Exchange-enhanced Ultrastrong Magnon-Magnon Coupling in a Compensated Ferrimagnet
Abstract
The ultrastrong coupling of (quasi-)particles has gained considerable attention due to its application potential and richness of the underlying physics. Coupling phenomena arising due to electromagnetic interactions are well explored. In magnetically ordered systems, the quantum-mechanical exchange-interaction should furthermore enable a fundamentally different coupling mechanism. Here, we report the observation of ultrastrong intralayer exchange-enhanced magnon-magnon coupling in a compensated ferrimagnet. We experimentally study the spin dynamics in a gadolinium iron garnet single crystal using broadband ferromagnetic resonance. Close to the ferrimagnetic compensation temperature, we observe ultrastrong coupling of clockwise and anticlockwise magnon modes. The magnon-magnon coupling strength reaches more than 30% of the mode frequency and can be tuned by varying the direction of the external magnetic field. We theoretically explain the observed phenomenon in terms of an exchange-enhanced mode-coupling mediated by a weak cubic anisotropy.
Keywords
Cite
@article{arxiv.1903.04330,
title = {Exchange-enhanced Ultrastrong Magnon-Magnon Coupling in a Compensated Ferrimagnet},
author = {Lukas Liensberger and Akashdeep Kamra and Hannes Maier-Flaig and Stephan Geprägs and Andreas Erb and Sebastian T. B. Goennenwein and Rudolf Gross and Wolfgang Belzig and Hans Huebl and Mathias Weiler},
journal= {arXiv preprint arXiv:1903.04330},
year = {2019}
}