Magazine article Science News

Superconductors with Electrons in Charge

Magazine article Science News

Superconductors with Electrons in Charge

Article excerpt

Superconductors with electrons in charge

The discovery of a new family of ceramic superconductors that lose all resistance to the flow of electrical current at a lowly 24 kelvins (-416[deg.]F) seems a much less glamorous result than achieving a record-high superconducting transition temperature. Nevertheless, these new compounds, in which electrons carry the superconducting current, may provide important clues that how high-temperature superconductors work. In all previously known examples, "holes" (the absence of electrons) in the electronic structure of the material's crystal lattice are responsible for the superconducting current.

Discovered by Yoshi Tokura and his colleagues at the University of Tokyo, the new compounds contain copper, oxygen, the rate-earth element cerum and any one of three lanthanides: lanthanum, praseodymium or samarium. The researchers describe their compounds in the Jan. 26 NATURE.

All high-temperature superconductors made to date contain layers of copper and oxygen atoms. Normally, each copper atom is surrounded by five or six oxygen atoms. Four oxygen atoms lie in the same plane as the copper atom, and the remaining oxygen atoms sit above and/or below the copper atom. In the new compounds, the top and bottom oxygen atoms are absent, leaving only the copper-oxygen planes. The introduction of cerium in place of the elements used in previously discovered superconductors provides extra electrons. For superconductivity to occur, theorists believe these electrons must pair up despite the fact electrons have like charges and naturally tend to repel each other. …

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