Chirality dependence of electron-phonon matrix elements in semiconducting single-walled carbon nanotubes

Evaluations of quantum coupling between electrons and phonons in well-defined nanostructure will be necessary when applications based on the vibrations of various materials move into the quantum regime. Raman scattering, in which changes in polarization within a material are probed by light, is an excellent means of analyzing electron-phonon coupling. In this study, the Raman intensities of individually suspended single-walled carbon nanotubes were determined in order to examine variations in electron-phonon interactions in response to changes in the arrangement of carbon atoms (i.e., chirality). Unambiguous assignment of nanotube chirality was achieved by photoluminescence spectroscopy and similar variations in the radial breathing mode and intermediate frequency mode peak intensities with changes in chirality were found. These phenomena were explained based on prior theoretical studies. The D-mode and G-mode peaks were also observed to respond in the same manner, based on which we assigned the longitudinal optical phonon branch to the D-mode. The results of this work demonstrate that the Raman intensity analysis can provide useful information regarding electron-phonon coupling in nanomaterials.