Water triggers high temperature superconductivity

Early last year, the world of superconductivity was turned up side down when Hideo Honoso at the Tokyo Institute of Technology in Japan announced the discovery of an entirely new type of high temperature superconductor.

The new material is a certain type of iron arsenide and confounds all known ideas about superconductivity. Iron, after all, is magnetic and so ought to destroy superconductivity, not enhance it.

Exactly how iron works its magic is still unknown but now Honoso has another surprise to throw into the mix. Today, he makes the extraordinary announcement that water vapour can trigger superconductivity in iron arsenide containing strontium at 25 K. Water, it seems, induces some kind of chemical or structural change that triggers the transition at a higher temperature. Exactly how is still puzzle. This, says the team, is an entirely new type of superconducting transition.

Interestingly, the discovery hinged on an accident that almost rivals Flemming’s discovery of antibiotics. Honoso and his team stumbled across the effect after iron arsenide samples mysteriously began to superconduct after being left out in the air for a few hours. To find the cause of the effect, the team exposed similar samples to each of the components of air, trying oxygen, nitrogen, carbon dioxide before finding that water vapour was the culprit.

The question now is whether water can do the same trick with other materials at even higher temperatures (strictly speaking high temperature superconductivity is above 30 K). Expect a flurry of papers as Honoso’s numerous rivals give the idea a run.

Ref: arxiv.org/abs/0903.3710: Water-Induced Superconductivity in SrFe2As2