Feynman Lectures Simplified 3C

Excerpt:

Cooper Pairs

The phenomenon of electric current flowing without resistance derives from a remarkable behavior of electrons flowing in crystals at very low temperatures.

Physicists were initially quite surprised to discover that electrons can bind together in any fashion. They are negatively charged particles that repel one another, and they are identical fermions that cannot share a common state. In isolation, these facts certainly preclude electrons binding to one another. But, in the more complex environment of solid matter, other considerations apply.

In very simplified terms, as an electron moves through a crystal (a solid with a regularly repeating pattern of atoms), its negative charge attracts atomic nuclei and repels lattice electrons, resulting in a very slight shift of net positive charge, as sketched below.

Black dots represent net positive charges, and open circles represent electrons flowing through the crystal, with their velocities indicated by arrows. Positive charges moving toward the right-hand electron, and negative charges moving away from it (not shown in figure), create a small region of net positive charge. That positive charge attracts the left-hand electron, facilitating its passage through the crystal.

Guide to the Cosmos
Making the Wonders of our Universe
Accessible to Everyone

Robert L. Piccioni, Ph.D.