title: Band-dependent quasiparticle dynamics in single crystals of the Ba(0.6)K(0.4)Fe2As2 superconductor revealed by pump-probe spectroscopy.
abstract: We report on band-dependent quasiparticle dynamics in Ba(0.6)K(0.4)Fe2As2 (Tc=37 K) measured using ultrafast pump-probe spectroscopy. In the superconducting state, we observe two distinct relaxation processes: a fast component whose decay rate increases linearly with excitation density and a slow component with an excitation density independent decay rate. We argue that these two components reflect the recombination of quasiparticles in the two hole bands through intraband and interband processes. We also find that the thermal recombination rate of quasiparticles increases quadratically with temperature. The temperature and excitation density dependence of the decays indicates fully gapped hole bands and nodal or very anisotropic electron bands.
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Darius H
authors.initials: DH
authors.lastname: Torchinsky
authors.forename: G F
authors.initials: GF
authors.lastname: Chen
authors.forename: J L
authors.initials: JL
authors.lastname: Luo
authors.forename: N L
authors.initials: NL
authors.lastname: Wang
authors.forename: Nuh
authors.initials: N
authors.lastname: Gedik