David M. Lee

David M. Lee, born in 1931, American physicist and Nobel laureate. Lee helped discover that a rare form of helium, known as helium-3, exhibits the phenomenon of superfluidity at extremely low temperatures. In a superfluid state, atoms move together in such a way that the fluid flows with no resistance. A superfluid may climb the walls of a container and may even flow uphill. The discovery made by Lee and his colleagues in the early 1970s launched vigorous investigations into this form of helium and its superfluid properties.

Lee was born in Rye, New York. He earned his bachelor’s degree from Harvard University in 1952 and his master’s degree in 1955 from the University of Connecticut. He obtained his doctoral degree in physics from Yale University in 1959. That same year he joined the physics faculty at Cornell University in Ithaca, New York.

Superfluidity was discovered independently by two scientists in 1937 and in 1938, in a more abundant form of helium known as helium-4. Helium-4 atoms contain one more neutron in their nucleus than helium-3 atoms. For many years afterward, scientists believed that these two forms, or isotopes, of helium were so dissimilar in their atomic structures that helium-3 would not exhibit superfluidity. In the late 1950s, however, physicists developed newer theories that suggested that helium-3 would become a superfluid at a very low temperature. Many labs attempted to achieve this transition, but without success.

Lee began working with helium-3 with a colleague, physicist Robert C. Richardson, and a graduate student, Douglas D. Osheroff. The three scientists were not looking for superfluidity, but were cooling helium-3 to extremely low temperatures—within a few thousandths of a degree of absolute zero (-273.15°C/-459.67°F)—in order to explore the magnetic properties of the isotope.

While working in the lab in 1971, Osheroff noticed indications of pressure changes within the helium-3. He made special note of the changes, believing that they indicated the helium-3 had undergone the transition to a superfluid. The three scientists soon learned that Osheroff was correct, but their results were so unexpected that the scientific community did not accept them until other teams reproduced the results over the next year.

A liquid in the superfluid state does not behave according to the same laws of physics that normal fluids, such as water, obey. Instead, superfluids are subject to the complex statistical rules of quantum mechanics, the branch of physics that predicts how atomic and subatomic particles behave (see Quantum Theory). Superfluids are important to physicists because they offer a macroscopic, or relatively large, system in which scientists can study quantum effects. For their discovery of superfluidity in helium-3, Lee, Richardson, and Osheroff shared the 1996 Nobel Prize in physics.