Coupled multiple-mode theory for $s_{\pm}$ pairing mechanism in iron based superconductors

TL;DR

This paper develops a coupled mode theory to analyze the interaction between magnetic and superconducting states in iron-based superconductors, revealing how fluctuations influence phase transitions near the tetracritical point.

Contribution

It introduces a dynamical mode-mode coupling framework and a Ginzburg-Landau functional to study the interplay of SDW and SC fluctuations in multi-band superconductors.

Findings

Fluctuation corrections suppress magnetic transition.

Intraband and interband fluctuations nearly cancel in the superconducting channel.

The theory provides insights into phase diagram behavior near the tetracritical point.

Abstract

We investigate the interplay between the magnetic and the superconducting degrees of freedom in unconventional multi-band superconductors such as iron pnictides. For this purpose a dynamical mode-mode coupling theory is developed based on the coupled Bethe-Salpeter equations. In order to investigate the region of the phase diagram not too far from the tetracritical point where the magnetic spin density wave, (SDW) and superconducting (SC) transition temperatures coincide, we also construct a Ginzburg - Landau functional including both SC and SDW fluctuations in a critical region above the transition temperatures. The fluctuation corrections tend to suppress the magnetic transition, but in the superconducting channel the intraband and interband contribution of the fluctuations nearly compensate each other.