Abstract
The generation of nonlinear high-frequency response in solids from powerful optical pumps has gained momentum over the past decade. High-harmonic generation 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, we show that when the spin-orbit coupling strength is close to the s-d exchange energy, a strongly nonlinear regime resulting from resonant spin flip scattering occurs leading to the generation of a large number of harmonics at realistic precession frequencies, thereby enhancing both spin and charge dynamics by orders of magnitude. This mechanism could be used to trigger high-frequency emission deep in the THz regime.