Effect of Fermi Surface Nesting on Resonant Spin Excitations in Ba1-xKxFe2As2

TL;DR

This study investigates how Fermi surface nesting influences resonant spin excitations in Ba1-xKxFe2As2, revealing that reduced nesting weakens magnetic resonance and correlates with decreased superconducting transition temperature.

Contribution

It provides experimental and theoretical evidence linking Fermi surface mismatch to changes in magnetic resonance and superconductivity in iron-based superconductors.

Findings

Superconducting transition temperature decreases with hole doping.

Resonant spin excitations split into two incommensurate peaks with doping.

Fermi surface nesting reduction correlates with resonance collapse.

Abstract

We report inelastic neutron scattering measurements of the resonant spin excitations in Ba1-xKxFe2As2 over a broad range of electron band filling. The fall in the superconducting transi- tion temperature with hole doping coincides with the magnetic excitations splitting into two incom- mensurate peaks because of the growing mismatch in the hole and electron Fermi surface volumes, as confirmed by a tight-binding model with s+- symmetry pairing. The reduction in Fermi surface nesting is accompanied by a collapse of the resonance binding energy and its spectral weight caused by the weakening of electron-electron correlations.