Strong coupling to magnetic fluctuations in the charge dynamics of Fe-based superconductors

TL;DR

This study compares the infrared charge response of two Fe-based superconductors with magnetic order, revealing how different magnetic patterns influence charge dynamics and proposing an optical absorption mechanism.

Contribution

It provides a detailed comparison of charge dynamics in two Fe-based compounds, linking magnetic ordering patterns to optical response differences and proposing a new absorption mechanism.

Findings

Magnetic ordering affects plasma frequency and scattering.

Distinct mid-infrared features correlate with magnetic patterns.

Proposed optical absorption mechanism consistent with multiple experiments.

Abstract

We present a comprehensive comparison of the infrared charge response of two systems, characteristic of classes of the 122 pnictide (SrFe2As2) and 11 chalcogenide (Fe_1.087Te) Fe compounds with magnetically-ordered ground states. In the 122 system, the magnetic phase shows a decreased plasma frequency and scattering, and associated appearance of strong mid-infrared features. The 11 system, with a different magnetic ordering pattern, also shows decreased scattering, but an increase in the plasma frequency, while no clear mid-infrared features appear below the ordering temperature. We suggest how this marked contrast can be understood in terms of the diverse magnetic ordering patterns of the ground state, and conclude that while the high temperature phases of these systems are similar, the magnetic ordering strongly affects the charge dynamical response. In addition, we propose an optical absorption mechanism which appears to be consistent with information gained from several different experiments.