Electronic scattering effects in europium-based iron pnictides

Abstract In a comprehensive study, we investigate the electronic scattering effects in EuFe 2 ( As 1 − x P x ) 2 by using Fourier-transform infrared spectroscopy. In spite of the fact that Eu 2 + local moments order at around T Eu ∼ 20 K , the overall optical response is strikingly similar to the one of the well-known Ba-122 pnictides. The main difference lies within the suppression of the lower spin-density-wave gap feature. By analyzing our spectra with a multi-component model, we find that the high-energy feature around 0.7 eV – often associated with Hund's rule coupling – is highly sensitive to the spin-density-wave ordering; this further confirms its direct relationship to the dynamics of itinerant carriers. The same model is also used to investigate the in-plane anisotropy of magnetically detwinned EuFe 2 As 2 in the antiferromagnetically ordered state, yielding a higher Drude weight and lower scattering rate along the crystallographic a-axis. Finally, we analyze the development of the room-temperature spectra with isovalent phosphor substitution and highlight changes in the scattering rate of hole-like carriers induced by a Lifshitz transition.