Almost 100 years ago, K. Onnes succeeded in liquefying Helium, finding it boiled at 4.2K. Many remarkable discoveries of quantum properties of Liquid Helium followed, but one discovery was Superconductivity. He found that below a certain termperature, lead and tin, and some other metals lost all resistance. How can it be? BCS (three guys) explained it as one electron distorting the lattice slightly, and another one with opposite spin joins (and aids) it, to form a pair: “Cooper pair.” Pauli Principle tells us that no more than a pair can play this game.

• Almost 100 years ago, K. Onnes succeeded in liquefying Helium, finding it boiled at 4.2K. Many remarkable discoveries of quantum properties of Liquid Helium followed, but one discovery was Superconductivity. He found that below a certain termperature, lead and tin, and some other metals lost all resistance. How can it be? BCS (three guys) explained it as one electron distorting the lattice slightly, and another one with opposite spin joins (and aids) it, to form a pair: “Cooper pair.” Pauli Principle tells us that no more than a pair can play this game.

• We’ll exaggerate for a picture:

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