title: Ultrafast dynamics of quasiparticles and coherent acoustic phonons in slightly underdoped (BaK)Fe2As2.
abstract: We have utilized ultrafast optical spectroscopy to study carrier dynamics in slightly underdoped (BaK)Fe2As2 crystals without magnetic transition. The photoelastic signals due to coherent acoustic phonons have been quantitatively investigated. According to our temperature-dependent results, we found that the relaxation component of superconducting quasiparticles persisted from the superconducting state up to at least 70 K in the normal state. Our findings suggest that the pseudogaplike feature in the normal state is possibly the precursor of superconductivity. We also highlight that the pseudogap feature of K-doped BaFe2As2 is different from that of other iron-based superconductors, including Co-doped or P-doped BaFe2As2.
authors.affiliation: Institute of Physics, Academia Sinica, Taipei 11529, Taiwan.|Institute of Photonics Technologies, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Kung-Hsuan
authors.initials: KH
authors.lastname: Lin
authors.affiliation: Institute of Physics, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Kuan-Jen
authors.initials: KJ
authors.lastname: Wang
authors.affiliation: Institute of Physics, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Chung-Chieh
authors.initials: CC
authors.lastname: Chang
authors.affiliation: Institute of Physics, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Yu-Chieh
authors.initials: YC
authors.lastname: Wen
authors.affiliation: Texas Center for Superconductivity, University of Houston, Houston, TX 77004, USA.|Department of Physics, The University of Texas at Dallas, Richardson, TX 75080, USA.
authors.forename: Bing
authors.initials: B
authors.lastname: Lv
authors.affiliation: Texas Center for Superconductivity, University of Houston, Houston, TX 77004, USA.
authors.forename: Ching-Wu
authors.initials: CW
authors.lastname: Chu
authors.affiliation: Institute of Physics, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Maw-Kuen
authors.initials: MK
authors.lastname: Wu