https://phys.org/news/2018-07-similarity-stripy-black-holes-high-temperature.html

All relatively high-temperature superconductors now known are based on so-called Mott insulators. These form when electrons are stuck in their crystal lattice nodes, exactly one per node. They turn into superconductors after extra electrons are injected. Researchers don't understand why this happens on a fundamental level. Knowing this could enable even higher-temperature superconductors that are cheaper to keep sufficiently cool.

As the superconductor is formed, the imparity between the number of electrons and the number of available nodes within the crystal lattice causes a stripy pattern, much like the moving Moiré patterns seen on TV when an old-fashioned computer screen is filmed. But why? This is a key question in understanding Mott insulators.