One of the outstanding mysteries in condensed-matter physics is that the most perfect conductors so far discovered―the high-temperature superconductors―are more like insulators than metals. Superconductivity, the flow without resistance of current through some materials, usually only occurs at very low temperatures. Conventional superconductivity develops in metals, but high-temperature superconductivity (at about 90 K) occurs in insulating copper oxide ceramics when small amounts of charge are injected by chemical doping. In Physical Review Letters, Fu Chun Zhang provides a fresh perspective on this strange phenomenon by unifying alternative views of how high-temperature superconductivity is linked to an insulating state of matter. According to Zhang, an undoped copper oxide superconductor can, under certain conditions, transform from its insulating state into an extremely delicate state of 'gossamer' superconductivity.
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