# Localized Plasmons in Topological Insulators

## TL;DR

This paper explores how long-range Coulomb interactions influence topological insulators' excitation spectra, revealing localized plasmonic modes called 'topological plasmons' that depend on the system's topological states and external conditions.

## Contribution

It introduces the concept of topological plasmons in 1D topological insulators and analyzes their properties, protection levels, and tunability via external modifications.

## Key findings

- Localized plasmonic excitations originate from topologically non-trivial states
- Topological plasmons are affected by Coulomb interaction strength
- External dielectric and electric fields can modulate topological plasmons

## Abstract

We investigate in a fully quantum-mechanical manner how the many-body excitation spectrum of topological insulators is affected by the presence of long-range Coulomb interactions. In the one-dimensional Su-Schrieffer-Heeger model and its mirror-symmetric variant strongly localized plasmonic excitations are observed which originate from topologically non-trivial single-particle states. These \textit{"topological plasmons"} inherit some of the characteristics of their constituent topological single-particle states, but they are not equally well protected against disorder due to the admixture of non-topological bulk single-particle states in the polarization function. The strength of the effective Coulomb interactions is also shown to have strong effects on the plasmonic modes. Furthermore, we show how external modifications via dielectric screening and applied electric fields with distinct symmetries can be used to study topological plasmons, thus allowing for experimental verification of our atomistic predictions.