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arXiv · 1007.3151

Disorder effects in pnictides : a tunneling spectroscopy study

Y. Noat·T. Cren·V. Dubost·S. Lange·F. Debontridder·J. Marcus·P. Toulemonde·W. Sacks·D. Roditchev
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Abstract

We present the synthesis and the tunneling spectroscopy study of superconducting FeSe0.5Te0.5 (Tc = 14 K), SmFeAsO0.85 (Tc = 45 K) and SmFeAsO0.9F0.1 (Tc = 52 K). The samples were characterized by Rietveld refinement of X-ray diffraction patterns and transport measurements. Tunneling experiments on FeSe0.5Te0.5 revealed a single superconducting gap of ~1 meV in BCS-like tunnelling conductance spectra. In SmFeAsO0.85 and SmFeAsO0.9F0.1 however, more complex spectra were observed characterized by two gap-like structures at ~4 meV and ~10 meV. These spectra are qualitatively understood assuming a two-band superconductor with a 's\pm' order parameter. We show that depending on the sign relation between the pairing amplitudes in the two bands, the interband quasiparticle scattering has a crucial effect on the shape of the tunneling spectra. Detailed analysis of the tunneling spectroscopy data supports the 's\pm' model, but single-gap spectra found in FeSe0.5Te0.5 are more compatible with a disorder-induced 's'-wave gap, due to the Se-Te substitution.

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Y. Noat, T. Cren, V. Dubost, S. Lange, F. Debontridder, J. Marcus, P. Toulemonde, W. Sacks, D. Roditchev. 2010-07-21. Disorder effects in pnictides : a tunneling spectroscopy study. https://doi.org/10.1088/0953-8984%2F22%2F46%2F465701

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