Optical Properties of the Iron-arsenic Superconductor BaFe1.85Co0.15As2

• Published in: Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2010-11, Vol.82 (17)
• Main Authors: Tu, J.J., Homes, C., Li, J., Liu, W., Punnoose, A., Gong, Y., Ren, Y., Li, L.J., Cao, G.H., Xu, Z.A.
• Format: Article
• Language: English
• Subjects: CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ELECTRON-PHONON COUPLING; ELECTRONS; FERMI GAS; iron-arsenic superconductors; LANGMUIR FREQUENCY; OPTICAL PROPERTIES; REFLECTIVITY; SCATTERING; SUPERCONDUCTIVITY; SUPERCONDUCTORS; TRANSPORT
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.82.174509

The transport and complex optical properties of the electron-doped iron-arsenic superconductor BaFe{sub 1.85}Co{sub 0.15}As{sub 2} with T{sub c} = 25 K have been examined in the Fe-As planes above and below T{sub c}. A Bloch-Grueneisen analysis of the resistivity yields a weak electron-phonon coupling constant {lambda}{sub ph} {approx_equal} 0.2. The low-frequency optical response in the normal state appears to be dominated by the electron pocket and may be described by a weakly interacting Fermi liquid with a Drude plasma frequency of {omega}{sub p,D} {approx_equal} 7840 cm{sup -1} ({approx_equal}0.972eV) and scattering rate 1/{tau}{sub D} {approx_equal} 126 cm{sup -1} ({approx_equal}15 meV) just above T{sub c}. The frequency-dependent scattering rate 1/{tau}({Omega}) has kinks at {approx_equal}12 and 55 meV that appear to be related to bosonic excitations. Below T{sub c} the majority of the superconducting plasma frequency originates from the electron pocket and is estimated to be {omega}{sub p,S} {approx_equal} 5200 cm{sup -1} ({lambda}{sub 0} {approx_equal} 3000 {angstrom}) for T