Control of Plasmons in Topological Insulators via Local Perturbations

TL;DR

This paper demonstrates how molecule-scale perturbations can control localized plasmonic excitations in topological insulators, affecting their energies and charge distributions through a quantum mechanical approach.

Contribution

It introduces a quantum mechanical method to manipulate surface plasmons in topological insulators using local perturbations, revealing effects on energy levels and charge transfer.

Findings

Localized surface plasmons are influenced by molecular perturbations.

Perturbations can shift plasmon energies and alter charge density profiles.

Conditions for significant charge transfer are identified.

Abstract

We use a fully quantum mechanical approach to demonstrate control of plasmonic excitations in prototype models of topological insulators by molecule-scale perturbations. Strongly localized surface plasmons are present in the host systems, arising from the topologically non-trivial single-particle edge states. A numerical evaluation of the RPA equations for the perturbed systems reveals how the positions and the internal electronic structure of the added molecules affect the degeneracy of the locally confined collective excitations, i.e., shifting the plasmonic energies of the host system and changing their spatial charge density profile. In particular, we identify conditions under which significant charge transfer from the host system to the added molecules occurs. Furthermore, the induced field energy density in the perturbed topological systems due to external electric fields is determined.