Superconductivity and Crystal Structures of (Ba_1−<i>x</i>K_<i>x</i>)Fe₂As₂ (<i>x</i>=0–1)

Abstract

Doping improves performance: Iron arsenides (Ba1−xKx)Fe2As2 with the ThCr2Si2-type structure exhibit superconductivity at 3–38 K depending on the potassium doping level. Superconductivity occurs before the structural distortion of the parent compound BaFe2As2 (x=0) is completely suppressed by doping (see phase diagram; • critical temperature, ○ phase-transition temperature). Doping decreases the bond angles in the iron arsenide layers, suggesting a strong coupling of structural and electronic degrees of freedom.