title: Distinct pseudogap and quasiparticle relaxation dynamics in the superconducting state of nearly optimally doped SmFeAsO0.8F0.2 single crystals.
abstract: 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 microJ/cm{2}, respectively.
authors.affiliation: Complex Matter Department, Jozef Stefan Institute, Jamova 39, Ljubljana, SI-1000, Ljubljana, Slovenia.
authors.forename: T
authors.initials: T
authors.lastname: Mertelj
authors.forename: V V
authors.initials: VV
authors.lastname: Kabanov
authors.forename: C
authors.initials: C
authors.lastname: Gadermaier
authors.forename: N D
authors.initials: ND
authors.lastname: Zhigadlo
authors.forename: S
authors.initials: S
authors.lastname: Katrych
authors.forename: J
authors.initials: J
authors.lastname: Karpinski
authors.forename: D
authors.initials: D
authors.lastname: Mihailovic