The first scientist to receive the Nobel awards twice in the same field

John Bardeen was a key participant in two fundamental discoveries in recent physics having immense promise and practical consequence. Working at the Bell Laboratories after World War II, Bardeen was one of three central figures in the development of the transistor, which within a few years became a crucial component everywhere in electronics technology. During the 1950s Bardeen also discovered a theoretical solution to the problem of superconductivity-the property of certain metals at low temperatures to lose all resistance to electrical conduction.

The BCS theory (named for Bardeen, Leon Cooper, and John R. Schrieffer) became the basis for research that continues today, promising new technologies with enormous and global economic impact. Highly efficient superconducting motors, generators, and other machines hold the potential, in the twenty-first century of revolutionary advances in electronics.

John Bardeen was born on May 29, 1908, in Madison, Wisconsin. His father, Charles Russell Bardeen, was a professor of anatomy who became dean of the University of Wisconsin Medical School. His mother, Althea Harmer Bardeen, was a teacher and an artist who died when John was an adolescent.

Encouraged academically by his parents, Bardeen excelled in school, taking algebra at age ten, and he was skipped ahead in grade several times. He attended the University of Wisconsin beginning in 1923, at age fifteen, where he became interested in mathematical physics under the influence of the visiting PAUL.

DIRAC . However, he received his bachelors degree in engineering in 1928 and his master degree in 1929.

For several years during the Great Depression, Bardeen worked as a geophysicist with the Gulf Research and Development Corporation in Pittsburgh, specialising in problems of electromagnetic prospecting for petroleum deposits, In the mid-1930s he was able to follow his inclination to study pure science and attended the Institute for Advanced Study at Princeton University. He received his doctorate in mathematical physics in 1936. His adviser at the Institute was Eugene Wigner, one of the great Hungarian physicists, known for his work in solid-state physics. Bardeen went on to do postdoctoral research at Harvard University, taught at the University of Minnesota, and during World War Il worked with the U.S. Naval Ordnance Laboratory, which took advantage of his earlier work as a geophysicist to develop countermeasures against torpedoes.

After World War 11, U.S. industrial hegemony created the future that belonged to electronics in which innovation and new product development were to play determining roles. This was the context for the development of solid-state physics, the study of the way certain metalloid materials, such as silicon and germanium, conduct electricity. Scientists at Bell Laboratories were hoping to use these “semiconductors” to supplant electron tube technology. Electron or vacuum tubes are circuits in which the electricity can be easily and instantaneously controlled. They were widely used in radio and the emergent computer technologies. But they are big and bulky and have strict limits of practicability. By contrast, semiconductors are many times smaller, more reliable, and cheaper; silicon, for example, is the earth’s second most abundant element.

Although he had considered turning to nuclear physics, Bardeen was recruited in 1945 to solid-state research by Bell. He became, with W. H. Brattain, part of a famous team led by William Shockley. Using crystals of germanium, Bardeen and Brattain in 1948 invented a “point-contact” device which could amplify an audio signal. They showed how it was possible to obtain the same fine control of an electrical current through semiconductors as with vacuum tubes. Resistance could be carefully controlled through “doping” the semiconductor, and a whole range of effects could be demonstrated, including sensitivity to light. These early transistors-as they were named-were fragile, however, and not practical until Shockley developed a more stable version in 1952. The subsequent development of integrated circuits and silicon chips, with all their massive consequences for technology, was based upon this work. It is not surprising that, in 1956, Bardeen shared the Nobel Prize with Shockley and Brattain.

One of the great twentieth-century puzzles in physics had been set in 1911, when the Dutch physicist HEIKE KAMERLINGH ONNES found that at a very low temperature mercury suddenly loses resistance to an electrical current. This was eventually shown to be true of many metals and metallic compounds, although nothing in the laws of physics explained why.

Kamerlingh Onnes correctly surmised that the answer would be found through an application of quantum theory. Forty years passed without progress, however. “John passionately aspired to lead the effort to decipher the mystery of superconductivity,” wrote Bardeen’s colleague, Conyers Herring. To that end Bardeen took a position as professor of physics and engineering at the University of Illinois in 1951. He also may have been motivated to leave Bell Labs because of conflicts with Shockley, who was considered exceptionally difficult to work with.

The BCS theory evolved beginning about 1950, when Bardeen learned that isotopes, or different forms, of certain elements become superconducting at different temperatures. This the vibrations in the atomic lattice through which they move.

After publishing an early, incomplete version of a theory, Bardeen continued to work on it with Leon N. Cooper; a New York scientist-whom Bardeen called “my quantum mechanic from the East”-and a graduate student, John R. Schrieffer. In 1957 they announced a general theory to explain superconductivity.

An elegant theoretical edifice, which NIELS BOHR considered beautiful in its simplicity, the BCS theory shows how superconductivity is a consequence of the relationship between electrons and “phonons,” which are quantums of vibrational energy. Phonons help disrupt the movement of electrons and thereby cause resistance to electrical conduction through a metal.

At low temperatures, however, these vibrations are reduced. This affects the relationship between electrons: They form “pairs” in which two electrons of opposite spin and momentum are united.

(The mathematical analysis of these “Cooper pairs” was worked out by Schrieffer.) When a current is applied, the paired electrons will move through the supercold solid, all with the same momentum and without resistance.

The BCS theory, as it came to be called, was quickly accepted and brought Bardeen, Cooper, and Schrieffer the Nobel Prize for physics in 1972. ( Bardeen thus became the first scientist ever to receive two Nobels in the same field.Superconductivity did not find immediate applicability because of the low temperatures required for it to take place. But finding materials which superconducted at higher temperatures had become a practical goal. In 1986 came the announcement of a ceramic material that became superconductive at 35°K-still cold but getting warmer.

Within a short time other substances had been found which superconduct at about 100°K. This enabled technologists to develop small devices known as SQUIDS (Superconducting Quantum Interference Devices) for applications in medicine, geology, and other fields. The prospect of a usable material at near-room temperature remains a plausible goal. It could lead to profound changes in everyday life.

John Bardeen taught at the Centre for Advanced Study at the University of Illinois from 1959 until his retirement in 1975.

He was quiet and amiable, occasionally lighthearted though capable of considerable anger. He was married to Jane Maxwell, with whom he had two daughters and a son, William, who became an elementary particle theorist. John Bardeen died of heart failure on January 30, 1991.