Robust Nodal Superconductivity Induced by Isovalent Doping inBa(Fe1−xRux)2As2andBaFe2(As1−xPx)2

Superconductivity arises from pairing of mobile electrons. The symmetry of the electron-pair wave function contains important clues about the mechanism underlying the pairing. A Chinese-Korean experimental collaboration carries out element-selective substitutional doping of BaFe${}_{2}$As${}_{2}$ and searches for the pairing symmetry of the resulting iron-based superconductors.