Femtosecond spectroscopy studies of ultrafast dynamics in PrxY1-xBa2Cu3O7 and YBa2Cu3O7-delta thin films at different temperatures

Abstract

We have systematically measured the transient reflectivity (Delta R/R) in Pr-doped YBCO (PrxY1-xBa2Cu3O7) and partially oxygen deficient YBCO (YBa2Cu3O7-delta) thin films at temperatures ranging from 300 K to 12 K by using the femtosecond pump-probe technique. At room temperature, the electron-phonon coupling strength and the position of Fermi-level as a function of Pr doping concentration and oxygen content have been studied. Measurements performed at low temperatures indicate that the magnitude, polarity, and relaxation time of the transient reflectivity is strongly dependent on the photon energy and pumping intensity of the optical excitation, the ambient temperature, and the doping level of the superconducting thin films. Moreover, the temperature dependence of the Fermi-level position was also observed.