Nonlinear THz response of a one-dimensional superlattice

The dynamics of an electron in a one-dimensional superlattice is investigated under the action of a THz electric field. The density matrix equations of motion within a single miniband are solved using a relaxationtime approximation for scattering. The electronic response to THz radiation is obtained by calculating the dipole moment, whence we compute the power dissipated, the THz reflection coefficient and dipole radiation. Collisions are essential in eliminating transients and bringing the electron in phase with the field at dynamic localization. The optical properties of the superlattice bear strong signatures of dynamic electron localization such as oscillations with varying field strengths. In addition, the response is multivalued in the incident field owing to the nonlinear relation between the incident and internal fields of the superlattice. The optical properties are robust with respect to the inclusion of higher harmonics, weak collisions, and deviations from a tight-binding miniband dispersion.