Normal state optical conductivity of Fe based superconductors

Abstract: The frequency-dependent optical response of LaFeAs iron-based superconductors, has been subject to thorough theoretical investigation. In this analysis, the optical conductivity is computed using a dual-component framework. This framework distinguishes between two types of electron behavior: one group consists of coherent Drude electrons, which play a crucial role in the superconducting properties, while the other focuses on the incoherent motion of electrons hopping between the different FeAs layers. This interplay of different electron behaviors aims to elucidate the anomalies observed in optical measurements, particularly the frequency dependence of optical conductivity in the normal state. The model primarily relies on a single adjustable parameter: the relaxation rate of these carriers. To effectively capture the frequency-dependent nature of the relaxation rates, we employ memory functions. The contributions from the coherent Drude carriers manifest as a distinct peak at zero frequency, accompanied by a gradual decline in conductivity at higher frequencies, particularly within the infrared spectrum. In contrast, the hopping mechanism, which describes the incoherent motion of electrons, produces a peak in optical conductivity that is centered in the mid-infrared region. Our analysis indicates that both the Drude electrons and the hopping carriers significantly impact the optical conduction processes LaFeAs superconductors. The findings underscore a close alignment with experimental results, revealing similar patterns of optical conductivity in both the mid-infrared and infrared frequency ranges. This comprehensive model not only accounts for the observed phenomena but also enhances our understanding of the underlying mechanisms governing the optical properties of iron based superconducting materials