Magnetic and superconducting instabilities in a hybrid model of itinerant/localized electrons for iron pnictides

TL;DR

This paper presents a minimal model for iron pnictides that unifies the mechanisms behind spin-density-wave order and superconductivity, showing how their interplay is driven by coupling between itinerant electrons and local moments, with results aligning qualitatively with experiments.

Contribution

It introduces a unified minimal model capturing SDW and superconductivity in iron pnictides, highlighting the role of critical coupling between itinerant electrons and local moments.

Findings

Phase diagram matches experimental observations.

Spin susceptibility shows Goldstone and resonance modes.

Strong electron-moment scattering persists above Tc.

Abstract

We study a unified mechanism for spin-density-wave (SDW) and superconductivity in a minimal model, in which itinerant electrons and local moments coexist as previously proposed for the iron pnictides [EPL, 88, 17010 (2009)]. The phase diagram obtained at the mean field level is in qualitative agreement with the experiment, which shows how the magnetic and superconducting (SC) instabilities are driven by the critial coupling between the itinerant/localized electrons. The spin and charge response functions at the random phase approximation (RPA) level further characterize the dynamical evolution of the system. In particular, the dynamic spin susceptibility displays a Goldstone mode in the SDW phase, which evolves into a gapped resonance-like mode in the superconducting phase. The latter persists all the way into the normal state above Tc, where a strong scattering between the itinerant electrons and local moments is restored, as an essential feature of the model.