Excitons in carbon nanotubes: an ab initio symmetry-based approach

TL;DR

This paper presents an ab initio symmetry-based method to compute excitonic effects in carbon nanotubes, providing detailed insights into exciton properties and optical spectra with improved computational efficiency.

Contribution

A new local basis set method respecting tube symmetry is developed, enabling faster scaling and precise symmetry analysis of excitonic states in nanotubes.

Findings

Exciton binding energy is approximately 0.8 eV.

Exciton wavefunctions are delocalized circumferentially and localized axially.

Method improves computational efficiency over plane-wave approaches.

Abstract

The optical absorption spectrum of the carbon (4,2) nanotube is computed using an ab-initio many-body approach which takes into account excitonic effects. We develop a new method involving a local basis set which is symmetric with respect to the screw symmetry of the tube. Such a method has the advantages of scaling faster than plane-wave methods and allowing for a precise determination of the symmetry character of the single particle states, two-particle excitations, and selection rules. The binding energy of the lowest, optically active states is approximately 0.8 eV. The corresponding exciton wavefunctions are delocalized along the circumference of the tube and localized in the direction of the tube axis.