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.

Ion implantation in diamond creates optically active defects which have emission lines in broad spectral regions, and may be used in advanced photonics and optical communication applications. A brief review of the photoluminescence properties of Xe + ion implanted diamond is presented. The Xe-related center is of particular interest as this center is one of a few centers (Ni, Si, Cr) in diamond having sharp emission lines in the infrared spectral region, specifically at 813 and 794 nm. The paper discusses an approach to determine an important and difficult to measure conversion efficiency of implanted ions into emitting optical centers. The method uses a micro-luminescence confocal mapping and statistical analysis based on a compound Poisson distribution, accounting for both the implanted centers and the optically excited centers statistics. Results of numerical simulations and experimental measurements are presented.PACS: 78.55.-m Photoluminescence, properties and matherials; 73.20.Hb Impurity and defect levels; energy states of adsorbed species.

Robustness to disorder is the defining property of any topological state. The ultimate disorder limits to topological protection are still unknown, although a number of theories predict that even in the amorphous state a quantized conductance might yet reemerge. Here we report that in strongly disordered thin films of the topological material Sb 2 Te 3 disorder-induced spin correlations dominate transport of charge-they engender a spin memory phenomenon, generated by the nonequilibrium charge currents controlled by localized spins. We directly detect a glassy yet robust disorder-induced magnetic signal in films free of extrinsic magnetic dopants, which becomes null in a lower-disorder crystalline state. This is where large isotropic negative magnetoresistance (MR)-a hallmark of spin memory-crosses over to positive MR, first with only one e 2 /h quantum conduction channel, in a weakly antilocalized diffusive transport regime with a 2D scaling characteristic of the topological state. A fresh perspective revealed by our findings is that spin memory effect sets a disorder threshold to the protected topological state. It also points to new possibilities of tuning spin-dependent charge transport by disorder engineering of topological materials.

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