Anisotropy of incommensurate magnetic excitations in slightly overdoped Ba$_{0.5}$K$_{0.5}$Fe$_2$As$_2$ probed by polarized inelastic neutron scattering experiments

TL;DR

This study uses polarized inelastic neutron scattering to investigate magnetic excitations in a slightly overdoped iron-based superconductor, revealing anisotropic and dispersive magnetic resonance behavior despite heavy doping.

Contribution

It provides new insights into the anisotropic magnetic excitations in overdoped Ba$_{0.5}$K$_{0.5}$Fe$_2$As$_2$ using polarized neutron scattering, highlighting the persistence of magnetic anisotropy.

Findings

Magnetic resonance peaks at ~15 meV in the superconductor.

Magnetic correlations are anisotropic below the resonance energy.

Correlations become isotropic at the resonance maximum.

Abstract

Polarized neutron scattering experiments on the slightly overdoped superconductor Ba$_{0.5}$K$_{0.5}$Fe$_2$As$_2$ reveal broad magnetic resonance scattering peaking at approximately 15 meV. In spite of doping far beyond the suppression of magnetic order, this compound exhibits dispersive and anisotropic magnetic excitations. At energies below the resonance maximum, magnetic correlations polarized parallel to the layers but perpendicular to the propagation vector are reduced by a factor two compared to those in the two orthogonal directions; in contrast correlations at the peak maximum are isotropic.