Conventional Superconductivity in Fe-Based Pnictides: the Relevance of Intra-Band Electron-Boson Scattering

TL;DR

The paper argues that conventional phonon-mediated pairing explains superconductivity in Fe-based pnictides, emphasizing the importance of intra-band electron-boson scattering and the role of isotope effects, challenging the notion of unconventional pairing mechanisms.

Contribution

It highlights the significance of intra-band electron-boson interactions and isotope effects in Fe-based superconductors, supporting a conventional phonon-mediated pairing model.

Findings

Large Fe-isotope effect supports phonon-mediated pairing.

Intra-band impurity scattering is crucial for understanding pairing.

Inter-band scattering may suppress but not eliminate s(+-) pairing.

Abstract

Various recent experimental data and especially the large Fe-isotope effect point against unconventional pairings, since the large intra-band impurity scattering is strongly pair-breaking for them. The strength of the inter-band impurity scattering in some single crystals may be strong and probably beyond the Born scattering limit. In that case the proposed s(+-) pairing (hole(h)- and electron(el)-gaps are of opposite signs) is suppressed but possibly not completely destroyed. The data imply that the intra-band pairing in the h- and in the el-band, which are inevitably due to some nonmagnetic el-boson interaction (EBI), must be taken into account. EBI is either due to phonons (EPI) or possibly due to excitons (EEI), or both are simultaneously operative. We discuss their interplay briefly. The large Fe-isotope effect favors the EPI and the s(+) pairing (the h- and el-gaps are in-phase).