High-temperature superconductors: magnetic glue may be the clue

Striking pictures of magnetic waves inside advanced ceramics may be the clue to understanding how they can transmit electricity without losing energy, according to results obtained by two teams of scientists using the UK’s world-leading ISIS neutron source in Oxfordshire and published this week in the journal Nature.

The ceramics, known as high-temperature superconductors, lose all resistance to the flow of electricity when cooled below a critical temperature. Wires made from the ceramics can conduct up to 140 times more power than conventional copper wires of the same dimension, carrying current with 100% efficiency. Yet despite their growing use in applications ranging from medical imaging scanners to revolutionary propulsion systems, just exactly how they work remains a mystery.

What is astonishing in the results of the two research teams led by Professor Stephen Hayden at the University of Bristol in the United Kingdom, and Dr. John Tranquada at the US Department of Energy’s Brookhaven National Laboratory, is the almost identical data obtained from their two different ceramics. Electric current is carried most efficiently in the materials when the electrons are ‘glued’ into pairs. Both teams believe they have observed the fingerprint of what might be the binding glue.

“Without the unique capabilities of the MAPS experiment at the ISIS neutron source these observations would have been impossible,” said Dr Toby Perring, Project Scientist for the MAPS instrument at the Rutherford Appleton Laboratory, and a co-author on both of the Nature papers. “The 100 million detector pixels gives an unmatched clarity of vision into the interior world of superconductors.”

“The results suggest that the glue may be due to very weak magnetism associated with embedded copper atoms. The electrons appear to be bound together by a sort of magnetic glue,” explained Stephen Hayden.

Whilst the results will cut a swathe through the huge number of competing explanations in existence, each team is currently backing their own favourites, and the impact of their results will certainly be intensely debated.

“We definitely expect some controversy,“ says John Tranquada from the Brookhaven team, “because our data suggest that some popular ideas are wrong.”