The underlying theory is simple enough. "If you can get electrons to pair, they can superconduct," said Dean. According to the Bardeen-Cooper-Schrieffer (BCS) theory, an attractive force between electrons—no matter how weak—will cause those electrons to pair up and form a new kind of particle called a "Cooper pair." These behave like particles called bosons and, at low enough temperatures, can enter into a collective state and move through a material unimpeded by disorder—a feature any single electron just cannot achieve on its own. But there's been a problem. "Electrons do not want to pair," said Dean. Like repels like,...