Biexciton, single carrier, and trion generation dynamics in single-walled carbon nanotubes

TL;DR

This study investigates the generation and dynamics of biexcitons, trions, and free carriers in semiconducting single-walled carbon nanotubes using ultrafast spectroscopy, revealing strong Coulomb interactions and carrier recombination processes.

Contribution

It provides new insights into the formation and decay mechanisms of multi-carrier states in carbon nanotubes under ultrafast excitation.

Findings

Biexciton binding energy is 130 meV.

Trion formation involves a binding energy of 190 meV.

High-density excitation leads to Auger processes expelling carriers.

Abstract

We present a study of free carrier photo-generation and multi-carrier bound states, such as biexcitons and trions (ionized excitons), in semiconducting single-walled carbon nanotubes. Pump-and-probe measurements performed with fs pulses reveal the effects of strong Coulomb interactions between carriers on their dynamics. Biexciton formation by optical transition from exciton population results in an induced absorption line (binding energy 130 meV). Exciton-exciton annihilation process is shown to evolve at high densities towards an Auger process that can expel carriers from nanotubes. The remaining carriers give rise to an induced absorption due to trion formation (binding energy 190 meV). These features show the dynamics of exciton and free carriers populations.