Determination of the pairing state in iron-based superconductors through neutron scattering

TL;DR

This paper investigates the pairing symmetry in iron-based superconductors by calculating spin susceptibility for different states, suggesting experimental tests to distinguish between s_{+-} and s_{++} pairing.

Contribution

It provides a detailed theoretical analysis of spin susceptibility in different pairing states considering quasiparticle damping, guiding experimental identification of pairing symmetry.

Findings

s_{+-} state aligns with experiments at typical damping levels

s_{++} state becomes plausible with larger damping and gaps

Proposes experimental investigation at wave vector (pi,pi) for distinction

Abstract

We calculate the spin susceptibility in the s_{+-} and s_{++} superconducting states of the iron pnictides using the effective five orbital model and considering the quasiparticle damping. For the experimentally evaluated magnitude of the quasiparticle damping and the superconducting gap, the results at the wave vector ~ (pi,0) show that the s_{+-} state is more consistent with the neutron scattering experiments, while for larger quasiparticle damping and the superconducting gap, the s_{++} state can be more consistent. To distinguish between two cases that reproduce the experiments at the wave vector ~ (pi,0), we propose to investigate experimentally the wave vector ~ (pi,pi).