Recently, King’s College London (KCL) physicists and their collaborators developed a novel theory, explaining how a class of superconductors functions at high temperatures.
Superconductors are materials that conduct electricity with zero resistance below a limiting “critical” temperature, therefore minimising energy loss.
This makes them optimal for serving the world’s rising energy demands. They also frequently operate in everyday technology such as MRI (magnetic resonance imaging) scanners.
This discovery concentrates primarily on the chemical compound cerium superhydride (CeH9) and was published in npj Computational Materials.
The study pinpoints the reason for the material’s superconductivity – electron scattering. It reveals the superconductor can operate at a temperature double the one originally predicted and could help curate a computational search for room temperature superconductors.
Most superconductors can only function at extremely low temperatures – at least -196ºC – making them uneconomical and impractical for widespread utilisation.
For decades, physicists have been looking for room-temperature superconductors. Numerous hydride superconductors operating at more economical pressures are not explained by the older superconductivity theory.
Therefore, physicists and researchers from KCL, the University of Cambridge, Vienna University of Technology and the Université catholique de Louvain searched for a more profound theory. They selected the compound cerium superhydride (CeH9) for the investigation.
Originally, it was believed that the superconductivity of CeH9 (cerium superhydride) stems from how the crystal’s uniform “lattice” structure vibrates and produces phonons (waves transporting heat and sound) which interact with electrons.
The researchers discovered that, instead of the phonon-electron interactions, electron-electron interactions (electron scattering) actually catalysed the better-than-expected superconductivity. Phonons are like packets of sound wave energy.
The crux of their findings is that electron scattering depletes the electrons’ energy – and that the abundance of electrons with lower energy and higher magnitude of negative charge causes the nuclei’s positive charges to be shielded. This causes nuclei (the core of an atom) to repel each other less.
“The atomic lattice of the crystal can be compared to an array of masses connected with springs – these springs have now become softer, facilitating vibrations. Low-energy electrons and soft phonons are the key ingredients to the superconductivity, and we just got more of both!”
Samuel Poncé, Professor at Université catholique de Louvain, quote from KCL website
The team believe this framework is applicable to several other systems and could be utilised in modelling phonon-based superconductors that operate at even higher temperatures.
Additionally, the results of this study have possible applications for machine learning that can reveal superconducting materials. However, the possibilities of chemical and structural combinations are too vast to generate every possible material for superconductivity determination in the lab.
“Our computational tool could help simulate synthetic data on different crystal structures and chemical compositions – to build a data set on which to train neural networks. ML could then be used to find optimal solutions to the temperature and pressure challenges, finetuning structures and combinations, and helping us work out which direction to take.”
Dr Jan Tomczak, Senior Lecturer in Physics at King’s College London, quote from KCL website
This study conducted by research physicists from various universities, including KCL, has uncovered the influences of previously underestimated properties that influence superconductivity.
It has major implications for superconductor research and discovery, and could prove beneficial in numerous industries in the future.
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