Exact solution for high harmonic generation and the response to an ac driving field for a charge density wave insulator

摘要

We develop and exactly solve a model for electrons driven by pulsed orcontinuous ac fields. The theory includes both the photoexcitation process aswell as the subsequent acceleration of the electrons. In the case of an acresponse, we examine both the nonequilibrium density of states and the current.In the case of pulsed light for high harmonic generation, we find the radiatedlight assumes a nearly universal behavior, with only limited dependence on theparameters of the system, except for the amplitude of the driving field, whichdetermines the range of high harmonics generated and a tendency toward anarrowing of the peaks in a charge density wave versus a metal. This type ofhigh harmonic generation can potentially be used for the creation ofsolid-state-based ultrafast light sources.