We report on an infrared study on the undoped compound BaFe${}_2$As${}_2$ as a function of pressure (up to about 10 GPa) at three temperatures (300, 160, and 110 K). The evolution with pressure and temperature of the optical conductivity shows that by increasing pressure, the mid-infrared absorptions associated with magnetic order are lowered while the Drude term increases, indicating the evolution towards a conventional metallic state. We evaluate the spectral weight dependence on pressure comparing it to that previously found upon doping. All the optical results indicate that lattice modifications cannot be recognized as the only parameter determining the low-energy electrodynamics in these compounds.

• Received 20 January 2012

DOI:https://doi.org/10.1103/PhysRevB.85.174522