Séamus Davis, a professor of physics at the Universities of Oxford and Cork, is the head of an international research group that has just released findings shedding light on the atomic mechanism underlying high-temperature superconductors. The results are presented in PNAS.
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Superconductors are substances that can conduct electricity without experiencing any resistance, allowing an electric current to flow without interruption. Superconductivity typically necessitates extremely low temperatures, restricting its widespread use.
Superconductors are already employed in various applications, including MRI scanners and high-speed maglev trains. The development of superconductors that function at room temperature is one of the main objectives of physics research since it could revolutionize energy storage and transportation.
Following their discovery in 1987, certain copper oxide materials have demonstrated superconductivity at temperatures greater than ordinary superconductors, but the mechanism underlying this has remained a mystery.
Two novel microscopy techniques were created to investigate this by an international team of researchers from Oxford, Cork, Ireland, the USA, Japan, and Germany.
The first calculated the energy difference between the orbitals of the copper and oxygen atoms about their relative positions. The second assessed the strength of superconductivity (the amplitude of the electron-pair wave function) for each copper and oxygen atom.
By visualizing the strength of the superconductivity as a function of differences between orbital energies, for the first time, we were able to measure precisely the relationship required to validate or invalidate one of the leading theories of high-temperature superconductivity, at the atomic scale.
Séamus Davis, Professor, Physics, Oxford University
According to the theory’s predictions, the data revealed a quantitatively invertible connection between the strength of the superconductivity and the charge-transfer energy distinction between nearby oxygen and copper atoms.
The research team believes this finding could represent an important milestone in developing room-temperature superconductors. Ultimately, these might be used for various applications, such as super-efficient energy storage and transfer, quantum computers, nuclear fusion reactors, and high-energy particle accelerators.
Due to the robust “Copper pairs” in which the electrons that carry the current are bound, the electrical resistance is restricted in superconductor materials. Thermal vibrations hold Copper couples in low-temperature superconductors, but these become too unsteady at elevated temperatures.
These new findings show that the Copper pairs are not bound together through magnetic interactions in high-temperature superconductors but rather by a quantum mechanical interaction between the electron pairs and the oxygen atom in between.
Professor Davis said, “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 civilization as the introduction of electricity itself.”
O’Mahony, SM, et al. (2022) On the electron pairing mechanism of copper-oxide high-temperature superconductivity. PNAS. doi.org/10.1073/pnas.2207449119.