Coexistence of static magnetism and superconductivity in SmFeAsO1-xFx as revealed by muon spin rotation

TL;DR

This study reveals that static magnetism coexists with superconductivity in SmFeAsO1-xFx, suggesting magnetic fluctuations play a crucial role in high-temperature superconductivity in pnictides, similar to cuprates.

Contribution

The paper provides muon spin rotation evidence of coexistence of static magnetism and superconductivity in SmFeAsO1-xFx, highlighting the role of magnetic fluctuations in high-Tc superconductors.

Findings

Static magnetism persists into the superconducting regime.

Magnetic ground states differ between pnictides and cuprates.

Magnetic fluctuations may be key to high-Tc superconductivity.

Abstract

The recent observation of superconductivity with critical temperatures up to 55 K in the FeAs based pnictide compounds marks the first discovery of a non copper-oxide based layered high-Tc superconductor (HTSC) [1-3]. It has raised the suspicion that these new materials share a similar pairing mechanism to the cuprates, since both exhibit superconductivity following charge doping of a magnetic parent material. Here we present a muon spin rotation study on SmFeAsO1-xFx (x=0-0.30), which shows that static magnetism persists well into the superconducting regime. The analogy with the cuprates is quite surprising since the parent compounds appear to have different magnetic ground states: itinerant spin density wave for the pnictides contrasted with the Mott-Hubbard insulator in the cuprates. Our findings suggest that proximity to magnetic order and associated soft magnetic fluctuations, rather than the strong electronic correlations in the vicinity of a Mott-Hubbard-metal-to-insulator transition, may be the key ingredients of HTSC.