The Breakthrough
Spring 1957. Iowa City, Iowa. The kind of place where nothing happens—until something changes everything.
John Bardeen was already a legend. In 1956, he and Brattain and Shockley had invented the transistor at Bell Labs, replacing the fragile vacuum tube with something solid. The transistor won them the Nobel Prize that year. Bardeen was the youngest Nobel laureate in physics at the time.
But Bardeen was restless. He turned to superconductivity—a phenomenon known since 1911, when Heike Kamerlingh Onnes discovered that mercury's resistance vanished at 4.2 Kelvin. Forty-six years of data, of phenomenological theories, of Ginzburg and Landau's beautiful but hand-wavy approach. Nobody had a microscopic theory.
Walter Cochran, a graduate student under Bardeen, was calculating how electron-phonon coupling might affect electron effective mass. The coupling between electrons and phonons—the way an electron's passage distorted the lattice and that distortion affected other electrons—was the frontier.
Bardeen read Cochran's calculations. Something clicked.
The math suggested that, under certain conditions, electron-phonon interaction might actually create an attractive force between electrons. This made no sense. Electrons repel. One of the most fundamental facts of nature. But the crystal lattice—alive with phonons—could transmit attraction.
Bardeen didn't sleep that night. He called a colleague: "We might have an explanation for superconductivity."
He brought in Robert Schrieffer, a 22-year-old graduate student carrying a suitcase full of equations—his own calculations that bore an eerie resemblance to what Bardeen was developing.
The three of them—Bardeen, the cautious genius; Leon Cooper, who had developed the mathematical framework for paired electrons; and Schrieffer, the young prodigy—worked like a machine.
The breakthrough came in May 1957. Schrieffer had the key insight: a wavefunction describing the superconducting state as a collective state of paired electrons. The BCS wavefunction—a coherent superposition of states with different numbers of particle pairs—was mathematically elegant.
Bardeen and Schrieffer spent the night of May 19 working on the paper. By morning, it was done. Sent to Physical Review Letters. "Theory of Superconductivity"—23 pages containing the entire microscopic theory.
BCS theory explained everything: the energy gap, the critical temperature, the isotope effect, the specific heat jump. Every experimental observation puzzling physicists for 46 years fell into place.
Nobel Prize in 1972. Bardeen, Cooper, and Schrieffer shared it. Bardeen became the only person to win the Nobel Prize in physics twice.
The deeper story: BCS showed that complex collective behavior, that no individual electron could display alone, could be understood from first principles. Phonon-mediated pairing. Trillions of Cooper pairs condensing into a single quantum state. A state flowing without resistance through a crystal lattice.
The theory inspired applications elsewhere. Superfluid helium-3. Color superconductivity in neutron stars. The Higgs mechanism in particle physics is a relativistic version of Cooper-pairing.
Written by a 22-year-old and his advisor, in an office in Iowa City, on a night in May 1957. Nothing happens in Iowa City. Until it does.