Strain and screening: Optical properties of a small-diameter carbon nanotube from first principles

TL;DR

This study uses advanced first-principles methods to analyze how strain affects the electronic and optical properties of a small-diameter carbon nanotube, highlighting the role of dielectric screening and atomic geometry.

Contribution

It provides a detailed first-principles analysis of strain effects on CNT optical properties, incorporating quasiparticle and excitonic effects, and extends existing scaling relations to strained systems.

Findings

Strain influences dielectric screening and electronic structure in CNTs.

Accurate first-principles methods can predict optical absorption changes due to strain.

Extended scaling relation effectively describes strained CNT optical properties.

Abstract

Carbon nanotubes (CNTs) are a one-dimensional material system with intriguing physical properties that lead to emerging applications. While CNTs are unusually strain resistant compared to bulk materials, their optical-absorption spectrum is highly strain dependent. It is an open question, as to what extent this is attributed to strain-dependent (i) electronic single-particle transitions, (ii) dielectric screening, or (iii) atomic geometries including CNT radii. We use cutting-edge theoretical spectroscopy to explain strain-dependent electronic structure and optical properties of an (8,0) CNT. Quasiparticle effects are taken into account using Hedin's GW approximation and excitonic effects are described by solving a Bethe-Salpeter-equation for the optical polarization function. This accurate first-principles approach allows us to identify an inuence of strain on screening of the Coulomb electron-electron interaction and to quantify the impact on electronic structure and optical absorption of one-dimensional systems. We interpret our thoroughly converged results using an existing scaling relation and extend the use of this relation to strained CNTs: We show that it captures optical absorption with satisfactory accuracy, as long as screening, quasiparticle gap, and effective electron and hole masses of the strained CNT are known.