Superconductivity above the boiling point of liquid nitrogen was discovered in copper-oxide ceramics in 1986, but unlike low-temperature superconductivity, no accepted theory explains why electrons pair and flow without resistance at such comparatively high temperatures. The mechanism remains, in the field's own words, an important unsolved theoretical problem in condensed matter physics.
What would resolve this A microscopic theory of high-temperature superconductivity that predicts, rather than merely fits after the fact, which materials will superconduct and at what temperature, tested against the growing family of known high-temperature superconductors.
OpenCondensed matter physicsPhysics (Wikipedia)