Spectroscopic signatures of many-particle energy levels in non-covalently doped single-wall carbon nanotubes

TL;DR

This study reveals optical signatures of many-particle energy levels in non-covalently doped single-wall carbon nanotubes, demonstrating exciton-to-trion conversion and the formation of polaron-dressed excitons through spectroscopy.

Contribution

First observation of an excited trion state in doped nanotubes and evidence for polaron-dressed excitons and their energy levels.

Findings

Detection of excited trion state T* at 2.12 eV

Confirmation of exciton-to-trion conversion via photoluminescence

Evidence for polaron-dressed exciton formation

Abstract

We report the first observation of an optical transition from a ground trion state T to excited trion state T* in (6,5) single-wall carbon nanotubes non-covalently doped with hydrochloric acid. The position of such an excited trion level T* is estimated as 2,12 eV, while the ground trion level T has an energy of 1,08 eV. Besides, pump-probe transient absorption spectroscopy indicates that the ground trion level T cannot be excited directly. Instead, we propose that trions form after nonradioactive relaxation from excitons, dressed by interaction with doping induced hole-polarons. We also report a complete exciton-to-trion conversion by means of photoluminescence spectroscopy, thus supporting existence of the polaron-dressed exciton energy level in p-doped single-wall carbon nanotubes.