David M. Lee
Born: 20 January 1931, Rye, NY, USA
Affiliation at the time of the award: Cornell University, Ithaca, NY, USA
Prize motivation: "for their discovery of superfluidity in helium-3"
Prize share: 1/3
When certain substances are cooled to extremely low temperatures, they become superfluid, flowing without any friction. This applies to helium-4, the most common form of helium, but for a long time the superfluidity of helium-3 was in dispute. The different types of helium are described by different quantum mechanical rules and equations under which helium-4 has a whole-number spin while helium-3 has a half-number spin. In 1972 David Lee, Douglas Osheroff, and Robert Richardson verified that helium-3 also becomes superfluid at extremely low temperatures.