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. (paper)