In 1972 John Bardeen did something that no other physicist, not even Albert Einstein, had ever done. He won his second Nobel Prize in physics. The first was awarded to him (and to Walter H. Brattain and William Shockley) in 1956 for "investigations on semiconductors and the discovery of the transistor effect."
Their pioneering efforts ushered in the age of modern electronics and the integrated circuit, which eventually spawned the computer chip and the cell phone. Arguably, the transistor (and all of the devices it has made possible) is the single most important invention of this modern age and ranks with fire for its effects upon society and civilization.
Bardeen (along with Leon Neil Cooper and John Robert Schrieffer) won a second Nobel Prize in 1972 for "their jointly developed theory of super-conductivity," usually called (using the last initials of the three scientists) the BCS theory. In essence, BCS theory explains the phenomenon of superconductivity in Type I superconductors— metals , such as mercury, lead, and niobium.
According to BCS theory, at extremely low temperatures the lattice structures in these metals are very well-ordered and have little intrinsic vibrational motion. As an atom in a Type I superconductor gives up electrons to the Fermi conduction levels , it becomes a positively charged point in a sea of electrons. Below the critical temperature (the temperature at which a metal becomes superconducting), electrons in this Fermi level interact with the lattice atoms, producing vibrational motion that, in turn, interacts with a second electron. The result is the passage of electrons in the metal as "Cooper pairs," which move through the metal with zero resistance. Although Type I superconductors have not found extensive use because of their extremely low critical temperatures, the Type II or "alloy based" superconductors have radically changed science and technology, as they have enabled the construction of superconducting magnets, used in a range of devices, including magnetic resonance imaging (MRI) devices.
Brown, L. M.; Pais, A.; and Pippard, B., eds. (1995). Twentieth Century Physics. New York: American Institute of Physics Press.
Serafini, Anthony (1993). Legends in Their Own Time. New York: Plenum Press.
Flatow, Ira. Corporation for Public Broadcasting. "Transistorized!" Available from http://www.pbs.org/transistorized .
Godfrey, Stephen. Carleton University Department of Physics. "Superconductors: BCS Theory, Josephson Junctions, SQUIDS, etc." Available from http://www.physics.carleton.ca/courses/ .
Nobel e-Museum. "John Bardeen—Biography." Available from http://www.nobel.se .