Measurements taken at the National Institute of Standards and Technology (NIST) may help physicists develop a clearer understanding of high-temperature superconductors, whose behavior remains in many ways mysterious decades after their discovery. A new copper-based compound exhibits properties never before seen in a superconductor and could be a step toward solving part of the mystery.
Copper-based high-temperature superconductors are created by taking a nonconducting material called a Mott insulator and either adding or removing some electrons from its crystal structure. As the quantity of electrons is raised or lowered, the material undergoes a gradual transformation to one that, at certain temperatures, conducts electricity utterly without resistance. Until now, all materials that fit the bill could only be pushed toward superconductivity either by adding or removing electrons—but not both.
The new material is the first one ever found that exhibits properties of both of these regimes. The NIST NCNR (Center for Neutron Research) used neutron diffraction to explore the novel material, known only by its chemical formula of YLBLCO.
The material can only be made to superconduct by removing electrons. But if electrons are added, it also exhibits some properties only seen in those materials that superconduct with an electron surplus—hinting that scientists may now be able to study the relationship between the two ways of creating superconductors, an opportunity that was unavailable before this “ambipolar” material was found.
Nature physics – Doped Mott insulators: Breaking through to the other side
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