An international team of researchers has collaborated to perform a landmark experiment which could revolutionise the future of new technology.
Professor Andy Mackenzie from the University of St Andrews has worked alongside physicists from the University of Bristol and the High Magnetic Field Laboratory in Toulouse, France in a search for one of the ‘Holy Grails’ of modern science – how to make a superconductor work at room temperature.
Superconductivity is one of the most spectacular physical phenomena ever discovered and operates at exceptionally low temperatures. When certain metals are cooled, they suddenly change their properties, becoming perfect conductors of electricity and expelling magnetic fields so that no energy is ever lost.
The researchers have taken one step closer to making superconductivity appear at room temperature in a discovery that could transform a whole range of environmentally relevant technologies such as energy transmission and storage.
Prof Mackenzie explained, “This work is something of a triumph of perseverance. One of the main barriers to progress in the field has been the fact that some experiments that are key to understanding high temperature superconductivity are notoriously difficult to perform.”
Over the past year a number of important advances in the field of superconductivity have been made around the world, but these still left gaps in our knowledge. Now the international team of physicists has managed to fill one of these gaps, detecting ‘quantum oscillations’ (one of the most useful indicators of how such superconductors form) in a series of high precision measurements on an exotic high temperature superconductor.
Professor Mackenzie commented, “Looking for this signal is like searching for a very small needle in a very large haystack, and we have all tried to find it in many different experiments. It has only become possible because of some wonderful technical advances led by Cyril Proust at Toulouse. We feel a real sense of collaborative achievement.”
The experiments require exquisitely pure crystals and extremely large magnetic fields, and laboratories all over the world have been struggling for two decades to achieve the right combination of circumstances.
“My Bristol colleagues Nigel Hussey, Tony Carrington and I identified the material with the highest chance of yielding this result as young students and post-docs at Cambridge nearly twenty years ago,” said Professor Mackenzie, “and I grew the crystals on which this year’s experiment succeeded as long ago as 1993”.
In traditional superconductors the tactic was to destroy the superconductivity by raising the temperature or applying a magnetic field and then perform low temperature experiments on the parent metal. In the new materials this is particularly problematic because the superconductivity is so difficult to destroy – it protects itself from precisely the experiments that might be the key to understanding it.
Superconductors already play a key role in some technologies such as the filtration of the china clays that are used in every piece of glossy paper in the world. Until 1986, superconductivity was thought to occur only at extremely low temperatures comparable to that of interstellar space. Then, an entirely new class of complex materials was discovered in which superconductivity appeared at -150 ºC.
Such high temperature superconductors raise the hope of someday making superconductivity appear at room temperature. If this could be achieved, it would revolutionise energy transmission and storage amongst other environmentally relevant technologies.
Professor Mackenzie continued, “The project has benefited enormously from the long-term, blue skies support provided by a Portfolio Partnership grant from the Engineering and Physical Sciences Research Council for collaborative work in the field between Bristol, Cambridge and St Andrews.”
The team’s breakthrough is described in the 16 October issue of the journal Nature.
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Ref: Holy Grail 21/10/08
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