Terahertz conductivity spectroscopy of Co-doped BaFe$_2$As$_2$ Thin Film

TL;DR

This study uses terahertz spectroscopy to analyze the complex conductivity of Co-doped BaFe$_2$As$_2$ thin films, revealing superconducting properties and low-energy excitations without Kramers-Kronig transformation.

Contribution

It provides detailed terahertz spectral data on Fe-based superconductors, including superconducting gap and penetration depth, using a direct electromagnetic measurement method.

Findings

Normal state shows Drude-type conductivity.

Superconducting state exhibits typical superconducting frequency dependence.

Superconducting gap estimated at 2.8 meV.

Abstract

We investigated the complex conductivity spectrum of a Co-doped BaFe$_2$As$_2$ epitaxial thin film in the THz region. In the normal state, the complex conductivity shows a Drude-type frequency dependence, while in the superconducting state, the frequency dependence of the complex conductivity changes to that of a typical superconducting materials. We estimated the magnetic penetration depth at absolute zero to be 710 nm and the superconducting gap energy to be 2.8 meV, which is considered to be the superconducting gap opened at the electron-type Fermi surface near the M point. We succeeded in obtaining the low-energy elementary excitation of a Fe-based superconductor using the electromagnetic method without invoking the Kramers-Kronig transformation.