Two-band BCS superconductivity in Ba(Fe0.9Co0.1)2As2

TL;DR

This study investigates the optical spectra of Ba(Fe0.9Co0.1)2As2, revealing two distinct superconducting gaps and confirming a two-band BCS model with detailed electronic parameters, consistent with photoemission data.

Contribution

It provides the first detailed optical spectral analysis of Ba(Fe0.9Co0.1)2As2, demonstrating two-band superconductivity with specific energy gaps and electronic parameters.

Findings

Identification of two superconducting gaps at 3.7 meV and ≥7 meV.

Determination of plasma frequencies and scattering rates for electron and hole bands.

Consistency with electronic photoemission experiments.

Abstract

The conductivity and permittivity optical spectra of iron-pnictide Ba(Fe0.9Co0.1)2As2 film (Tc=20 K) are analyzed. In the superconducting state, at all temperatures up to Tc the temperature dependences of the magnetic field penetration depth and of the superconducting condensate density are well described within the generalized two-band BCS model with intraband and interband pairing interactions considered. It is shown that the smaller superconducting energy gap 2{\Delta} = 3.7 meV develops in the electronic subsystem while the larger gap 2{\Delta} >= 7 meV opens in the hole subsystem. The normal state parameters (plasma frequencies and scattering rates) of electron and hole conduction bands are determined. At all temperatures the obtained data are consistent with the results of electronic photoemission experiments on Ba(Fe1-x Cox)2As2.