Effect of molecular-scale perturbations on Plasmons in Topological Insulators

We develop and apply a fully quantum mechanical approach to analyze the plasmonic excitation spectrum in the Su-Schrieffer-Heeger (SSH) model and its mirror symmetric(m-SSH) in the presence of molecule-scale perturbations. Strongly localized plasmons are observed in the host system due to the topological non-trivial single-particle edge states. Numerical evaluation of the RPA equations for the perturbed system show how the strength and position of the added impurities have strong effects on the degeneracy of localized collective excitations, i.e. the plasmonic energies shift and the spatial charge modulations change due to the perturbation. Furthermore, the plasmonic response to external electric fields is determined, which can be verified experimentally.