Abstract
We investigate the electronic properties and the superconducting gap characteristics of a single crystal of hole-doped 122 Fe-pnictide BaNaFeAs by means of specific-heat measurements. The specific heat exhibits a pronounced anomaly around the superconducting transition temperature 29.4 K and a small residual part at low temperature. In a magnetic field of 90 kOe, the transition is broadened and is lowered insignificantly by an amount 1.5 K. We estimate a high electronic coefficient in the normal state with a value 57.5 mJ mol K, being consistent with hole-doped 122 compounds. The temperature-dependent superconducting electronic specific heat cannot be described with single-gap BCS theory under the weak-coupling approach. Instead, our analysis implies a presence of two -wave-like gaps with magnitudes 1.06 and 2.08 with respective weights of and 52%. While our results have qualitative similarities with other hole-doped 122 materials, the gap's magnitude and their ratio are quite different.
- Received 28 March 2011
DOI:https://doi.org/10.1103/PhysRevB.84.064525
©2011 American Physical Society