Observation of multiple superconducting gaps in the infrared reflectivity spectra of $\mathrm{Ba(Fe_{0.9}Co_{0.1})_2As_2}$

The results of infrared reflectivity measurements for the iron-based high-temperature superconductor $\mathrm{Ba(Fe_{0.9}Co_{0.1})_2As_2}$ are reported. The reflectivity is found to be close to unity at frequencies $\omega $ lower than $2\Delta /h$ ($2\Delta $ is the superconducting gap and $h$ is Planck's constant). This is evidence for the $s^{+/-}$ or $s^{+/+}$ symmetry of the superconducting order parameter in the studied compound. The infrared reflectivity spectra of $\mathrm{Ba(Fe_{0.9}Co_{0.1})_2As_2}$ manifest opening of several superconducting gaps at temperatures lower than critical $T_{c}$.