Gap Structure of the Overdoped Iron-Pnictide Superconductor Ba(Fe${}_{0.942}$Ni${}_{0.058}$)${}_2$As${}_2$: A Low-Temperature Specific-Heat Study

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.

5 pages, 4 figures

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