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TT: Fachverband Tiefe Temperaturen

TT 8: Superconductivity: Fe-based Superconductors - 122 Part 1

TT 8.7: Vortrag

Montag, 26. März 2012, 16:30–16:45, H 2053

A light scattering study of the superconducting gap in Ba_0.6K_0.4Fe₂As₂ — •Florian Kretzschmar¹, Bernhard Muschler¹, Rudi Hackl¹, Tom Devereaux^2,3, and Hai-Hu Wen⁴ — ¹Walther Meissner Institut, Bayerische Akademie der Wissenschaften, 85748 Garching — ²Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA — ³Geballe Laboratory for Advanced Materials & Dept. of Applied Physics, Stanford University, CA 94305, USA — ⁴Nanjing University, Nanjing, P.R. China

We present results of electronic Raman scattering experiments on optimally doped Ba_0.6K_0.4Fe₂As₂ in the superconducting state. In contrast to Ba(Fe_1−xCo_x)₂As₂ we find superconductivity features in all symmetries. The observed gaps depend strongly on the band index but are only weakly momentum-dependent on the individual bands. We find a small gap 2Δ in the range 10 meV on one hole-like band and two large and rather isotropic gaps of 23 meV on the other hole-like band and 25 meV on the electron-like bands, respectively. Below a symmetry independent threshold of approximately 25 cm⁻¹ the Raman response is very small and nearly energy independent. Although the intensity is not exactly zero it is safe to conclude that there is a full gap on all bands having a magnitude of at least 1 k_BT_c. This work is supported by the DFG via the SPP 1458.