Surface plasmon polaritons in topological insulator nano-films and superlattices

We investigate the propagation of surface plasmon polaritons (SPPs) in thin films of topological insulators. Cases of single films and multilayered stacks are analyzed. The materials considered are second generation three dimensional topological insulators Bi₂Se₃, Bi₂Te₃, and Sb₂Te₃. Dispersion relations and propagation lengths of SPPs are estimated numerically, taking into account the variation of bulk dielectric functions of topological insulators, as well as substrate, using the Drude-Lorentz model. The key factors affecting propagation length are identified and experimental modifications for tuning the dispersion relations are proposed. The apparent discrepancy between the experimental data and previously considered theory is resolved.