Regular Article THE EUROPEAN PHYSICAL JOURNAL B

Abstract. We report on a thorough optical investigation of BaFe2As2 over a broad spectral range and as a function of temperature, focusing our attention on its spin-density-wave (SDW) phase transition at TSDW = 135 K. While BaFe2As2 remains metallic at all temperatures, we observe a depletion in the far infrared energy interval of the optical conductivity below TSDW, ascribed to the formation of a pseudogap-like feature in the excitation spectrum. This is accompanied by the narrowing of the Drude term consistent with the dc transport results and suggestive of suppression of scattering channels in the SDW state. About 20 % of the spectral weight in the far infrared energy interval is affected by the SDW phase transition. PACS. 75.30.Fv Spin-density waves – 78.20.-e Optical properties of bulk materials and thin films A new field in condensed matter research was recently ini-tiated by the discovery of superconductivity in doped iron oxyarsenides [1]. After the first report on LaFeAs(O1−xFx) with a critical temperature Tc of 26 K, even higher tran-sition temperatures up to 55 K were reached in fluorine doped SmFeAs(O1−xFx) [1,2]. This novel family of com-pounds has generated a lot of interest, primarily becaus