Electronic Scattering Effects in Europium-Based Iron Pnictides

S. Zapf; D. Neubauer; K. W. Post; A. Kadau; J. Merz; C. Clauss; A. Löhle; H. S. Jeevan; P. Gegenwart; D. N. Basov; M. Dressel

doi:10.1016/j.crhy.2015.04.008

paper

Electronic Scattering Effects in Europium-Based Iron Pnictides

arXiv:1602.06544 · doi:10.1016/j.crhy.2015.04.008

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 around $T_{Eu} \approx 20$ \,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 analysing 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 analyse 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.