Distinct Pseudogap and Quasiparticle Relaxation Dynamics in the Superconducting State of Nearly Optimally Doped SmFeAsO0.8F0.2 Single Crystals

We use femtosecond spectroscopy to investigate the quasiparticle relaxation and low-energy electronic structure in a nearly optimally doped pnictide superconductor with T-c=49.5 K. Multiple relaxation processes are evident, with distinct superconducting state quasiparticle recombination dynamics exhibiting a T-dependent superconducting gap, and a clear pseudogaplike feature with an onset above 180 K indicating the existence of a temperature-independent gap of magnitude Delta(PG)=61 +/- 9 meV above T-c. Both the superconducting and pseudogap components show saturation as a function of fluence with distinct saturation fluences 4 and 40 mu J/cm(2), respectively.