Superconductivity: Further Outlook Warmer

66 EE April 1988 SUPERCONDUCTIVITY: FURTHER OUTLOOK WARMER by George Short London"s Science Museum recently acquired a new exhibit. It is not much to look at: a cylinder of black ceramic material. But the small company from the London suburbs which made it is proud to claim that it is the world"s first high-temperature superconducting solenoid. It is just one manifestation of the burst of research activity into a new class of superconductive materials. Superconductivity is the property of cer- tain materials to lose all electrical resist- ance. The phenomenon was discovered by the Dutch physicist Heike Kammerl- ingh Onnes, who announced in 1911 that mercury becomes superconductive when cooled to a very low temperature, about four degrees above absolute zero (4 K). It soon emerged that a number of metals become superconductive when cold enough. In every case the temperature re- quired was only a little above absolute zero, attainable in practice only by im- mersing a specimen in li...