Gap structure in the electron-doped Iron-Arsenide Superconductor Ba(Fe0.92Co0.08)2As2: low-temperature specific heat study

TL;DR

This study investigates the low-temperature specific heat of the electron-doped Ba(Fe0.92Co0.08)2As2 superconductor, revealing complex gap structures that suggest anisotropic or nodal superconducting gaps.

Contribution

It provides detailed specific heat measurements under magnetic fields, indicating the necessity of an anisotropic gap model for this superconductor, advancing understanding of its pairing symmetry.

Findings

Presence of low-energy excitations in the superconductor

Single s- or d-wave models cannot explain the data

Data suggest an anisotropic gap possibly with nodes

Abstract

We report the field and temperature dependence of the low-temperature specific heat down to 400 mK and in magnetic fields up to 9 T of the electron-doped Ba(Fe0.92Co0.08)2As2 superconductor. Using the phonon specific heat obtained from pure BaFe2As2 we find the normal state Sommerfeld coefficient to be 18 mJ/mol.K^2 and a condensation energy of 1.27 J/mol. The temperature dependence of the electronic specific heat clearly indicate the presence of the low-energy excitations in the system. The magnetic field variation of field-induced specific heat cannot be described by single clean s- or d-wave models. Rather, the data require an anisotropic gap scenario which may or may not have nodes. We discuss the implications of these results.