The small slope approximation method applied to a two dimensional dielectric-topological insulator material rough interface

In this paper, the first order perturbation theory (PT) and the small slope approximation (SSA) are employed to analyze the scattering behavior of a two dimensional dielectric-topological insulator (TI) rough interface with Gaussian distribution. Zeroth and first order scattering amplitudes are utilized to obtain the analytic expressions for the coherent and incoherent intensities, respectively. For vertical incidence, an equation can be found whose numerical solution gives the Brewster angle at which the co polarized coherent intensity becomes zero. The scattering scenarios are analyzed where both polarization states of the incident field exhibit total depolarization and the co polarized incoherent scattering is zero.