Radiative Lifetime of Excitons in Carbon Nanotubes

TL;DR

This paper models the radiative lifetime of excitons in semiconducting carbon nanotubes, revealing how temperature, diameter, and symmetry-breaking effects influence exciton decay rates.

Contribution

It provides a detailed theoretical analysis of exciton radiative lifetimes considering intrinsic and extrinsic effects in carbon nanotubes.

Findings

Radiative lifetime peaks at intermediate temperatures.

Optically forbidden excitons dominate at low temperatures.

Extrinsic symmetry-breaking effects significantly impact exciton decay.

Abstract

We calculate the radiative lifetime and energy bandstructure of excitons in semiconducting carbon nanotubes, within a tight-binding approach. In the limit of rapid interband thermalization, the radiative decay rate is maximized at intermediate temperatures, decreasing at low temperature because the lowest-energy excitons are optically forbidden. The intrinsic phonons cannot scatter excitons between optically active and forbidden bands, so sample-dependent extrinsic effects that break the symmetries can play a central role. We calculate the diameter-dependent energy splittings between singlet and triplet excitons of different symmetries, and the resulting dependence of radiative lifetime on temperature and tube diameter.