BARDEEN COOPER AND SCHIEFFER THEORY
A microscopic theory of superconductivity was developed in 1957 by John Bardeen, Leon Cooper & Robert Schrieffer, which is known as the BCS theory. The central feature of the BCS theory is that two electrons in the superconductor are able to form a bound pair called a Cooper pair if they somehow experience an attractive interaction between them. electrons normally repel one another because of their like charges. This may be thought of in the following way and is illustrated in Figure.
COOPER PAIR FORMATION