Evidence for multiple superconducting gaps in optimally doped BaFe1.87Co0.13As2 from infrared spectroscopy

We performed combined infrared reflection and ellipsometry measurements of the in-plane optical response of single crystals of the pnictide high-temperature superconductor BaFe1.87Co0.13As2 with T-c=24.5 K. Our experimental data provide evidence for multiple superconducting energy gaps and can be well described in terms of three isotropic gaps with 2 Delta/k(B)T(c) of 3.1, 4.7, and 9.2. The obtained low-temperature value of the in-plane magnetic penetration depth is 270 nm.