Breakthrough in Superconductor Theory
Physicists from King's College London and collaborating institutions have developed a new approach explaining high-temperature superconductivity in certain materials. Their research, published in Nature, focuses on cerium superhydride (CeH9), identifying a previously overlooked factor contributing to its superconductivity.
Cerium Superhydride's Enhanced Performance
The discovery indicates that CeH9 can operate at temperatures twice as high as earlier predictions. This advancement provides a foundation for computational efforts to discover room-temperature superconductors.
The Challenge of Superconductivity
Superconductors can enable near-zero energy loss in electric technologies, addressing growing energy demands. However, most known superconductors require extremely low temperatures (below -196°C), making them costly and impractical for widespread use. Hydrogen-rich compounds have shown the highest operational temperatures, with LaH10 reaching approximately -23°C, but under extreme pressures comparable to Earth's core.
Resolving Theoretical Discrepancies
Previous theories accurately described LaH10 but failed to explain other hydride superconductors like CeH9, which functions at lower, more practical pressures. Dr. Yao Wei, a former PhD researcher at King's, noted the significant challenge in describing CeH9's superconductivity.
The Role of Electron Scattering
The research revealed that alongside the known phonon-electron interactions (vibrating lattice interacting with electrons), electron-electron interactions, or electron scattering, are critical for CeH9's superconductivity. CeH9 presents complexity due to its numerous heavy electrons. Dr. Jan Tomczak, Senior Lecturer in Physics, likened Ce-borne electrons to "viscous honey" due to significant repulsion and scattering.
Mechanism of Enhanced Superconductivity
Electron scattering reduces electron energy. A higher number of negatively charged, low-energy electrons increases the shielding of positive nuclei, reducing their repulsion. Professor Samuel Poncé explained that this effectively "softens" the atomic lattice, facilitating vibrations. The combination of low-energy electrons and soft phonons is key to this enhanced superconductivity.
Validation and Future Tools
By incorporating the effect of electron scattering, which is a complex quantum many-body problem, the researchers eliminated a 50% discrepancy between experimental data and prior theoretical models, achieving a 1% accuracy in reproducing the transition temperature. The team states that this new computational tool can accelerate the exploration and discovery of phonon-mediated superconductors capable of functioning at high temperatures and lower pressures.