Scientists get a clue for superconducting materials

Published: Friday 29 February 2008

power transmission is an endless battle with the phenomenon of resistance, which leads to losses. The search for a superconductor, which offers no resistance to the passage of electricity, has kept many scientists busy.

Superconductors we know already work at extremely low temperatures. In 1986, science found materials that work at relatively higher temperatures. But how they worked was not understood. Now we know.

At room temperature, superconductors do not conduct electricity efficiently as there exists a natural repulsion between electrons. Conduction can happen efficiently only when repulsion between electrons is reduced, and that happens at very low temperatures, at around -253C. In superconductors that work in 'relatively' higher temperatures of around -140C, the process of conducting electricity does not depend on the attraction between the electrons, says a recent theory from the California Institute of Technology. Instead, the electrons align themselves in a manner that creates a magnetic field. The attraction between the electrons and the magnetic field conducts electricity. This shows where and how to look for new classes of superconducting materials, says David Pines, the lead author of the study published in the December 27 issue of Nature (Vol 450, No 20).

Hope in oxides But what is this class of materials? They are complex oxides, like those of bismuth, strontium, calcium and copper in the form of one compound--Bi2Sr2Ca1Cu2O8+.

Those who buy this theory are excited. "If superconductivity's mechanism is understood well in these oxides, it will pave the way for identifying materials that conduct electricity more efficiently," says V Sankarnarayan, a scientist at iit Madras. This knowledge can also help magnetic resonance imaging and magnetic ore filtering technologies.

Not everybody accepts the magnetic field's criticality in superconductivity. G Bhaskaran of Chennai-based Indian Institute of Mathematical Sciences says the electron-magnetic field attraction in the oxides is not the reason for better conductivity at high temperatures. He says vibration between bonds in the oxide structure plays an important role in superconductivity.

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