Time- and momentum-resolved phonon-induced relaxation dynamics in carbon nanotubes.

Applying the density matrix formalism, we obtain microscopic access to the time- and momentum-resolved carrier relaxation dynamics driven by acoustic and optical phonons in semiconducting carbon nanotubes. Our calculations predict two clearly distinguishable relaxation times: the ultrafast component in the femtosecond range is ascribed to the scattering with optical phonons, while the slower component on a time scale of a few picoseconds stems from acoustic phonons. Investigating a number of different nanotubes sheds light on the diameter and chirality dependence of the phonon-induced carrier relaxation dynamics. The difference in the carrier-phonon coupling elements and in the dispersion relation for optical and acoustic phonons explains the significant variation in the efficiency of the corresponding relaxation channels.