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arXiv · 0912.0140

Evidence for multiple superconducting gaps in optimally doped BaFe$_{1.87}$Co$_{0.13}$As$_{2}$ from infrared spectroscopy

K. W. Kim·M. Rössle·A. Dubroka·V. K. Malik·T. Wolf·C. Bernhard
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Abstract

We performed combined infrared reflection and ellipsometry measurements of the in-plane optical reponse of single crystals of the pnictide high temperature superconductor BaFe$_{1.87}$Co$_{0.13}$As$_{2}$ with $T_{c}$ = 24.5 K. We observed characteristic superconductivity-induced changes which provide evidence for at least three different energy gaps. We show that a BCS-model of isotropic gaps with 2$\Delta/k_{B}T_{c}$ of 3.1, 4.7, and 9.2 reproduces the experimental data rather well. We also determine the low-temperature value of the in-plane magnetic penetration depth of 270 nm.

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K. W. Kim, M. Rössle, A. Dubroka, V. K. Malik, T. Wolf, C. Bernhard. 2009-12-01. Evidence for multiple superconducting gaps in optimally doped BaFe$_{1.87}$Co$_{0.13}$As$_{2}$ from infrared spectroscopy. https://doi.org/10.1103/physrevb.81.214508

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