Newspaper article The Daily Yomiuri (Toyko, Japan)

The Quest to Understand Superconductivity

Newspaper article The Daily Yomiuri (Toyko, Japan)

The Quest to Understand Superconductivity

Article excerpt

What mechanisms create states of superconductivity, in which a material's electrical resistance shrinks to zero?

Ever since the phenomenon of superconductivity was discovered in 1911, physicists have been tackling this challenge. Some have even called it "the most difficult problem left over from the 20th century." The discovery of a new high-temperature superconductor by Japanese researchers in 2008 catalyzed research aimed at answering this question.

Reducing loss

Japan generates about 800 billion kilowatt-hours of electricity every year to power homes and businesses. However, 5 percent of this, or 40 billion kilowatt-hours, is lost in the form of heat, for reasons such as electrical resistance in power lines.

If superconductive power lines could be created, it would greatly cut down on the amount of electricity lost.

Research in this field accelerated after the 1986 discovery of a superconductive substance in "cuprate," which is a type of ceramic. Until then, research had focused mainly on metals such as mercury and niobium. Research focused on these new superconductors, and in 1993, scientists succeeded in achieving superconductivity at an absolute temperature (see below) of 135 Kelvin (minus 138 C). Until then, superconductivity had only been possible at 30 Kelvin (minus 243 C) or below.

The mechanism of superconductivity in metal was solved in the mid-20th century, and the theory is that at normal atmospheric pressure, superconductivity cannot occur at 40 Kelvin or higher.

Why this theory does not hold for ceramic high-temperature superconductors is largely a mystery.

"Solving that would help us design even better superconductors," said Shibaura Institute of Technology President Masato Murakami, who specializes in superconductor engineering.

Making pairs

Electric currents are transmitted by the flow of electrons inside a substance.

Normally, electrons move individually. Since they are negatively charged, they are attracted to any positively charged ions in the substance, which disturbs their movement. This is the cause of electrical resistance.

However, if two electrons form a pair, it completely changes how they move.

"They become more like waves than particles, and move smoothly through the substance," said Takasada Shibauchi, an expert in materials science at the University of Tokyo. "The problem is determining the true structure of the 'glue' that ties two electrons together. …

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