Spin excitations in hole-overdoped iron-based superconductors

TL;DR

This study investigates the spin excitations in hole-overdoped Ba1-xKxFe2As2 superconductors using inelastic neutron scattering, revealing how magnetic interactions correlate with superconductivity suppression in overdoped regimes.

Contribution

It provides a comprehensive analysis of spin fluctuations across the entire Brillouin zone in overdoped iron-based superconductors, highlighting the relationship between magnetic exchange and superconductivity.

Findings

Spin spectra include spin wave and chimney-like dispersions.

Chimney-like dispersion indicates itinerant magnetism.

Spin wave bandwidth decreases significantly in overdoped region.

Abstract

Understanding the overall features of magnetic excitation is essential for clarifying the mechanism of Cooper pair formation in iron-based superconductors. In particular, clarifying the relationship between magnetism and superconductivity is a central challenge because magnetism may play a key role in their exotic superconductivity. BaFe2As2 is one of ideal systems for such investigation because its superconductivity can be induced in several ways, allowing a comparative examination. Here we report a study on the spin fluctuations of the hole-overdoped iron-based superconductors Ba1-xKxFe2As2 (x = 0.5 and 1.0; Tc = 36 K and 3.4 K, respectively) over the entire Brillouin zone using inelastic neutron scattering. We find that their spin spectra consist of spin wave and chimney-like dispersions. The chimney-like dispersion can be attributed to the itinerant character of magnetism. The band width of the spin wave-like dispersion is almost constant from the non-doped to optimum-doped region, which is followed by a large reduction in the overdoped region. This suggests that the superconductivity is suppressed by the reduction of magnetic exchange couplings, indicating a strong relationship between magnetism and superconductivity in iron-based superconductors.