Neutron scattering study of the oxypnictide superconductor La(O,F)FeAs

TL;DR

This neutron scattering study of La(O,F)FeAs reveals no spin-density-wave order and suggests that superconductivity may not be driven by electron-phonon coupling, providing insights into the pairing mechanism.

Contribution

The paper provides the first neutron scattering analysis of La(O,F)FeAs, showing the absence of SDW order and constraining the magnetic resonance peak, advancing understanding of its superconducting mechanism.

Findings

No SDW order observed in normal or superconducting states.

Upper limit set for magnetic resonance peak consistent with extended s-wave pairing.

Phonon spectrum energy scale supports electron-phonon coupling but does not explain high Tc.

Abstract

The newly discovered superconductor La(O,F)FeAs (Tc = 26 K) was investigated using the neutron scattering technique. No spin-density-wave (SDW) order was observed in the normal state nor in the superconducting state, both with and without an applied magnetic field of 9 T, consistent with the proposal that SDW and superconductivity are competing in the laminar materials. While our inelastic measurements offer no constraints on the spin dynamic response from d-wave pairing, an upper limit for the magnetic resonance peak predicted from an extended s-wave pairing mechanism is provided. Our measurements also support the energy scale of the calculated phonon spectrum which is used in electron-phonon coupling theory, and fails to produce the high observed Tc.