- Person
- Leon Cooper
- Lived
- 1930–2024
- Field
- Theoretical physics, neuroscience
- From
- American
The story
Leon Cooper was born in the Bronx in 1930 to Jewish immigrants from Belarus and Poland, and went from the Bronx High School of Science to a doctorate at Columbia. In 1955 John Bardeen of the University of Illinois, co-inventor of the transistor, recruited him to work on one of the great unsolved puzzles of physics.
In 1911 Heike Kamerlingh Onnes had discovered that mercury cooled near absolute zero loses all electrical resistance. Other metals did the same, and superconductors also expelled magnetic fields, but for more than forty years no one could explain why. Electrons repel each other, and in ordinary metals they constantly collide with the vibrating atoms of the crystal, which is what causes resistance.
In 1956 Cooper showed in a short paper in Physical Review that even a weak attraction between two electrons, of the kind the vibrating lattice can provide, binds them into a pair when they move among the other electrons of a metal. In 1957 Bardeen, Cooper and Schrieffer built on these Cooper pairs a complete theory, known as BCS. Below a critical temperature, vast numbers of pairs condense into a single quantum state, and because breaking a pair costs a definite amount of energy, ordinary collisions cannot slow them. The current flows without resistance. The theory also explained the expulsion of magnetic fields, the energy gap and the dependence of the critical temperature on the mass of the atoms.
BCS theory explains the conventional superconductors, including the niobium–titanium alloy in most superconducting magnets. Those magnets are at the heart of hospital MRI scanners, which in 2014 accounted for about four fifths of the roughly six billion dollars of economic activity that depended on superconductivity. They are also used in NMR machines that chemists use to work out molecular structures, and in particle accelerators such as the Large Hadron Collider. The idea of pairing spread to nuclear physics and beyond. Bardeen, Cooper and Schrieffer shared the 1972 Nobel Prize in Physics; Cooper later turned to neuroscience at Brown University.
Why it matters
The BCS theory built on Cooper pairs explains how the superconducting magnets in MRI scanners, NMR machines and particle accelerators work.
About Leon Cooper
Bronx-born physicist whose “Cooper pairs” explained superconductivity, the physics behind MRI magnets, and who then pioneered mathematical models of how the brain learns.
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Sources
- BCS theory Wikipedia
- Superconducting magnet Wikipedia
- Passages: Nobel Prize winner and Brown professor of physics Leon Cooper Brown University
- Leon Cooper Wikipedia
Another act of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.