Effect of surface states on scattering from a slab made of topological insulator material with rough interface

Using the perturbation theory (PT), reflected field both in specular and non specular directions from a slab made of topological insulator (TI) material with rough interface is studied. The specular reflections are described by zeroth order terms of the perturbation series while non specular reflections are associated with higher order terms. To describe the surface states on the TI, gamma-model characterized by the surface admittance is utilized. It is observed that the co-polarized specular reflection increases for large values of surface admittance which results in vanishing transmission. The main objective is to pronounce distinctions between the results for a dielectric slab and TI slab. It is observed that the co polarized diffraction efficiency of the sinusoidal grating is enhanced for p-polarization as the surface admittance increases. Moreover, the scattering behavior of the TI slab with Gaussian rough interface as a function of surface admittance differs significantly from that of the dielectric slab.