Photoinduced Quasiparticle Relaxation Dynamics in Near-optimally Doped SmFeAsO0.8F0.2 Single Crystals

We investigate the quasiparticle relaxation and low-energy electronic structure in a near-optimally doped pnictide superconductor with T c =49.5 K by means of femtosecond spectroscopy. Multiple relaxation processes are evident, with distinct superconducting state dynamics and a clear “pseudogap”-like feature with an onset above 180 K indicating the existence of a temperature-independent gap of magnitude Δ PG =61±9 meV above and below T c . The fluence and temperature dependence of the superconducting state dynamics shows similar behaviour to the cuprate superconductors with the superconducting-condensate vaporization energy of E va / k B ≈1.5 K per Fe ion.