Physicists listened to electrical noise to crack a superconductor mystery
Tuning in to electronic noise can tell us whether electrons have paired up or not.
Superconductors enable electricity to flow without resistance, yet most only function a few degrees above absolute zero. In the late 1980s, cuprates—copper-based materials—were discovered to superconduct at higher temperatures attainable with affordable liquid nitrogen. Despite ongoing research spanning nearly 40 years, physicists remain divided over the underlying reasons.
A recent Science study led by Milan Allan of the Ludwig Maximilian University of Munich and Ingmar Swart of Utrecht University in the Netherlands has provided some insights by detecting the faint electrical noise produced by current flowing into a cuprate. The puzzling electrons Central to the enigma of cuprates’ high-temperature superconductivity lies in a peculiar state known as the pseudogap.
Allan explained, “The pseudogap is a phenomenon of missing electrons.” Above the temperature at which cuprates transition to superconductivity, certain electrons appear to disappear—measurements reveal significantly fewer of them at the energy levels where they should be. “Everybody knows that from different probes, you see that there’s these vanishing electrons, but nobody knows why,” Allan stated.
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