Cooper, Leon Niels (1930- )

US physicist who in 1955 began work on the phenomenon of superconductivity. He proposed that at low temperatures electrons would be bound in pairs (since known as Cooper pairs) and in this state electrical resistance to their flow through solids would disappear. He was awarded the Nobel Prize for Physics in 1972 for his work on the theory of superconductivity. He shared the award with John Bardeen and J Robert Schrieffer.

Cooper was born in New York, where he attended Columbia University, specializing in quantum field theory - the interaction of particles and fields in subatomic systems. His work with John Bardeen was carried out at the University of Illinois. In 1958 Cooper moved to Brown University, Rhode Island, and in 1978 became director of the Centre for Neural Science at Brown.

Whereas the decrease in resistance is gradual in most metals, the resistance of superconductors suddenly disappears below a certain temperature. Experiments had shown that this temperature was inversely related to the mass of the nuclei. Cooper showed that an electron moving through the lattice attracts positive ions, slightly deforming the lattice. This leads to a momentary concentration of positive charge that attracts a second electron. This is the Cooper pair. Although the electrons in the pair are only weakly bound to each other, Bardeen, Cooper, and Schrieffer were able to show that they all form a single quantum state with a single momentum. The scattering of individual electrons does not affect this momentum, and this leads to zero resistance. Cooper pairs cannot be formed above the critical temperature, and superconductivity breaks down.

Developing a theory of the central nervous system, Cooper has also worked on distributed memory and character recognition.

He published The Meaning and Structure of Physics (1968).