Localized Plasmons in Topological Insulators

We investigate in a fully quantum-mechanical manner how the many-body excitation spectrum of topological insulators are affected by the presence of long-range Coulomb interactions. We show how special and highly localized plasmonic excitations partially result from non-trivial topological single-particle states of the one-dimensional Su-Schrieffer-Heeger model and study how these states inherit some of the topological characteristics of their constituent single-particle origin. Since these \textit{``topological plasmon"} modes are generated by mixing topological edge with non-topological bulk single-particle states, they are not equally well protected against disorder and show a less stable excitation energy and localization. Furthermore, we show how external modifications via dielectric screening or applied electric fields with distinct symmetries can be used to study these topological plasmons allowing for experimental verification of our atomistic predictions.