Resonant coherent phonon generation in single-walled carbon nanotubes through near-band-edge excitation.

We have observed large-amplitude coherent phonon oscillations of radial breathing modes (RBMs) in single-walled carbon nanotubes excited through the lowest-energy (E(11)) interband transitions. In contrast to the previously studied coherent phonons excited through higher-energy (E(22)) transitions, these RBMs show comparable intensities between (n-m) mod 3 = +1 and -1 nanotubes. We also find the novel observation of RBMs excited over an excitation range of approximately 300 meV above the E(11) transition, which we attribute to possible resonance with phonon sidebands of the lowest optical transition, arising from strong exciton-phonon coupling.