Superconductors were one of the twentieth century's greatest scientific discoveries, but their potential to revolutionise technology is only just being realised.
By Helen Massy-Beresford
'The history of superconductivity reminds me of gold prospecting in nineteenth century California,' says Professor of Physics, Stephen Blundell.
'There’s a lot of hacking through unpromising rock, and then the cry goes out ‘there’s gold in them there hills’ and everybody rushes with their hammers and chisels,' he says. Instead of gold, researchers are on the hunt for new materials showing superconductive properties.
Superconductors are already used in MRI equipment and have great potential, for example to help make energy transmission more efficient. However scientists first need to find materials that have superconductive properties at higher temperatures.
'The holy grail is getting superconductivity to room temperature,' says Blundell, also the author of Superconductivity: A Very Short Introduction (published by Oxford University Press) after he spotted a gap in the popular market for a book on the physics of materials.
'When superconductivity was discovered in mercury in 1911, it was very much a low temperature phenomenon – the record was 4 degrees above absolute zero. It currently stands at 200 degrees above absolute zero at very high pressure. That’s about -70 degrees Celsius. There’s no reason now for superconductivity not to work at room temperature. If you plot a graph from 1911 to the present day you see a steady increase.'
Understanding how superconductivity works is essential to finding new superconductors, Blundell says.
'In the 1980s it looked as if everything had been discovered and then ceramic materials were discovered. We still don’t know how ceramics work in detail. There are a lot of fundamental questions that need to be resolved.'
Ceramic materials are known as high temperature superconductors – the materials that so far show superconductive properties at the highest temperature. Oxford is playing an important role in superconductor research – and collaboration between departments sets it apart, Blundell says. 'One thing I’ve found at Oxford is that it’s a place where friendly collaborations thrive very easily. It’s not a place with too many big egos and there’s a lot of interest in not being limited by your discipline boundaries.'
The Departments of Physics and Chemistry departments have been working closely on the discovery of superconductivity in a family of iron compounds – previously thought to be impossible because iron is magnetic. To tackle the problem, Blundell has teamed up with Simon Clarke, Professor of Inorganic Chemistry.
'We’ve been doing a lot of work together on trying to understand the physics of these materials and to find new ones,' Blundell says.
'It was thought that because iron was magnetic it was the enemy of superconductivity. The big breakthrough we’ve had is finding a way of inserting molecules between the layers. Most of these materials are layered materials – we’ve found a way of inserting a particular molecule in between the layers. That increased the temperature at which they were superconducting by more than a factor of four – a huge increase. A lot of our recent work has been on trying to understand that effect.'
Work with the Department of Materials, along with funding from within the university and via a local enterprise partnership, for a Centre for Applied Superconductivity, has opened up the opportunity to make use of links with local industry.
'One of Oxford’s first spin-out companies was Oxford Instruments, one of the world’s leading manufacturers of superconducting magnets,' says Blundell.
Oxford Instruments is still headquartered near Abingdon and Siemens Magnet Technology, which Siemens bought from Oxford Instruments, makes MRI magnets in Eynsham.
“We have all that expertise industrially surrounding Oxford and that means I think we’re a very intense technological hub where superconducting technology has been invented and nurtured and manufactured.”