Superconductors

What is a Superconductor?

Figure 1 - Microphotograph of a superconducting device which measures about a thousandth of a millimetre in size.

Superconductors are amazing materials whose resistance drops to zero when cooled. In other words, very efficient conductors. Commonly used superconducting materials are complex metal oxides (of, for example, yittrium, barium copper oxide) and they typically become superconducting when cooled below around -180 degrees Centigrade. Cooling can be achieved using liquid nitrogen which is cheaply available.

Alongside zero resistance, superconductors also have other useful properties. They are impervious to certain strengths of magnetic field enabling magnetic levitation; superconducting devices called SQUIDS are sensitive magnetic field detectors.

SQUID devices are able to detect magnetic fields 10,000 million times smaller than the Earth's magnetic field. Superconducting microelectronic devices can be made of layers of thin films of superconducting material only a few hundred nanometres thick (Figure 1).

What are they used for? Superconducting electronic devices outperform and are smaller than their traditional counterparts. As parts of communication systems they have application in space exploration, mobile communications and aerospace. For example, a University of Birmingham superconducting filter is installed in the Jodrell Bank radio telescope to filter out atmospheric noise (signals from satellites, television receivers etc). This can dramatically improve the clarity of the images of pulsars, quasars and galaxies received and enables more distant targets with weaker signals to be detected.

A superconducting receiver on trial in mobile phone base stations has the potential to increase the range and reduce the number of mobile phone masts. Magnetic levitation offers exciting possibilities for transport, with a superconducting train which "floats" above the rails already in operation in Japan. Superconducting magnets have for a long time been used in body scanners, but SQUIDS are now used in detection of brain and foetal activity. SQUIDS are also being investigated for application in quantum computers, an emerging breed of super-fast computers.

A member of the superconductivity research team demonstrating coolants to school children.

"The dream is code breaking, super-secure, quantum computers."

Dr Chris Muirhead, School of Physics and Astronomy

Superconductivity at the University of Birmingham The Birmingham Portfolio Partnership is a £6M research grant from The Engineering and Physical Sciences Research Council (EPSRC). The award, entitled "Superconducting Thin Films - Their Science and Applications", is between the School of Engineering and the School of Physics and Astronomy at The University of Birmingham. The research is at the forefront in Europe and in Engineering centres on the invention, production and application of new superconducting materials and devices. The work in Physics develops and applies techniques for investigating and exploiting the properties of these new materials.

Would you like to know more? If you would like to know more about the subject or research, particularly if you would like a school visit, please contact the Outreach Manager for The Birmingham Portfolio Partnership at superconductivity@bham.ac.uk