Superconducting materials can carry an electrical current with no resistance or loss of energy. Two main classes of superconductors exist. So-called type I superconductors can repel a magnetic field but lose their superconductivity if the field exceeds a certain limit; a theory explaining how they work won the 1972 Nobel Prize in Physics. Type II superconductors, in contrast, retain their superconductive properties even in intense magnetic fields. This year's prize recognizes the theories Ginzberg (above, center), of Moscow's Institute for Physical Problems, and Abrikosov, now at Argonne National Laboratory (above, left), formulated to explain how these type II materials work. Although these ideas were first put forth in the 1950s, the committee notes that "they have gained renewed importance in the rapid development of materials with completely new properties."
The third portion of the 10 million Swedish kronor prize went to the University of Illinois's Leggett (above, right) for a theory proposed nearly 30 years ago to explain superfluidity, the ability of a fluid to flow without losing energy through friction. The superfluidity of helium, which occurs at 2.7 kelvins, was first observed in 1938. In the 1960s, scientists demonstrated the phenomenon in a rare isotope of helium with two protons and one neutron (3He) at temperatures 1,000 times lower, a feat that won the 1996 physics Nobel. Leggett was honored this year for his description of how 3He atoms interact in the superfluid state. According to the committee, Leggett's theory has also proved useful in other fields, such as particle physics and cosmology.