Coherent Phonons in Carbon Nanotubes and Graphene

We develop a theory for generation and detection of coherent phonons in graphene and carbon nanotubes. Coherent phonons are generated via phonon interactions with photogenerated carriers. Electronic states are treated in an extended tight binding model while phonon modes are treated using valence force field models. The amplitude for each coherent phonon mode satisfies a driven oscillator equation with a driving function that depends on the photoexcited carrier distributions.