Neutron-Inelastic-Scattering Peak by Dissipationless Mechanism in the s++ -wave State in Iron-based Superconductors

TL;DR

This paper demonstrates that the broad neutron scattering peak in iron-based superconductors can be explained by a dissipationless quasiparticle mechanism in the s++-wave state, aligning well with experimental observations.

Contribution

The study introduces a dissipationless quasiparticle mechanism to explain neutron scattering peaks in s++-wave superconductors, improving agreement with experimental data.

Findings

Hump-shaped enhancement appears above 2Delta in s++ state

Resonance peak height and weight are larger in s+- state than experiments

Dissipationless mechanism explains broad spectral peaks in experiments

Abstract

We investigate the neutron scattering spectrum in iron pnictides based on the random-phase approximation in the five-orbital model with a realistic superconducting (SC) gap, Delta=5meV. In the normal state, the neutron spectrum is suppressed by large inelastic quasi-particle (QP) scattering rate gamma* ~ Delta. In the fully-gapped s-wave state without sign reversal (s++), a hump-shaped enhancement appears in the neutron spectrum just above 2Delta, since the inelastic QP scattering is prohibited by the SC gap. That is, the hump structure is produced by the dissipationless QPs for Ek<3Delta. The obtained result is more consistent with experimental spectra, compared to the results of our previous paper with Delta=50meV. On the other hand, both height and weight of the resonance peak in the fully-gapped s-wave states with sign reversal (s+-) are much larger than those observed in experiments. We conclude that experimentally observed broad spectral peak in iron pnictides is created by the present "dissipationless mechanism" in the s++ -wave state.