Looking at the superconducting gap of iron pnictides

TL;DR

This paper reviews optical spectroscopy studies of iron pnictide superconductors, focusing on their superconducting gaps, low-lying excitations, and the ongoing debate about their interpretation.

Contribution

It provides a comprehensive overview of optical investigations on 122 and 11 family iron pnictides, highlighting current understanding and debates.

Findings

Optical spectroscopy reveals details of superconducting gaps.

Experimental data are consistent across groups but interpretations vary.

Studies shed light on low-lying excitations and electron-phonon interactions.

Abstract

THz and infrared spectroscopy is widely utilized to investigate the electrodynamic properties of the novel iron-based superconductors in the normal and superconducting states. Besides electronic excitations and correlations, electron-phonon coupling and the influence of magnetism, the experiments yield important information on low-lying excitations and help to clarify the number and symmetry of superconducting gaps. While the experimental data of different groups converge, the interpretation is still under debate. Here we review the status of optical investigations on the superconducting state for the 122 and 11 family of iron pnictides.