Gap Structure of the Overdoped Iron-Pnictide Superconductor Ba(Fe$_{0.942}$Ni$_{0.058}$)$_{2}$As$_{2}$: A Low-Temperature Specific-Heat Study

TL;DR

This study investigates the low-temperature specific heat of an overdoped Ba(Fe,Ni)2As2 superconductor, revealing evidence of line nodes in its energy gap, which enhances understanding of its superconducting gap structure.

Contribution

It provides experimental evidence of line nodes in the energy gap of overdoped Ba(Fe,Ni)2As2, supporting theoretical predictions and previous findings in similar systems.

Findings

Observation of a T^2 term in specific heat indicating line nodes

Critical temperature determined to be 14.8 K

Results consistent with theoretical models of nodal superconductors

Abstract

Low-temperature specific heat (SH) is measured on the postannealed Ba(Fe_{1-x}Ni_x)_2As_2 single crystal with x = 0.058 under different magnetic fields. The sample locates on the overdoped sides and the critical transition temperature is determined to be 14.8 K by both the magnetization and SH measurements. A simple and reliable analysis shows that, besides the phonon and normal electronic contributions, a clear T2 termemerges in the low temperature SH data.Our observation is similar to that observed in the Co-doped system in our previous work and is consistent with the theoretical prediction for a superconductor with line nodes in the energy gap.