Infrared spectrum and its implications for the electronic structure of the semiconducting iron selenide K$_{0.83}$Fe$_{1.53}$Se$_2$

TL;DR

This study uses infrared spectroscopy to explore the electronic structure of K$_{0.83}$Fe$_{1.53}$Se$_2$, revealing unique spectral features linked to Fe vacancy ordering and magnetic interactions, differing from other Fe-based superconductors.

Contribution

It provides new insights into the electronic and magnetic structure of semiconducting iron selenide through infrared spectral analysis and interpretation of Fe vacancy effects.

Findings

Distinct infrared spectral features compared to other Fe-based systems

Presence of a double peak structure indicating magnetic coexistence

Abundant phonon modes due to Fe vacancy ordering

Abstract

We report an infrared spectroscopy study on K$_{0.83}$Fe$_{1.53}$Se$_2$, a semiconducting parent compound of the new iron-selenide system. The major spectral features are found to be distinctly different from all other Fe-based superconducting systems. Our measurement revealed two peculiar spectral structures: a double peak structure between 4000-6000 cm$^{-1}$ and abundant phonon modes much more than those expected for a 122 structure. We elaborate that those features could be naturally explained from the blocked antiferromagnetism due to the presence of Fe vacancy ordering as determined by recent neutron diffraction experiments. The double peaks reflect the coexistence of ferromagnetic and antiferromagnetic couplings between the neighboring Fe sites.