Physics discovery could enable super-efficient electrical power

An international team of researchers led by Séamus Davis, Professor of Physics at the University of Oxford and University College Cork, have announced results that reveal the atomic mechanism behind high-temperature superconductors, with their findings published in PNAS. Superconductors are materials that can conduct electricity with zero resistance, so that an electric current can persist indefinitely. These are used in various applications, including MRI scanners and high-speed maglev trains; however, superconductivity typically requires low temperatures, limiting their widespread use. The development of super conductors that work at ambient temperatures could revolutionise energy transport and storage.

Certain copper oxide materials demonstrate superconductivity at higher temperatures than conventional superconductors; however, the mechanism behind this has remained unknown since their discovery in 1987. To investigate this, an international team involving scientists in Oxford, Cork in Ireland, the USA, Japan, and Germany, developed two microscopy techniques. The first of these measured the difference in energy between the copper and oxygen atom orbitals, as a function of their location. The second method measured the amplitude of the electron-pair wave function (the strength of the superconductivity) at every oxygen atom and at every copper atom.

Davis said that the researchers visualised the strength of the superconductivity as a function of different devices between orbital energies to precisely measure the relationship required to validate or invalidate one of the leading theories of high-temperature superconductivity, at the atomic scale. As predicted by the theory, the results showed a quantitative, inverse relationship between the charge-transfer energy difference between adjacent oxygen and copper atoms and the strength of the superconductivity.

The researchers believe that this discovery could prove to be a historic step towards developing room-temperature superconductors; these could have far-reaching applications ranging from maglev trains, nuclear fusion reactors, quantum computers, and high-energy particle accelerators, along with super-efficient energy transfer and storage. In superconductor materials, electrical resistance is minimised because the electrons that carry the current are bound together in stable ‘Copper pairs’. In low-temperature superconductors, Copper pairs are held together by thermal vibrations, but at higher temperatures these become too unstable. These results demonstrate that, in high-temperature superconductors, the Copper pairs are instead held together by magnetic interactions, with the electron pairs binding together via a quantum mechanical communication through the intervening oxygen atom.

“This has been one of the Holy Grails of problems in physics research for nearly 40 years. Many people believe that cheap, readily available room-temperature superconductors would be as revolutionary for the human civilisation as the introduction of electricity itself,” Davis said.

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