Strong spin resonance on BaFe2(As0.65P0.35)2 with Tc = 30 K

TL;DR

This study uses inelastic neutron scattering to observe a strong spin resonance in the P-doped iron-based superconductor BaFe2(As0.65P0.35)2 with Tc=30K, suggesting sign reversal of the order parameter despite line nodes.

Contribution

It provides experimental evidence of spin resonance in a superconductor with line nodes, indicating sign reversal persists and offering insights into the pairing symmetry.

Findings

Spin resonance observed at 12 meV in the superconducting state.

Resonance enhancement comparable to other iron-based superconductors.

Horizontal line nodes are a plausible explanation for the observations.

Abstract

We performed inelastic neutron scattering on powder sample of the P-doped iron-based superconductor BaFe2(As0.65P0.35)2 with Tc = 30K, whose superconducting (SC) order parameter is expected to have line nodes. We have observed spin resonance at Q $\sim$ 1.2{\AA}^{-1} and E=12 meV in the SC state. The resonance enhancement, which can be a measure of the area of sign reversal between the hole and electron Fermi surfaces (FSs), is comparable to those of other iron-based superconductors without line nodes. This fact indicates that the sign reversal between the FSs is still dominant in this system, and the line nodes should create only limited area of sign-reversal on a single FS. Hence the system can hold relatively high-Tc. Comparison with theoretical calculation indicates horizontal line nodes may be a candidate to reproduce the observation.