Role of subcycle transition dynamics in high-order-harmonic generation in periodic structures

In this paper a method is presented for calculating the subcycle rate for transitions of electrons between two bands of a sinusoidal band structure. A simple closed-form expression for the rate is derived. We show that transition dynamics are sensitive to the shape of the band structure away from the minima of the conduction band. A model of high-order-harmonic generation in periodic solids that incorporates the subcycle dynamics of transitions across the band gap is described. Harmonic emission is found to be highly sensitive to the temporal shape of the transition rate. Destructive interference of electron currents in the conduction band due to subcycle transition dynamics is described.