2010/08/31 by J. J. Tu, Jiajing Tu, Jackie Li +13 · 1 citation
Chemistry · Materials Science · Physics and Astronomy · #Chemistry #Condensed matter physics #Coupling (piping) #Crystallography #Fermi liquid theory #Iron-based superconductors research #Materials science #Omega #Physics #Quantum mechanics #Rare-earth and actinide compounds #Scattering #Superconductivity #Superconductivity in MgB2 and Alloys #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.82.174509
published as Phys. Rev. B 82, 174509 (2010) [10 pages] · Revised version (expanded discussion, additional references): 11 pages, one table and 8 figures
arxiv created 2010/10/25 · openalex publication_date 2010/11/12 · arxiv updated 2010/11/16 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The transport and complex optical properties of the electron-doped iron-arsenic superconductor BaFe1.85Co0.15As2 with Tc=25 K have been examined in the Fe-As planes above and below Tc. A Bloch-Gr"uneisen analysis of the resistivity yields a weak electron-phonon coupling constant \ensuremathλph\ensuremath≃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 \ensuremathωp,D\ensuremath≃7840 cm^\ensuremath-1 (\ensuremath≃0.972eV) and scattering rate 1/\ensuremathτD\ensuremath≃126 cm^\ensuremath-1 (\ensuremath≃15 meV) just above Tc. The frequency-dependent scattering rate 1/\ensuremathτ(\ensuremathω) has kinks at \ensuremath≃12 and 55 meV that appear to be related to bosonic excitations. Below Tc the majority of the superconducting plasma frequency originates from the electron pocket and is estimated to be \ensuremathωp,S\ensuremath≃5200 cm^\ensuremath-1 (\ensuremathλ0\ensuremath≃3000 \text\AA) for T⪡Tc, indicating that less than half the free carriers in the normal state have collapsed into the condensate, suggesting that this material is not in the clean limit. Supporting this finding is the observation that this material falls close to the universal scaling line for a Bardeen, Cooper, and Schrieffer dirty-limit superconductor in the weak-coupling limit. There are two energy scales for the superconductivity in the optical conductivity and photoinduced reflectivity at \ensuremathΔ1(0)\ensuremath≃3.1\ifmmode±\else\textpm\fi0.2 meV and \ensuremathΔ2(0)\ensuremath≃7.4\ifmmode±\else\textpm\fi0.3 meV. This corresponds to either the gapping of the electron and hole pockets, respectively, or an anisotropic s-wave gap on the electron pocket; both views are consistent with the s^\ifmmode±\else\textpm\fi model.