Magnetic resonance from the interplay of frustration and superconductivity

TL;DR

This paper develops a theoretical model for magnetic excitations in iron-based superconductors, revealing a magnetic resonance near a specific wavevector due to the coexistence of antiferromagnetic order and superconductivity.

Contribution

It introduces a self-consistent electronic theory capturing the interplay of frustration and superconductivity in magnetic excitations of iron-based superconductors.

Findings

Superconductivity induces a magnetic resonance near wavevector Q2.

Resonance is isotropic in spin space, contrasting with excitations near Q1.

The theory predicts observable features in experiments.

Abstract

Motivated by the iron-based superconductors, we develop a self-consistent electronic theory for the itinerant spin excitations in the regime of coexistence of the antiferromagnetic stripe order with wavevector ${\bf Q}_{1} = (\pi,0)$ and $s^{+-}$ superconductivity. The onset of superconductivity leads to the appearance of a {\em magnetic} resonance near the wavevector ${\bf Q}_{2} = (0,\pi)$ where magnetic order is absent. This resonance is isotropic in spin space, unlike the excitations near ${\bf Q}_{1}$ where the magnetic Goldstone mode resides. We discuss several features which can be observed experimentally.