Doping evolution of superconducting gaps and electronic densities of states in Ba(Fe1-xCox)2As2 iron pnictides

TL;DR

This study investigates how doping affects superconducting gaps and electronic states in Ba(Fe1-xCox)2As2, revealing complex interactions between magnetism, doping levels, and superconductivity through calorimetric measurements.

Contribution

It provides detailed calorimetric data on doping-dependent properties and models the superconducting gaps with a two-band isotropic s-wave approach.

Findings

Normal-state Sommerfeld coefficient varies with doping, indicating competition between magnetism and superconductivity.

Residual electronic density of states exists in all superconducting samples, minimal at optimal doping.

Superconducting gaps are well described by a two-band isotropic s-wave model.

Abstract

An extensive calorimetric study of the normal- and superconducting-state properties of Ba(Fe1-xCox)2As2 is presented for 0 < x < 0.2. The normal-state Sommerfeld coefficient increases (decreases) with Co doping for x < 0.06 (x > 0.06), which illustrates the strong competition between magnetism and superconductivity to monopolize the Fermi surface in the underdoped region and the filling of the hole bands for overdoped Ba(Fe1-xCox)2As2. All superconducting samples exhibit a residual electronic density of states of unknown origin in the zero-temperature limit, which is minimal at optimal doping but increases to the normal-state value in the strongly under- and over-doped regions. The remaining specific heat in the superconducting state is well described using a two-band model with isotropic s-wave superconducting gaps.