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Jain Wins Oliver E. Buckley Condensed Matter Prize

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19 December 2001 -- Jainendra K. Jain, the Erwin W. Mueller Professor of Physics at Penn State, is one of three physicists selected by the American Physical Society to receive the prestigious Oliver E. Buckley Condensed Matter Prize in 2002. He and two of his colleagues, Nicholas Read of Yale University and Robert Willett of Lucent Technologies, will be honored for their theoretical and experimental work in "establishing the composite fermion model for the half-filled Landau level and other quantized Hall systems," according to the society.

Jain is a condensed-matter theorist who is interested in the physics of low-dimensional systems, especially those states in which electrons behave in cooperative ways leading to unexpected behaviors. The major focus of his research has been a quantum fluid obtained when electrons at the interface of two semiconductor materials are cooled to a low temperature and exposed to a strong magnetic field.

"The most surprising feature of this system appears in its transverse resistance, known as the Hall resistance," Jain explains. "In all other systems, as the magnetic field is increased the Hall resistance goes up like a smooth ramp, but here it goes up in steps. Furthermore, the resistance on the flat parts of the steps is spectacularly accurately quantized at certain very simple values, which are characterized either by integers (the integral quantum Hall effect) or fractions (the fractional quantum Hall effect)." The integral and fractional effects, discovered in the early 1980s, were honored by two Nobel Prizes in physics (to K. von Klitzing in 1985 and to R.B. Laughlin, H.L. Stormer, and D.C. Tsui in 1998).

"The integral effects turned out to be easy to explain," Jain says. "In very high magnetic fields the kinetic energy of an electron becomes quantized--a consequence of quantum mechanics -- into levels known as Landau levels, named after a great Russian physicist who first studied this problem several decades ago. The integral effect occurs at magnetic fields when an integral number of Landau levels are fully packed by electrons, with no room to spare. But the fractional effect represents an entirely new, collective state of matter, adding to the previously known collective states like superconductors and superfluids."

To elucidate the physics of the fractional quantum Hall effect, Jain predicted in 1989 the existence of new kinds of particles, which he named "composite fermions," which he says occur when electrons absorb magnetic flux quanta to form new entities. "The fractional Hall systems exhibit absolutely marvelous properties, which are entirely unexpected and inexplicable when you think of them as a collection of electrons, but which become obvious when you think of them as a collection of composite fermions," Jain says. In particular, "the fractional quantum Hall effect is simply understood as the integral quantum Hall effect of composite fermions."

Subsequent theoretical and experimental research by numerous physicists worldwide established the existence of composite fermions, and showed that they not only exhibit the fractional quantum Hall effect, but form many other states. "A beautiful application of the composite-fermion idea was carried out in a theoretical prediction by Bertrand Halperin, Patrick Lee, and Read of a Fermi sea for the half-filled Landau level. This state was later confirmed by Willett," Jain says. "Even though a high magnetic field is necessary for producing composite fermions, at certain values of the field the composite fermions gobble up all the incoming flux of the huge magnetic field so, in effect, they behave as if they do not experience the external magnetic field at all. "That is why they form a Fermi sea, which is something fermions do when they are free from any magnetic field."

The Oliver E. Buckley Prize of the American Physical Society is considered to be one of the most prestigious awards in the field of condensed-matter physics. The prize was endowed in 1952 by AT&T Bell Laboratories, now Lucent Technologies, and is named in honor of an influential president of Bell Labs.

Jain earned his bachelor's degree from Rajasthan University in India in 1979, his master's degree from the Indian Institute of Technology in 1981, and his doctoral degree from the State University of New York (SUNY) at Stony Brook in 1985. Jain was a postdoctoral research associate at the University of Maryland from 1986 to 1988 and an associate research scientist at Yale University from 1988 to 1989. He joined SUNY at Stony Brook as an assistant professor in 1989, was promoted to associate professor in 1993, and to professor in 1997. He joined Penn State in the fall of 1998 as Penn State's first Erwin W. Mueller Professor of Physics.

[ B K K / J K J ]

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