Nonequilibrium Superconductivity and Quasiparticle Dynamics Studied by Photoinduced Activation of mm-Wave Absorption

We present a study of nonequilibrium superconductivity in ${\mathrm{DyBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ using photoinduced activation of mm-wave absorption. We monitor the time evolution of the thin film transmissivity at $5{\mathrm{cm}}^{-1\mathrm{}}$ subject to pulsed infrared radiation. In addition to a positive bolometric signal we observe a second, faster, decay with a sign opposite to the bolometric signal for $T>\mathrm{}40\mathrm{K}$. We attribute this to the unusual properties of quasiparticles residing near the nodes of an unconventional superconductor, resulting in a strong enhancement of the recombination time.