The propagation of spin waves in magnetically ordered systems has emerged as a potential means to shuttle quantum information over large distances. Conventionally, the arrival time of a spin wavepacket at a distance, d, is assumed to be determined by its group velocity, vg. He we report time-resolved optical measurements of wavepacket propagation in the Kagome ferromagnet Fe3Sn2 that demonstrate the arrival of spin information at times significantly less than d/vg. We show that this spin wave "precursor" originates from the interaction of light with the unusual spectrum of magnetostatic modes in Fe3Sn2. Related effects may have far-reaching consequences toward realizing long-range, ultrafast spin wave transport in both ferromagnetic and antiferromagnetic systems.
@article{arxiv.2212.02498,
title = {Spin wavepackets in the Kagome ferromagnet Fe$_3$Sn$_2$: propagation and precursors},
author = {Changmin Lee and Yue Sun and Linda Ye and Sumedh Rathi and Kevin Wang and Yuan-Ming Lu and Joel Moore and Joseph G. Checkelsky and Joseph Orenstein},
journal= {arXiv preprint arXiv:2212.02498},
year = {2023}
}