Ultrafast Spectroscopy of Mid-Infrared Internal Exciton Transitions of Separated Single-Walled Carbon Nanotubes

TL;DR

This study uses femtosecond mid-infrared spectroscopy to investigate intra-excitonic transitions in separated single-walled carbon nanotubes, revealing detailed excitonic dynamics and saturation effects.

Contribution

It provides the first detailed ultrafast spectroscopic analysis of intra-excitonic transitions in separated nanotubes, with a model explaining the observed signals.

Findings

Observation of strong photoinduced absorption at 200 meV

Identification of quasi-1D intra-excitonic transitions

Saturation of absorption with phase-space filling

Abstract

We report a femtosecond mid-infrared study of the broadband low-energy response of individually separated (6,5) and (7,5) single-walled carbon nanotubes. Strong photoinduced absorption is observed around 200 meV, whose transition energy, oscillator strength, resonant chirality enhancement and dynamics manifest the observation of quasi-1D intra-excitonic transitions. A model of the nanotube 1s-2p cross section agrees well with the signal amplitudes. Our study further reveals saturation of the photoinduced absorption with increasing phase-space filling of the correlated e-h pairs.