Ultrafast dynamics of superconducting K3C60 and Rb3C60

We report the results of a detailed experimental and theoretical study of the ultrafast relaxation processes in superconducting K3C60, and Rb3C60 films. Room temperature pump-probe spectra were obtained for different pump and probe wavelengths. Low-temperature measurements through the phase transition temperature T-c. were performed to monitor the quasiparticle dynamics in the superconducting state. For comparison we performed measurements on YBa2Cu3O7 under similar conditions. An intuitive model is presented to explain the temperature and wavelength dependence of our experimental results for both the superconducting and normal phases.