Phase diagram and Gap anisotropy in Iron-Pnictide Superconductors

TL;DR

This study employs the FLEX approximation on a five-band Hubbard model to explore superconductivity in iron-pnictides, revealing doping-dependent behaviors, the significance of pnictogen height, and the link between pairing interactions and magnetic phases.

Contribution

It introduces a static potential to prevent Fermi surface deformation and analyzes the pairing symmetry and interactions across doping levels in iron-pnictide superconductors.

Findings

Superconductivity persists more in hole doping than electron doping.

Distinct superconducting gap symmetries are observed between hole and electron doped systems.

The pairing interaction is closely related to proximity to antiferromagnetic phases.

Abstract

Using the fluctuation-exchange (FLEX) approximation we study an effective five-band Hubbard model for iron-pnictide superconductors obtained from the first-principles band structure. We preclude deformations of the Fermi surface due to electronic correlations by introducing a static potential, which mimics the effect of charge relaxation. Evaluating the Eliashberg equation for various dopings and interaction parameters, we find that superconductivity can sustain higher hole than electron doping. Analyzing the symmetry of the superconducting order parameter we observe clear differences between the hole and electron doped systems. We discuss the importance of the pnictogen height for superconductivity. Finally, we dissect the pairing interaction into various contributions, which allows us to clarify the relationship between the superconducting transition temperature and the proximity to the anti-ferromagnetic phase.