Specific Heat Discontinuity DeltaC vs Tc in Annealed Ba(Fe1-xCox)2As2

Abstract

The low temperature specific heat of annealed single crystal samples of Ba(Fe1-xCox)2As2 with compositions spanning the entire superconducting phase diagram was measured. Effort was made to discover the best annealing schedule to maximize Tc and minimize transition width in these samples. Values of deltaC/Tc normalized to 100% superconducting volume fractions varied proportionally to Tc^alpha. Within a rather narrow error bar of +-0.15, the exponent alpha was the same (approximately 2) over a range of compositions (0.055 < x < 0.15) around the optimal concentration, x=0.08, where Tc is the maximum in the phase diagram. Thus, whether the superconductivity was coexistent with magnetism (underdoped) or not (overdoped) did not affect the non-BCS variation (alpha nearly 2 instead of 0.8-0.9 for BCS superconductors) of deltaC/Tc with Tc. The annealed samples in the present work, with increased deltaC/Tc and Tc values compared to previous results for the Ba(Fe1-xCox)2As2 alloy system, suggest that the intrinsic value of the exponent alpha for the iron superconductors, when the samples are annealed, with fewer defects, may indeed be even further from the BCS value of 0.8-0.9 than previously thought.

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• Evolution of London penetration depth with scattering in single crystals of K${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$
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• Universal scaling behavior of the upper critical field in strained FeSe0.7Te0.3 thin films
• Universal Scaling Law for the Condensation Energy, U, Across a Broad Range of Superconductor Classes
• The change of electronic state and crystal structure by post-annealing in superconducting SrFe2(As0.65P0.35)2
• Rutgers relation for the analysis of superfluid density in superconductors
• Unusual Sensitivity of Superconductivity to Strain in Iron-Based 122 Superconductors
• Structural phases of elemental Gallium: universal relations in type-I superconductors
• Specific Heat Investigation for Line Nodes in Heavily Overdoped Ba1-xKxFe2As2
• Specific Heat vs Field of LiFe1-xCuxAs
• The Origin of Condensation Energy Scaling of the Fe-based superconductors
• Superconductivity In K- And Na- Doped Bafe2as2: What Can We Learn From Heat Capacity And Pressure Dependence of Tc
• Calculation of the specific heat of optimally K-doped BaFe${}_2$As${}_2$