Intersubband decay of 1-D exciton resonances in carbon nanotubes

TL;DR

This study investigates the decay mechanisms of E22 excitons in semiconducting carbon nanotubes, combining experimental photoluminescence data with theoretical Bethe-Salpeter calculations to understand linewidth behaviors and decay pathways.

Contribution

It provides a combined experimental and theoretical analysis of intersubband decay in carbon nanotubes, revealing phonon-assisted decay processes and energy-dependent linewidth behaviors.

Findings

Linewidths increase with energy regardless of family affiliation.

Phonon-assisted coupling dominates exciton decay pathways.

Decay into exciton bands is roughly ten times more likely than into free carrier bands.

Abstract

We have studied intersubband decay of E22 excitons in semiconducting carbon nanotubes experimentally and theoretically. Photoluminescence excitation line widths of semiconducting nanotubes with chiral indicess (n, m) can be mapped onto a connectivity grid with curves of constant (n-m) and (2n+m). Moreover, the global behavior of E22 linewidths is best characterized by a strong increase with energy irrespective of their (n-m) mod(3)= \pm 1 family affiliation. Solution of the Bethe-Salpeter equations shows that the E22 linewidths are dominated by phonon assisted coupling to higher momentum states of the E11 and E12 exciton bands. The calculations also suggest that the branching ratio for decay into exciton bands vs free carrier bands, respectively is about 10:1.