Specific heat measurements of Ba(0.68)K(0.32)Fe2As2 single crystals: evidence for a multiband strong-coupling superconducting state

The specific heat of high-purity Ba(0.68)K(0.32)Fe2As2 single crystals with the highest reported superconducting Tc=38.5 K was studied. The electronic specific heat Cp below Tc shows two gap features, with Δ1≈11 meV and Δ2≈3.5 meV obtained from an α-model analysis. The reduced gap value, 2Δ(max)/kBT...

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Bibliographic Details
Published in:Physical review letters 2010-07, Vol.105 (2), p.027003-027003
Main Authors: Popovich, P, Boris, A V, Dolgov, O V, Golubov, A A, Sun, D L, Lin, C T, Kremer, R K, Keimer, B
Format: Article
Language:English
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Summary:The specific heat of high-purity Ba(0.68)K(0.32)Fe2As2 single crystals with the highest reported superconducting Tc=38.5 K was studied. The electronic specific heat Cp below Tc shows two gap features, with Δ1≈11 meV and Δ2≈3.5 meV obtained from an α-model analysis. The reduced gap value, 2Δ(max)/kBTc≈6.6, the magnitude of the specific-heat jump, ΔCp(Tc)/Tc, and its slope below Tc exhibit a strong-coupling character. We also show that an Eliashberg model with two hole and two electron bands gives the correct values of Tc, the superconducting gaps, and the free-energy difference.
ISSN:1079-7114