Effective doping and suppression of Fermi surface reconstruction via Fe vacancy disorder in KxFe2-ySe2

We investigate the effect of disordered vacancies on the normal-state electronic structure of the newly discovered alkali-intercalated iron selenide superconductors. To this end we use a recently developed Wannier function based method to calculate from first principles the configuration-averaged spectral function <A(k,w)> of K0.8Fe1.6Se2 with disordered Fe and K vacancies. We find that the disorder can suppress the expected Fermi surface reconstruction without completely destroying the Fermi surface. More interestingly, the disorder effect raises the chemical potential significantly, giving enlarged electron pockets almost identical to highly doped KFe2Se2, without adding carriers to the system.