Electron-induced nonlinear dynamics in atomic chains

We study the nonlinear response of collective optical resonances in linear atomic chains with metallic, semiconducting, and topologically insulating character to low-energy free electrons. The nonlinearity, which manifests in the amplitude and frequency of resonant features in cathodoluminescence and electron energy-loss spectra, is shown to depend on the speed and trajectory of the excitation as well as the length and electronic structure of the chain. Time-domain analysis of charge carrier dynamics within the atomic chain reveals that the Fermi velocity sets the threshold speed for triggering an electron-induced nonlinear response, a phenomenon which can elucidate nonlinear light-matter interactions on the nanoscale.