Charge-carrier dynamics in single-wall carbon nanotube bundles: a time-domain study

We present a real-time investigation of ultra-fast carrier dynamics in single-wall carbon nanotube bundles using femtosecond time-resolved photoelectron spectroscopy. The experiments allow us to study the processes governing the sub-picosecond and the picosecond dynamics of non-equilibrium charge carriers. On the sub-picosecond time scale the dynamics are dominated by ultra-fast electron-electron scattering processes, which lead to internal thermalization of the laser-excited electron gas. We find that quasiparticle lifetimes decrease strongly as a function of their energy up to 2.38 eV above the Fermi level - the highest energy studied experimentally. The subsequent cooling of the laser-heated electron gas to the lattice temperature by electron-phonon interaction occurs on the picosecond time scale and allows us to determine the electron-phonon mass enhancement parameter lambda. The latter is found to be over an order of magnitude smaller if compared, for example, with that of a good conductor such as copper.