Prediction of superconductivity in compounds based on iridium oxide opens a new chapter for superconductors: "A number of groups have tried to make iridium oxide superconductors," says Yunoki. "So far, they have been able to make the compound metallic, but they have not yet succeeded in making it superconducting."
To probe the possible reasons for the elusiveness of superconductivity in iridium oxides, Yunoki's team developed a theoretical model to describe the compound's properties. They were able to calculate that superconductivity could be achieved by introducing atoms of other elements to provide a surplus of electrons—a process known as electron doping. "This is exactly where our theoretical work becomes valuable," says Yunoki. "We have provided a guideline by showing that, as opposed to copper oxides, the superconductivity in Sr2IrO4 appears most likely with an electron surplus, not with a deficit."