Dresden 2011 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 36: SC: Fe-based Superconductors - 122 - Properties, Electronic Structure, Mechanisms
TT 36.4: Talk
Wednesday, March 16, 2011, 14:45–15:00, HSZ 304
Doping dependent electronic anisotropies in Ba(Fe1−xCox)2As2 — •F. Kretzschmar1, B. Muschler1, R. Hackl1, J.-H. Chu2, 3, J. G. Analytis2,3, and I. R. Fisher2, 3 — 1Walther Meissner Institute, 85748 Garching — 2SIMES, SLAC, Menlo Park, CA 94025, USA — 3GLAM, Stanford University, CA 94305, USA
Superconductivity in the iron pnictides with Tc up to 56 K does probably not originate from electron-phonon coupling. The compounds have well nested hole and electron pockets with similar cross sections encircling the (π,0) points and the center of the (1 Fe) unit cell which can essentially be probed independently by electronic Raman scattering (ERS) in A1g and B1g symmetry, respectively. We present results of ERS experiments on Ba(Fe1−xCox)2As2 measured as a function of temperature, T>Tc, and doping x. The data of five samples with x=0.045, 0.051, 0.055, 0.061, and 0.085 with Tcmax=24 K at x=0.061 were analyzed applying an extended Drude model. The resulting dynamical relaxation rates Γµ(ω,T) are distinctly different in the two symmetries µ. In particular, the zero-energy extrapolation values Γµ(ω → 0,T) vary strongly for B1g and weakly for A1g symmetry indicating a band dependence of the electronic relaxation. Surprisingly, (ΓA1g+ΓB1g)/2 compares well with the temperature dependence of the DC resistivity. The anisotropy resembles that in cuprates. However, in the cuprates the electronic relaxation depends on the location on a single Fermi surface rather than on the individual sheet. We conclude, that in either case only the coupling of the electrons to spin and/or charge excitations can explain these anisotropies.