev (Radboud Universiteit Nijmegen)
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Abstract
In antiferromagnets, where quantum mechanical exchange interactions dictate spin behaviour, understanding the dynamics of magnons—collective spin wave excitations that naturally reach terahertz frequencies and supersonic velocities—is essential for both fundamental science and emerging technologies. Femtosecond optical pulses offer a powerful means to coherently excite these magnons across the full Brillouin zone and to manipulate their spectral characteristics. Yet, achieving such control has remained difficult, as it requires ultrafast and sustained tuning of the underlying exchange interaction. Here we demonstrate an optically driven renormalization of the terahertz magnon spectrum in the insulating antiferromagnet DyFeO₃. Our results show that this transformation arises from a substantial transient reduction of the exchange interaction within a nanoscale region near the surface. These findings reveal a route to light-induced, nanoscale control of antiferromagnetic spin dynamics, opening opportunities for reconfigurable, ultrafast magnonic and spintronic functionalities.