Nonequilibrium superconductivity in Y1-xPrxBa2Cu3O7 thin films

We have measured the picosecond conductivity dynamics in Y1-xPrxBa2Cu3O7 thin films from 0.3-2.0 terahertz. Our experimental technique measures the complex conductivity $\sigma_{re}(\omega$) + i$\sigma_{im}(\omega$) permitting the simultaneous observation of superconducting pair and quasiparticle dynamics. We emphasize aspects of the conductivity dynamics which extend our previous results. In particular, the recovery of $\sigma_{re}$ is faster than $\sigma_{im}$, and the recovery of $\sigma_{im}$ decreases with increasing frequency. This suggests another carrier relaxation pathway, in addition to superconducting pair recovery, following optical excitation.