Dispersive Spin Fluctuations in the near optimally-doped superconductor Ba(Fe1-xCox)2As2 ($x$=0.065)

TL;DR

This study uses inelastic neutron scattering to investigate spin excitations in a near-optimally doped superconductor, revealing persistent anisotropic dispersive modes and enhanced susceptibility compared to its antiferromagnetic parent.

Contribution

It provides new insights into the spin excitation spectrum of Ba(Fe1-xCox)2As2 in the superconducting state, highlighting anisotropic dispersions and their connection to the spin resonance.

Findings

Anisotropic spin-wave velocity persists in the superconducting state.

Dispersive spin excitations connect to the spin resonance.

Enhanced local susceptibility compared to parent compound.

Abstract

Inelastic neutron scattering is used to probe the collective spin excitations of the near optimally-doped superconductor Ba(Fe1-xCox)2As2 ($x$=0.065). Previous measurements on the antiferromagnetically ordered parents of this material show a strongly anisotropic spin-wave velocity. Here we measure the magnetic excitations up to 80 meV and show that a similar anisotropy persists for superconducting compositions. The dispersive mode measured here connects directly with the spin resonance previously observed in this compound. When placed on an absolute scale, our measurements show that the local- or wavevector- integrated susceptibility is larger in magnitude than that of the ordered parents over the energy range probed.