Solution to two long-standing mysteries of cuprate superconductivity found

Scientists seeking to understand the intricacies of high-temperature superconductivity—the ability of certain materials to carry electrical current with no energy loss—have been particularly puzzled by a mysterious phase that emerges as charge carriers are added that appears to compete with superconductivity. It's also been a mystery why, within this "pseudogap" phase, the movement of superconducting electrons appears to be restricted to certain directions. So exploring the pseudogap and whether and how it affects the movement of electrons has been a pivotal challenge.

Now, a team lead by scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and Cornell University have used unique capabilities to reveal detailed characteristics of the electrons in one of these materials as it transforms from an insulator through the mysterious pseudogap phase and eventually into a full-blown superconductor. The results, described in the May 9, 2014, issue of Science, link two distinct personality changes in the material's electrons: the disappearance of a rather exotic periodic static arrangement of certain electrons within the pseudogap phase, and the sudden ability of all the material's electrons to move freely in any direction. The finding strengthens support for the idea that the periodic arrangement—variously referred to as "stripes" or "density waves"—restricts the flow of electrons and impairs maximal superconductivity in the pseudogap phase.