And Daniel Tsui makes 70: Another Nobel Prize in physics

Add Daniel Tsui, SM'63, PhD'67, to the list of Nobel laureates affiliated with the University of Chicago. This fall, the alumnus received the 1998 Nobel Prize in physics, making him number 70. Tsui, the Arthur LeGrand Doty professor of electrical engineering at Princeton University, shared the prize with Stanford professor Robert B. Laughlin and Columbia professor Horst L. Störmer "for their discovery of a new form of quantum fluid with fractionally charged excitations."

The three found that electrons, when subjected to a powerful magnetic field, can condense and create a quantum fluid, work that has led the way for other discoveries about the inner structure and dynamics of matter.

Tsui and Störmer made the discovery at Bell Laboratories in 1982. Creating a trap with two semiconductor wafers, they kept the electrons in a plane, moving only in two dimensions. Then, after applying extremely powerful magnetic fields and very low temperatures, they measured the Hall resistance, and observed that the electrons acted as though they had fractional charges. Because it's impossible for electrons to have fractional charges, they began searching for an explanation. Within a year, Laughlin had come up with one: The magnetic field created "holes," or vortices, in the "sheet" of electrons. As the electrons sought to fill those vortices, they created a quantum liquid with fractional quantum numbers and nearly resistanceless flow. The phenomenon is known as the fractional quantum Hall effect.

"It's an interesting and rather exotic development that opened an entirely new field and created many interesting and important questions in physics," says Woowon Kang, a U of C assistant professor in physics who collaborates with Störmer. "It has stimulated many theoretical and experimental breakthroughs applicable to other fields in physics." In particular, the work could offer insights into high-temperature superconductivity and the quantum fluids that occur in superconductors.

Tsui studied quantum fluids while at the U of C, doing his Ph.D. research on a superfluid formed by cooling helium gas to just a fraction of a degree above absolute zero—minus 459 degrees Fahrenheit. After receiving his doctorate, Tsui was a research associate at Chicago for a year, then worked at Bell Laboratories from 1968 until 1982, when he joined the Princeton faculty. A member of the National Academy of Science and a fellow of the American Physical Society, Tsui—along with Störmer and Laughlin—had a precursor of the Nobel this past April when the trio won the 1998 Benjamin Franklin Medal in physics for the same work.—K.S.