Fifty Years of BCS Theory, Yet Superconductivity Puzzles Remain

An article in the New York Times discusses an extraordinary breakthough in the physics of solids a bit more than 50 years ago.

Superconductivity had been discovered in 1911 by Heike Kamerlingh-Onnes, who won the Nobel Prize two years later for his work at extremely low temperatures.

But it took decades before developments in the quantum theory of solids put University of Illinois professor John Bardeen and his students Leon N. Cooper and J. Robert Schrieffer on the track of its theoretical underpinnings–coupled conduction electrons, or Cooper pairs, that exchanged quanta of vibrational energy called phonons, enabling them to pass through a crystal without losing any energy.

That discovery, soon named the BCS theory after the initials of the three men’s last names, came in 1957, the same year in which Bardeen shared the Nobel Prize in physics with Walter Brattain and William Shockley for the invention of the transistor. Although Nobel committees of later years might have been reluctant to give a repeat prize to Bardeen, it would have meant bypassing Cooper and Schrieffer. So in 1972, the three were honored with the second Nobel Prize for work that involved the odd but technologically important phenomenon.

In the following year, 1973, Brian Josephson won the Nobel for a technologically important superconductivity-related effect that he predicted and bears his name.

Then in 1986, a new class of ceramic “high-temperature” superconductors (HTS) burst on the research scene. A year later, the discoverers of those materials, J. Georg Bednorz and K. Alexander Mueller, won yet another superconductivity-related Nobel.

Though theoretical physicists have been grappling with many possibilities, no one has yet come up with the equivalent of Cooper pairs or BCS theory for HTS. If it takes 46 years post-discovery, as the BCS theory did, we can expect a breakthrough in 2032 and a Nobel prize soon afterward.

Physicists and technologists are hoping it will come much sooner than that.

For more about the work of Bardeen, Cooper, and Schrieffer, please read my Physics : Decade by Decade in the Facts on File Twentieth Century Science reference set. John Bardeen is the “Scientist of the Decade” for the 1950s, and that profile captures not only the scientific achievements but also the personal warmth of the only person ever to win two Nobel Prizes in the same field.