Infrared pseudogap in P- and Co-doped BaFe$_{2}$As$_{2}$ superconductors

We investigated the in-plane electronic response of P- and Co-doped BaFe$_{2}$As$_{2}$ compounds using infrared spectroscopy. We found hallmarks of the normal-state pseudogap in the optical spectra of the BaFe$_{2}$As$_{2}$ system, which are very similar with those of the cuprates. Based on the evolution of the electronic response with doping and across the superconducting transition, we suggest that the antiferromagnetic fluctuations can be a possible origin of the infrared pseudogap in the iron pnictides. We will also discuss implications of our results for the origin of the pseudogap in the cuprates.