High-energy spin excitations in heavily hole-doped superconductor KFe$_{2}$As$_{2}$

The understanding of overall spin dynamics over the wide hole doping region is a key to progress in the study of iron based superconductors. In contrast to experimental works in parent compounds, spin dynamics in over hole doping region is not yet provided. In this research, we have performed inelastic neutron scattering of heavily hole-doped KFe$_{2}$As$_{2}$ at 4SEASONS. We revealed a well-defined low-energy incommensurate spin fluctuation at (0.32, 0.32) and (0.68, 0.68). This incommensurability was consistent with the previous triple-axis neutron scattering study. A practically vertical dispersion was discovered up to 80meV and spin fluctuations clearly exist even in heavily hole doped KFe$_{2}$As$_{2}$. The energy dependence of dynamical magnetic susceptibility $\chi $(q,w) can be explained by a phenomenological function applicable to correlated spin system in Fermi liquid without magnetic long-range ordering. Therefore, magnetism in KFe$_{2}$As$_{2}$ likely originates from itinerant nature.