Normal state charge dynamics of Fe1.06Te0.88S0.14 superconductor probed with infrared spectroscopy

TL;DR

This study uses infrared spectroscopy to analyze the normal state charge dynamics of Fe$_{1.06}$Te$_{0.88}$S$_{0.14}$, revealing incoherent metallic behavior and spectral weight redistribution, suggesting differences from other iron-based superconductor families.

Contribution

First detailed optical spectroscopy investigation of Fe$_{1.06}$Te$_{0.88}$S$_{0.14}$'s normal state, introducing generalized spectral weight analysis to understand its unique charge dynamics.

Findings

Material exhibits incoherent metallic behavior at low temperatures.

Spectral weight redistribution occurs with temperature changes.

11 family may differ from other iron-based superconductor families.

Abstract

We have used optical spectroscopy to probe the normal state electrodynamic response of Fe$_{1.06}$Te$_{0.88}$S$_{0.14}$, a member of the 11 family of iron-based superconductors with T$_c$= 8 K. Measurements have been conducted over a wide frequency range (50 - 50000 cm$^{-1}$) at selected temperatures between 10 and 300 K. At low temperatures the material behaves as an "incoherent metal": a Drude-like peak is absent from the optical conductivity, and all optical functions reveal that quasiparticles are not well defined down to the lowest measured temperature. We introduce "generalized spectral weight" analysis and use it to track temperature induced redistribution of spectral weight. Our results, combined with previous reports, indicate that the 11 family of iron-based superconductors might be different from other families.