Self-consistent Floquet states for periodically driven quantum wells

We have developed a nonperturbative method to compute the dynamics of electrons in quantum wells driven by oscillating electric fields. Floquet theory enables us to compute, in the local-density approximation, solutions of the Schrödinger equation for zero temperature which are self-consistent and for which the density is periodic in time. The method is demonstrated by computing harmonic generation from a tilted square well, which agrees with perturbation theory, and second-harmonic emission from an ${\mathrm{Al}}_{0.3}$${\mathrm{Ga}}_{0.7}$As heterojunction, which agrees with recent experiments of Bewley et al.