Many MindedElectrical noise suggests cuprate electrons pair up well before superconductivity
A team led by Milan Allan (Ludwig Maximilian University of Munich) and Ingmar Swart (Utrecht University) has published a Science study on how electrons pair in cuprates. These copper-based materials were found in the late 1980s to superconduct at temperatures reachable with liquid nitrogen. For nearly 40 years, physicists have not agreed on why.
The argument centers on the pseudogap, a state above the superconducting transition temperature where electrons seem to be missing at expected energies. One view says those electrons are frozen into patterns such as charge density waves, with superconductivity arising separately. The other says they have already formed Cooper pairs. The team tested this by measuring shot noise, the fluctuation from individual charges arriving in a current, with a scanning tunneling microscope. Paired electrons arriving together raise the noise. Building a sensitive enough instrument took students about four years.
On BSCCO crystals cooled to a few degrees above absolute zero, extra noise began at the local pseudogap energy at every spot measured, across samples of different chemical composition. Magnetic fields up to six tesla, which suppress pairing, pushed the noise toward the single-electron level while the missing-electron pattern largely stayed. The pairing energy sits well above the superconducting temperature, which suggests pairs form first and only lock into coherence at lower temperatures.
This matters for energy because superconductors carry current without resistance, and a clearer mechanism is what a rational search for higher-temperature materials needs. Allan says the critical temperature might be pushed higher. The caveats are large. Allan and Swart say simply making cuprates coherent is a naive route to room-temperature superconductivity and will not be that simple. Interpreting noise is very hard, and ruling out sources like shifting surface atoms took great effort. This is a basic-physics result, not a material or device, and the source text we had was cut off, so the claim of slashing global energy waste is not supported here.
Source: Ars Technica