Electron-electron interaction effects on optical excitations in semiconducting single-walled carbon nanotubes

TL;DR

This study uses correlated-electron calculations to analyze how electron-electron interactions influence optical excitations in semiconducting single-walled carbon nanotubes, revealing exciton binding energies and photoluminescence characteristics.

Contribution

It provides detailed insights into exciton binding energies and optical excitation properties considering electron-electron interactions in various nanotube diameters.

Findings

Exciton binding energies decrease with increasing nanotube diameter.

The ratio of second to first exciton energy is smaller than single-particle predictions.

Weak photoluminescence is due to dipole-forbidden excitons below the optical exciton.

Abstract

We report correlated-electron calculations of optically excited states in ten semiconducting single-walled carbon nanotubes with a wide range of diameters. Optical excitation occurs to excitons whose binding energies decrease with the increasing nanotube diameter, and are smaller than the binding energy of an isolated strand of poly-(paraphenylene vinylene). The ratio of the energy of the second optical exciton polarized along the nanotube axis to that of the lowest exciton is smaller than the value predicted within single-particle theory. The experimentally observed weak photoluminescence is an intrinsic feature of semiconducting nanotubes, and is consequence of dipole-forbidden excitons occurring below the optical exciton.