Heat capacity jump at $T_c$ and pressure derivatives of superconducting transition temperature in the Ba ${}_{1-x}$Na ${}_x$ Fe ${}_2$As ${}_2$ ( $0.1\le x\le 0.9$ ) series

Journal Article · Thu Jan 16 00:00:00 EST 2014 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.89.014510· OSTI ID:1356982

Bud'ko, Sergey L.; Chung, Duck Young; Bugaris, Daniel; Claus, Helmut; Kanatzidis, Mercouri G.; Canfield, Paul C.

We present the evolution of the initial (up to ~ 10 kbar) hydrostatic pressure dependencies of T_c and of the ambient pressure, and the jump in the heat capacity associated with the superconducting transition as a function of Na doping in the Ba1-xNaxFe2As2 family of iron-based superconductors. For Na concentrations 0.15 ≤ x ≤ 0.9, the jump in specific heat at T_c, ΔC_p|_{T$$_c$$}, follows the ΔC_p ∝ to T³ (the so-called BNC scaling) found for most BaFe₂As₂ based superconductors. This finding suggests that, unlike the related Ba_1-xK_xFe₂As₂ series, there is no significant modification of the superconducting state (e. g., change in superconducting gap symmetry) in the Ba_1-xNa_xFe₂As₂ series over the whole studied Na concentration range. Pressure dependencies are nonmonotonic for x = 0.2 and 0.24. For other Na concentrations, T_c decreases under pressure in an almost linear fashion. The anomalous behavior of the x = 0.2 and 0.24 samples under pressure is possibly due to the crossing of the phase boundaries of the narrow antiferromagnetic tetragonal phase, unique for the Ba_1-xNa_xFe₂As₂ series, with the application of pressure. The negative sign of the pressure derivatives of T_c across the whole superconducting dome (except for x = 0.2) is a clear indication of the nonequivalence of substitution and pressure for the Ba_1-xNa_xFe₂As₂ series.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science - Office of Basic Energy Sciences - Materials Sciences and Engineering Division
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1356982
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 89, Issue 1; ISSN 1098-0121
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English