Independence of Optical Absorption on Auger Ionization in Single-Walled Carbon Nanotubes Revealed by Ultrafast e-h Photodoping

TL;DR

This study demonstrates that Auger-ionized excitons in single-walled carbon nanotubes do not disassociate during high-intensity laser irradiation, revealing that optical absorption remains unaffected by Auger ionization, contrary to previous predictions.

Contribution

The paper provides experimental evidence that Auger-ionized excitons in SWCNTs stay bound, challenging the expectation of strong band-gap renormalization due to ionization.

Findings

Auger-ionized excitons remain bound in SWCNTs.

Optical absorption is independent of Auger ionization.

No significant band-gap renormalization observed.

Abstract

Auger-ionized carriers in a one-dimensional semiconductor are predicted to result in a strong band-gap renormalization. Isolated single-walled carbon nanotubes (SWCNT) under high-intensity laser irradiation exhibit strong nonlinear photoluminescence (PL) due to exciton-exciton annihilation (EEA). The presence of exciton disassociation during the rapid Auger-ionization caused by EEA would lead to a strong nonlinear absorption. By simultaneously measuring SWCNT PL and optical absorption of isolated SWCNT clusters in the PL saturation regime, we give evidence that Auger-ionized excitons do not disassociate but remain bound.