Specific heat of Ca${}_{0.32}$Na${}_{0.68}$Fe${}_2$As${}_2$ single crystals: unconventional s${}_{\pm }$ multi-band superconductivity with intermediate repulsive interband coupling and sizable attractive intraband couplings

Abstract

We report a low-temperature specific heat study of high-quality single crystals of the heavily hole doped superconductor Ca${}_{0.32}$Na${}_{0.68}$Fe${}_2$As${}_2$. This compound exhibits bulk superconductivity with a transition temperature $T_c\approx 34$\,K, which is evident from the magnetization, transport, and specific heat measurements. The zero field data manifests a significant electronic specific heat in the normal state with a Sommerfeld coefficient $\gamma \approx 53$ mJ/mol K${}^2$. Using a multi-band Eliashberg analysis, we demonstrate that the dependence of the zero field specific heat in the superconducting state is well described by a three-band model with an unconventional s${}_{\pm }$ pairing symmetry and gap magnitudes ${\Delta }_i$ of approximately 2.35, 7.48, and -7.50 meV. Our analysis indicates a non-negligible attractive intraband coupling,which contributes significantly to the relatively high value of $T_c$. The Fermi surface averaged repulsive and attractive coupling strengths are of comparable size and outside the strong coupling limit frequently adopted for describing high-$T_c$ iron pnictide superconductors. We further infer a total mass renormalization of the order of five, including the effects of correlations and electron-boson interactions.

8 Figures, Submitted to PRB

References in corpus (19)

• High-temperature superconductivity in iron-based materials
• Is LaO${}_{1-x}$F${}_x$FeAs an electron-phonon superconductor ?
• Pressure induced superconductivity in CaFe${}_2$As${}_2$
• First order structural phase transition in CaFe${}_2$As${}_2$
• Synthesis and Properties of CaFe${}_2$As${}_2$ Single Crystals
• A Systematic Study of Electron-Phonon Coupling to Oxygen Modes Across the Cuprates
• Fully Gapped Superconducting State Based on a High Normal State Quasiparticle Density of States in Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ Single Crystals
• Low temperature specific heat of the hole-doped Ba_{0.6}K_{0.4}Fe_2As_2 single crystals and electron-doped SmFeAsO_{0.9}F_{0.1} samples
• Upper critical field, anisotropy, and superconducting properties of Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ single crystals
• Electron-phonon interaction in the t-J model
• Anisotropic three-dimensional magnetism in CaFe2As2
• Time of life as it is in LiFeAs
• Emergence of superconductivity at 45 K by lanthanum and phosphorus co-doping of CaFe2As2
• Thermodynamic properties of Ba1-xMxFe2As2 (M = La and K)
• Electronic band structure and momentum dependence of the superconducting gap in (Ca, Na)Fe2As2 from angle-resolved photoemission spectroscopy
• Magnetic penetration-depth measurements of a suppressed superfluid density of superconducting Ca${}_{0.5}$Na${}_{0.5}$Fe${}_2$As${}_2$ single crystals by proton irradiation
• Point-contact spectroscopy in Co-doped CaFe2As2: nodal superconductivity and topological Fermi surface transition
• Conventional Superconductivity in Fe-Based Pnictides: the Relevance of Intra-Band Electron-Boson Scattering
• Spin density wave and superconductivity in CaFe_{1-x}Co_{x}AsF studied by nuclear magnetic resonance

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