Excitons in single-walled carbon nanotubes: environmental effect

TL;DR

This paper models how the dielectric environment affects exciton properties in single-walled carbon nanotubes, showing that surrounding media significantly influence exciton binding energies and optical spectra.

Contribution

It introduces a potential model to analyze environmental effects on excitons in SWCNTs, aligning theoretical results with experimental data for various permittivities.

Findings

Exciton binding energies vary with environmental permittivity.

Low permittivity environments lead to exciton binding energies exceeding energy gaps.

Results agree with experimental data for permittivities above 4.

Abstract

The properties of excitons in semiconducting single-walled carbon nanotubes (SWCNTs), isolated in vacuum or a medium, and their contributions to the optical spectra of nanotubes are studied within the elementary potential model, in which an exciton is represented as a bound state of two oppositely charged quasi-particles confined to the nanotube surface. The emphasis is given on the influence of dielectric environment surrounding a nanotube on the exciton spectra. For nanotubes in environment with permittivity less than 1.8 the ground-state exciton binding energies exceed the respective energy gaps, while the obtained binding energies of excitons in nanotubes in a medium with permittivity greater than 4 are in good accordance with the corresponding experimental data and consistent with known scaling relation for the environmental effect. The stabilization process of single-electron spectrum in SWCNTs in media with rather low permittivities is discussed.