Revealing two-competing processes in carrier dynamics of single-walled carbon nanotube films

Ultrafast time-resolved optical transmission in single-walled carbon nanotubes was measured as a function of pump fluence at a temperature of 200 K employing degenerate pump-probe experiment. We observed a relaxation dynamics with two components characterized by 0.1 and 1 ps, respectively. The signal amplitude of the slow component also shows a crossover from negative to positive when the pump fluence decreased. It is suggested that the fast component is related to the intraband relaxation and the slow component is attributed to two-competing processes.