How to Make Gold and Copper Conduct Without Resistance express
Electrons in a conductor are like a chaotic crowd: colliding, they lose energy, and resistance arises. In a superconductor, however, they move in unison, like partners in a well-coordinated dance, without touching each other. This state has reduced entropy — meaning disorder.
Such behavior is rare for gold and copper. But in layers just two to three atoms thick for copper or five for gold, electrons synchronize with atomic vibrations, and resistance vanishes. The trouble is that this requires cooling below 1 K using helium.
The breakthrough came from a boron nitride insulator placed on a copper film. If you join the layers through boron atoms, the superconducting temperature is 3.23 K. But rotating the crystal so that the bond goes through nitrogen raises it to 7 K. The reason is a change in the "Fermi surface" — the boundary of filled electron states. It resonates with the atomic lattice, sharply enhancing the needed interaction. John Bardeen predicted the electron pairing mechanism back in 1957, and spectroscopy today allows us to observe these effects directly.
Gold atoms are so massive that their vibrations usually cannot adjust to electrons. But in a film five atoms thick — like the thinnest foil — they become pliable and join the common rhythm.
Stanisław Lem in 'Solaris' described metamaterials whose properties depended on thickness — like these superconducting layers.