Electronic decay rates in semiconducting carbon nanotubes

Temperature can induce some free carriers in semiconducting carbon nanotubes (SCNs). Such carriers would exhibit the temperature-dependent electronic excitations. The dielectric function ε, which represents the intrinsic excitation properties, is calculated with the random-phase approximation (RPA). The screened excitation spectra include both L=0 intraband e–h excitations and L=1 damped interband plasmon. Such electronic excitations are very effectively deexcitation channels. When electrons are excited from valence bands to conduction bands by the external fields, they could further decay by the e–e Coulomb interactions. Time-resolved carrier deexcitations processes in SCNs have been investigated by means of pump-probe experiments. This is the first theoretical work on the electron decay rate due to the e–e Coulomb interactions. The Fermi Golden rule, which includes the screened e–e interactions, is used to calculate the decay rate. 1/τ is very sensitive to change in state energy or wave vector. The L=0 intraband e–h deexcitations mainly occur in the low-energy states, and the band-edge state has the largest decay rate. The high-energy state might be deexcited by the L=1 mode. The calculated results could essentially explain the experimental measurements from the time-resolved photoemission spectroscopy.