Emergent magnetic degeneracy in iron pnictides due to the interplay between spin-orbit coupling and quantum fluctuations

TL;DR

This paper demonstrates that spin-orbit coupling and quantum fluctuations in iron pnictides lead to emergent magnetic degeneracy near the quantum critical point, which may be linked to high-temperature superconductivity.

Contribution

It introduces a renormalization group analysis showing how spin-orbit coupling causes magnetic degeneracy in iron pnictides near criticality, impacting superconductivity.

Findings

Magnetic states become nearly degenerate near the quantum critical point.

Spin-orbit coupling stabilizes a Gaussian fixed point with a large basin of attraction.

Magnetic degeneracy correlates with the highest superconducting transition temperature.

Abstract

Recent experiments in iron pnictide superconductors reveal that, as the putative magnetic quantum critical point is approached, different types of magnetic order coexist over a narrow region of the phase diagram. Although these magnetic configurations share the same wave-vectors, they break distinct symmetries of the lattice. Importantly, the highest superconducting transition temperature takes place close to this proliferation of near-degenerate magnetic states. In this paper, we employ a renormalization group calculation to show that such a behavior naturally arises due to the effects of spin-orbit coupling on the quantum magnetic fluctuations. Formally, the enhanced magnetic degeneracy near the quantum critical point is manifested as a stable Gaussian fixed point with a large basin of attraction. Implications of our findings to the superconductivity of the iron pnictides are also discussed.