title: Optical spectroscopy of superconducting Ba0.55K0.45Fe2As2: evidence for strong coupling to low-energy bosons.
abstract: Normal state optical spectroscopy on single crystals of the new iron arsenide superconductor Ba0.55K0.45Fe2As2 shows that the infrared spectrum consists of two major components: a strong metallic Drude band and a well-separated midinfrared absorption centered at 0.7 eV. It is difficult to separate the two components unambiguously but several fits using Lorentzian peaks suggest a model with a Drude peak having a plasma frequency of 1.6 to 2.1 eV and a midinfrared peak with a plasma frequency of 2.5 eV. Detailed analysis of the frequency dependent scattering rate shows that the charge carriers interact with a broad bosonic spectrum extending beyond 100 meV with a very large coupling constant lambda=3.4 at low temperature. As the temperature increases this coupling weakens to lambda=0.78 at ambient temperature. This suggests a bosonic spectrum that is similar to what is seen in the lower Tc cuprates.
authors.affiliation: Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Yang
authors.forename: D
authors.initials: D
authors.lastname: Hüvonen
authors.forename: U
authors.initials: U
authors.lastname: Nagel
authors.forename: T
authors.initials: T
authors.lastname: Rõõm
authors.forename: N
authors.initials: N
authors.lastname: Ni
authors.forename: P C
authors.initials: PC
authors.lastname: Canfield
authors.forename: S L
authors.initials: SL
authors.lastname: Bud'ko
authors.forename: J P
authors.initials: JP
authors.lastname: Carbotte
authors.forename: T
authors.initials: T
authors.lastname: Timusk