A key challenge in spintronics is to efficiently generate and manipulate spin current for information processing. Here we study ultrashort spin transport and associated terahertz (THz) emission in a hybrid structure comprising gold nanoparticles, a ferromagnet (FM) and a normal metal (NM) and show that plasmon excitation in the nanoparticles strongly enhances the electron-magnon scattering rate through heating effects, thereby amplifying the spin current generation at the FM∣NM interface. This effect is even more pronounced when the FM is an insulator with a thickness much smaller than the nanoparticle size. In this case, the gold nanoparticle and NM substrate form a nanocavity with the FM as a dielectric layer, trapping plasmons inside the gap. The resulting spin current can be amplified by two orders of magnitude as compared to the case without plasmon excitations. Our findings provide a novel route to design efficient spintronic THz devices and further open the door to the interdisciplinary field of spintronics and nanophotonics.
@article{arxiv.2505.18045,
title = {Plasmon-Driven Giant Amplification of Ultrashort Spin Current},
author = {H. Y. Yuan and Rembert A. Duine},
journal= {arXiv preprint arXiv:2505.18045},
year = {2025}
}