WHILE Lawrence Livermore's environment of multidisciplinary teamwork has long earned high marks in the research community for nurturing technological advancements, it is now being cited as a basis for a Nobel Prize-by none other than its recipient. Last December, Robert B. Laughlin, a longtime Laboratory employee and a professor of physics at Stanford University, received the 1998 Nobel Prize for physics. Laughlin shared the prize with Horst Stormer of Columbia University and Daniel Tsui of Princeton University.
In 1983 when Laughlin was a member of the Laboratory's condensed matter division, he provided a groundbreaking-and to some, startling-explanation for Stormer and Tsui's discovery of the fractional quantum Hall effect. Laughlin's cogent argument showed that electrons physically confined to two dimensions at very low temperatures and in a powerful magnetic field can condense into a new quantum state with elementary excitations-its "particles"-carrying a fraction of an electron's electrical charge. The explanation, now firmly entrenched as part of quantum physics theory, was considered revolutionary in this context.
Laughlin received the prize in Stockholm from the Swedish Academy of Sciences on December 10. While he is the seventy-first Nobel Prize winner who worked at or conducted research at a Department of Energy institution or whose work was funded by DOE and is the eleventh University of California employee to receive a Nobel Prize in physics, he is the first National Laboratory employee ever to win the prize.
"My presence at Livermore was crucial to my work," says Laughlin. In particular, he gives credit to his Livermore colleagues for aiding him in his intellectual struggle to explain a most peculiar aspect of physics. "My colleagues helped me significantly," he says. "I owe the Laboratory a great deal."





Story Begins in 1879
The story of the 1998 Nobel Prize for physics really begins in 1879, when British physicist Edwin Hall discovered an unexpected phenomenon. He found that if a thin gold plate is placed in a magnetic field at right angles to its surface, electrons will drift sideways compared with the direction of the current's flow. As charge accumulates on one side of the plate, a voltage is created, known as the Hall voltage or Hall effect. As the magnetic field is increased, the Hall voltage increases proportionately as well.
Hall's experiments were conducted at room temperature and with moderate magnetic fields (less than 1 tesla, a basic unit of magnetic strength). In the late 1970s, researchers began to explore the Hall effect at extremely low temperatures (about -272°ree;C, a few degrees above absolute zero) and with very powerful magnetic fields (about 30 tesla). They studied the effect in layered and chemically pure semiconductor devices in which electrons could travel only along a surface, that is, in two dimensions.
In 1980, the German physicist Klaus von Klitzing discovered that the Hall effect under these extreme conditions did not vary continuously as before but jumped in measurable steps. The Hall conductance of these steps was quantized to better than one part in a million to a combination of fundamental constants. Von Klitzing won the Nobel Prize in 1985 for this discovery.
While working at Bell Laboratories in New Jersey in the field of solid-state physics, Laughlin was intrigued by von Klitzing's data. In a notable paper published in 1981, shortly before he arrived at Livermore, Laughlin argued that the experiment was accurate because the quantum Hall effect really measures the charges on electrons (Physical Review Letters B, 23, 5632 [1981]). "Von Klitzing always observed the same proportionality," says Laughlin. "There had to be a simple reason why he got such accurate results. I eventually figured out that the experiment fundamentally measures the charge on the electron, which is, of course, accurately quantized."
The Tsui-Stormer experiments built on von Klitzing's work. In 1982, the researchers used even lower temperatures and more powerful magnetic fields in the study of electron motion in the two-dimensional space at the interface of two semiconductor crystals. The researchers found, to their surprise, additional steps within the steps discovered by von Klitzing. All the new step heights could be expressed with the same constants as earlier but were now divided by different fractions.

Explaining Quarklike Excitations
The new phenomenon was thus named the fractional quantum Hall effect. However, physicists were at a loss to explain the phenomenon. "There were a lot of implausible explanations offered," recalls Livermore theoretical physicist and Laughlin colleague Stephen Libby. "And then Bob came out on his own with a brilliant explanation."
Laughlin had known Tsui and Stormer while at Bell Laboratories, and he was familiar with the unexpected findings coming out of their laboratory. As a new member of the Laboratory's H Division (which focuses on condensed matter physics), he was assigned to modeling extremely hot plasmas. While his security clearance was being processed, colleagues from H Division taught him the mathematics of hot plasmas and how to simulate their interactions on computer.
"I was around researchers who understood fluids," says Laughlin, "and I realized that the fractional quantum Hall ground state had to be a new kind of fluid. There was no other easy way to explain why the experimental findings were so accurate. You had one-third charge `things' in there. It's a great case of truth being stranger than fiction."
Laughlin says he received a lot of valuable physics advice from Livermore physicists such as Forrest Rogers, Marv Ross, and Hugh Dewitt. He also benefited from the generosity of his group leader at the time, Hal Graboske (now associate director for Chemistry and Materials Science at Livermore). Graboske was "very liberal" in allowing Laughlin to research the quantum Hall effect on the side, in addition to his actual job of modeling plasmas.
In 1983, Laughlin offered his groundbreaking theoretical explanation for Tsui and Stormer's findings in a paper published in Physical Review Letters (50, 1395 [1983]). He persuasively showed that electrons in a powerful magnetic field and at extremely low temperature can condense to form a new kind of fluid, the disturbance of which by outside forces causes particlelike motion of the fluid-quasi-particles-to materialize. These carry the precise fractional charges of an electron. These quasi-particles, said the Nobel committee, "are not particles in the normal sense but a result of the common dance of electrons in the quantum fluid."
"The paper was a lightning bolt of clarity. The abstract was one sentence," says Libby, who attended the awards ceremony in Stockholm with his family as the Laughlins' guests. "Bob developed a new kind of wave function, Laughlin's wave function. It's elegant because it's a compact formula that captures all the physics involved." Libby adds, "It's amazing that ordinary, boring electrons in a special situation behave as if they have a fractional charge. Of course, you can't put your hand in and take out a quasi-particle with a fractional charge."






Theory Disturbed Some
While most of the physics community quickly embraced Laughlin's paper, the theory seemed outlandish and even disturbing to a few. "Some people found it easier to dismiss the experiment as being wrong and go on with their lives rather than accept the idea that there was a new kind of liquid exhibiting fractional charges," Laughlin says. Subsequent experiments over the past 15 years have demonstrated more and more fractionally charged steps in the Hall effect, and Laughlin's wave function has explained all of them.
While some experts contend that Laughlin's work will someday lead to revolutionary advances in computers or power-generating devices, Laughlin sees the main value as revealing fundamental insights into nature. "The significance of the discovery is what it tells you about the quantum world. It's cutting-edge knowledge that is completely unexpected. It enlightens us; it's not something you're going to buy, at least not for awhile."
According to Libby, "Bob's work is so important because it's going to affect how we look at many things that may seem disconnected from semiconductors. It pushes the envelope of the possible in quantum mechanics, and thus it will inevitably affect our views of many parts of physics. It enlarges our knowledge of what can exist in the world and that has never failed to have practical effects."
A year after publication of the Physical Review Letters paper, Laughlin won an E. O. Lawrence Award. In 1986, he won the Oliver Buckley Condensed Matter Physics Prize, the nation's most prestigious award in solid-state physics. For many years, he split his time between Stanford and Livermore; he currently spends most of his time at Stanford. His research focus today is high-temperature superconductivity theory, and he has produced a controversial theory on the subject that borrows from his quantum Hall effect research.
Laughlin notes that sometimes scientists have to fight for ideas that they believe in. "All new ideas experience resistance and for good reason. I've had a lot of good ideas that weren't right," he laughs. He expresses concern, however, for younger people who may not want to fight for new ideas because of the possible risk to their careers in times of constrained budgets. In that respect, he is an outspoken advocate for federal support for basic and theoretical research. He decries those who would abandon support for the kind of basic research that makes possible most Nobel Prizes.
"I believe that fundamental research should be one of the main goals of government research because the private sector takes care of other types of research extremely efficiently." In particular, Laughlin urges a rethinking of the role of the national laboratories.
"National laboratories like Livermore are capable of world-class basic research when given the opportunity," he says. "My history proves it."

-Arnie Heller

Key Words: fractional quantum Hall effect, Laughlin's wave function, Nobel Prize, quarks.

For further information contact Robert B. Laughlin (925) 422-7369 (laughlin1@llnl.gov).


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