Spectroscopic and thermodynamic properties in a four-band model for pnictides

Abstract

In this paper we provide a comprehesive analysis of different properties of pnictides both in the normal and superconducting state, with a particular focus on the optimally-doped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ system. We show that, by using the band dispersions experimentally measured by ARPES, a four-band Eliashberg model in the intermediate-coupling regime can account for both the measured hierarchy of the gaps and for several spectroscopic and thermodynamic signatures of low-energy renormalization. These include the kinks in the band dispersion and the effective masses determined via specific-heat and superfluid-density measurements. We also show that, although an intermediate-coupling Eliashberg approach is needed to account for the magnitude of the gaps, the temperature behavior of the thermodynamic quantities does not show in this regime a significant deviation with respect to weak-coupling BCS calculations. This can explain the apparent success of two-band BCS fits of experimental data reported often in the literature.

12 pages, 6 figures, final version

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• Eliashberg Analysis of Optical Spectra Reveals Strong Coupling of Charge Carriers to Spin Fluctuations in Superconducting Iron Pnictides
• Evidence for Unconventional Superconductivity and Nontrivial Topology in PdTe
• Contribution of Collective Excitations to Third Harmonic Generation in Multiband Superconductors: the case of MgB${}_2$
• Infrared probe of the gap evolution across the phase diagram of Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Gap Anisotropy in Iron-Based Superconductors: A Point-Contact Andreev Reflection Study of BaFe${}_{2-x}$Ni${}_x$As${}_2$ Single Crystals
• Superconductivity by Hidden Spin Fluctuations in Electron-Doped Iron Selenide
• Constraints on the total coupling strength to bosons in iron based superconductors
• A phenomenological multiband Eliashberg model for LiFeAs
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