Specific Heat Discontinuity, deltaC, at Tc in BaFe2(As0.7P0.3)2 - Consistent with Unconventional Superconductivity

Abstract

We report the specific heat discontinuity, deltaC/Tc, at Tc = 28.2 K of a collage of single crystals of BaFe2(As0.7P0.3)2 and compare the measured value of 38.5 mJ/molK**2 with other iron pnictide and iron chalcogenide (FePn/Ch) superconductors. This value agrees well with the trend established by Bud'ko, Ni and Canfield who found that deltaC/Tc ~ a*Tc**2 for 14 examples of doped Ba1-xKxFe2As2 and BaFe2-xTMxAs2, where the transition metal TM=Co and Ni. We extend their analysis to include all the FePn/Ch superconductors for which deltaC/Tc is currently known and find deltaC/Tc ~ a*Tc**1.9 and a=0.083 mJ/molK**4. A comparison with the elemental superconductors with Tc>1 K and with A-15 superconductors shows that, contrary to the FePn/Ch superconductors, electron-phonon-coupled conventional superconductors exhibit a significantly different dependence of deltaC on Tc, namely deltaC/Tc ~ Tc**0.9. However deltaC/gamma*Tc appears to be comparable in all three classes (FePn/Ch, elemental and A-15) of superconductors with, e. g., deltaC/gamma*Tc=2.4 for BaFe2(As0.7P0.3)2. A discussion of the possible implications of these phenomenological comparisons for the unconventional superconductivity believed to exist in the FePn/Ch is given.

arXiv commentsome disagreement in reference and footnote numbering with the published version

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• Superconducting specific heat jump $\Delta C_{\mathrm{el}}\propto T_c^{\beta }(\beta \approx 2)$ for K${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$
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• Strong-Coupling Superconductivity in NaFe${}_{1-x}$Co${}_x$As: the Eliashberg Theory and Beyond
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• Heat capacity jump at T_c and pressure derivatives of superconducting transition temperature in the Ba(1-x)NaxFe2As2 (0.1 <= x <= 0.9) series
• Coexistence of superconductivity and magnetism in CaK(Fe${}_{1-x}$Ni${}_x$)${}_4$As${}_4$ as probed by ${}^{57}$Fe Mössbauer spectroscopy
• Specific heat jump at superconducting transition in the presence of Spin-Density-Wave in iron-pnictides
• Power Law Like Correlation between Condensation Energy and Superconducting Transition Temperatures in Iron Pnictide/Chalcogenide Superconductors: Beyond the BCS Understanding
• Effect of SDW fluctuations on the specific heat jump in iron pnictides at a superconducting transition
• Universal Scaling Law for the Condensation Energy, U, Across a Broad Range of Superconductor Classes
• Structural phases of elemental Gallium: universal relations in type-I superconductors
• Superconducting gap in BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$ from temperature dependent transient optical reflectivity
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