Exciton binding energies in carbon nanotubes from two-photon photoluminescence

TL;DR

This study uses one- and two-photon photoluminescence spectroscopy to measure exciton binding energies in single-walled carbon nanotubes, revealing strong Coulomb interactions and stable excitons at room temperature.

Contribution

It provides direct experimental evidence of excitonic states and binding energies in carbon nanotubes, supported by ab-initio calculations, advancing understanding of their electronic and optical properties.

Findings

Exciton binding energies of 0.3-0.4 eV were measured.

Distinct excitonic states were identified via spectroscopy.

Results show strong Coulomb correlations in nanotubes.

Abstract

One- and two-photon luminescence excitation spectroscopy showed a series of distinct excitonic states in single-walled carbon nanotubes. The energy splitting between one- and two-photon-active exciton states of different wavefunction symmetry is the fingerprint of excitonic interactions in carbon nanotubes. We determine exciton binding energies of 0.3-0.4 eV for different nanotubes with diameters between 0.7 and 0.9 nm. Our results, which are supported by ab-initio calculations of the linear and non-linear optical spectra, prove that the elementary optical excitations of carbon nanotubes are strongly Coulomb-correlated, quasi-one dimensionally confined electron-hole pairs, stable even at room temperature. This alters our microscopic understanding of both the electronic structure and the Coulomb interactions in carbon nanotubes, and has direct impact on the optical and transport properties of novel nanotube devices.