Spin-orbit coupling induced ultrahigh-harmonic generation from magnetic dynamics

The generation of a nonlinear high-frequency response in solids from powerful optical pumps has gained momentum over the past decade. High-harmonic generation (HHG) in solids can be obtained from strong-field laser excitation, usually restricted to optical frequencies and limited both in amplitude and in harmonic order. Here, we demonstrate that high-harmonic emission can be achieved by exploiting conventional spin pumping, without the need for optical excitation. Considering a noncentrosymmetric (ferro- or antiferro-)magnet excited at a frequency ω, we demonstrate the emergence of HHG in two main regimes: (i) In the perturbative regime, where a weak spin-orbit interaction is considered, the carrier pumping features a number of harmonics with a cutoff order nmax