Effect of Fermi Surface Nesting on Resonant Spin Excitations in   Ba1-xKxFe2As2
  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. 
J.-P. Castellan, S. Rosenkranz, E. A. Goremychkin, D. Y. Chung, I. S.   Todorov, M. G. Kanatzidis, I. Eremin, J. Knolle, A. ...
cond-mat.supr-con cond-mat.str-el