Strength of radial breathing mode in single-walled carbon nanotubes

We show by ab initio calculations that the electron-phonon coupling matrix element M_e-ph 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_e-ph² is up to one order of magnitude stronger for zigzag tubes than for armchair tubes. For (n₁,n₂) tubes M_e-ph depends on the value of (n₁-n₂)0.3em0exmod0.3em0ex3, which allows us to discriminate semiconducting nanotubes with similar diameter by their Raman scattering intensity. We show measured resonance Raman profiles of the radial breathing mode which support our theoretical predictions.