BCS theory

In physics, the Bardeen–Cooper–Schrieffer (BCS) theory is a microscopic theory of superconductivity which explains many thermodynamic and electromagnetic properties of superconductors. The theory describes superconductivity as a microscopic effect caused by a condensation of pairs of electrons known as Cooper pairs. These pairs move through the lattice without resistance.

The theory is named after John Bardeen, Leon Cooper, and John Robert Schrieffer who proposed it in 1957 while at the University of Illinois. They received the Nobel Prize in Physics for this theory in 1972.

The theory predicts many properties of superconductors such as the energy gap, the isotope effect, and the Meissner effect. Many superconductors can be described entirely by BCS theory and its extensions; these are called conventional superconductors. Unconventional superconductors, on the other hand, cannot be described by BCS theory in entirety. Unconventional superconductors and their relationship with BCS theory is an open research question in condensed matter physics. The theory is also used in nuclear physics to describe the pairing interaction between nucleons in an atomic nucleus.