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

摘要

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