Specific heat measurements of Ba0.68 K0.32 Fe2 As2 single crystals: evidence for a multiband strong-coupling superconducting state

P. Popovich, A.V. Boris, O.V. Dolgov, Alexandre Avraamovitch Golubov, S.L. Sun, C.T. Lin, R.K. Kremer, B. Keimer

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Abstract

The specific heat of high-purity Ba0.68 K0.32 Fe2 As2 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, 2Δmax/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.
Original languageEnglish
Article number027003
Pages (from-to)-
JournalPhysical review letters
Volume105
Issue number2
DOIs
Publication statusPublished - 2010

Keywords

  • METIS-270361
  • IR-97891

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