When electrons couple up, further quantum trickery makes superconductivity unavoidable. Normally, electrons can’t overlap, but Cooper pairs follow a different quantum mechanical rule; they act like particles of light, any number of which can pile onto the head of a pin. Many Cooper pairs come together and merge into a single quantum mechanical state, a “superfluid,” that becomes oblivious to the atoms it passes between.
BCS theory also explained why mercury and most other metallic elements superconduct when cooled close to absolute zero but stop doing so above a few kelvins. Atomic ripples make for the feeblest of glues. Turn up the heat, and it jiggles atoms and washes out the lattice vibrations.
Then in 1986, IBM researchers Georg Bednorz and Alex Müller stumbled onto a stronger electron glue in cuprates: crystals consisting of sheets of copper and oxygen interspersed between layers of other elements. After they observed a cuprate