# Plasmonics of Topological Insulators at Optical Frequencies

## TL;DR

This paper investigates the plasmonic properties of topological insulators, revealing their potential as low-loss plasmonic media across a broad optical spectrum, including visible, UV, and mid-infrared ranges.

## Contribution

It provides a first-principles analysis of dielectric functions of topological insulators, demonstrating their superior plasmonic response compared to traditional metals like gold and silver.

## Key findings

- Topological insulators exhibit strong plasmonic response from 2-3 eV extending to higher frequencies.
- These materials outperform gold and silver in the blue and UV spectral ranges.
- Surface states support propagating plasmon polariton modes over a broad spectral range.

## Abstract

The development of nanoplasmonic devices, such as plasmonic circuits and metamaterial superlenses in the visible to ultraviolet frequency range, is hampered by the lack of low-loss plasmonic media. Recently, strong plasmonic response was reported in a certain class of topological insulators. Here, we present a first-principles density functional theory analysis of the dielectric functions of topologically insulating quaternary (Bi,Sb)2(Te,Se)3 trichalcogenide compounds. Bulk plasmonic properties, dominated by interband transitions, are observed from 2-3 eV and extend to higher frequencies. Moreover, trichalcogenide compounds are better plasmonic media than gold and silver at blue and UV wavelengths. By analysing thin slabs, we also show that these materials exhibit topologically protected surface states, which are capable of supporting propagating plasmon polariton modes over an extremely broad spectral range, from the visible to the mid-infrared and beyond, owing to a combination of inter- and intra-surface band transitions.

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Source: https://tomesphere.com/paper/1702.00302