The strength of the radial-breathing mode in single-walled carbon nanotubes

TL;DR

This study uses ab initio calculations and experimental data to reveal that the electron-phonon coupling strength of the radial breathing mode in single-walled carbon nanotubes varies significantly with chirality, affecting Raman scattering intensities.

Contribution

It demonstrates the dependence of electron-phonon coupling on nanotube chirality and provides a method to distinguish semiconducting nanotubes by their Raman signals.

Findings

Coupling strength varies with tube chirality, up to tenfold difference.

Raman intensity can discriminate nanotubes with similar diameters.

Experimental Raman profiles support theoretical predictions.

Abstract

We show by ab initio calculations that the electron-phonon coupling matrix element M of the radial breathing mode in single-walled carbon nanotubes depends strongly on tube chirality. For nanotubes of the same diameter the coupling strength |M|^2 is up to one order of magnitude stronger for zig-zag than for armchair tubes. For (n,m) tubes M depends on the value of (n-m) mod 3, which allows to discriminate semiconducting nano tubes with similar diameter by their Raman scattering intensity. We show measured resonance Raman profiles of the radial breathing mode which support our theoretical predictions.