Low temperature specific heat in BaFe1.9Ni0.1As2 single crystals

TL;DR

This study measures the low-temperature specific heat of BaFe1.9Ni0.1As2 single crystals, revealing a specific heat jump at Tc and insights into the superconducting gap structure through magnetic field dependence analysis.

Contribution

It provides detailed low-temperature specific heat data and interprets the superconducting gap structure in BaFe1.9Ni0.1As2 using magnetic field dependence.

Findings

Observed a specific heat jump at Tc of approximately 23 mJ/mol K^2.

Found a linear magnetic field dependence of the electronic specific heat coefficient at low temperatures.

Indicated a fully gapped Fermi pocket with possible complex gap structure at other Fermi surfaces.

Abstract

Low-temperature specific heat was measured on the BaFe1.9Ni0.1As2 single crystals with critical transi-tion temperature Tc = 20.1 K. A clear specific heat jump with the value \DeltaC/T|Tc \approx 23 mJ/mol K^2 has been observed. In addition, a roughly linear magnetic field dependence of the electronic specific heat coefficient \Delta\gamma(H) is found in the zero-temperature limit, suggesting that at least one Fermi pocket, probably the hole derivative one, is fully gapped with a small anisotropy in the present sample. A slight curvature of the curve \Delta\gamma(H) may suggest a complex gap structure (anisotropic gap or nodes) at other Fermi surfaces.