He's seen as an icon of modern physics, a man whose discovery—at age 26—revolutionized thinking on superconductivity, a phenomenon that some scientists believe may be the most remarkable physical property in the universe.
A crowded New York subway apparently is as good a place as any for brilliant inspiration to strike.
Even a grad student, one still amazed at his good fortune of being daily in the presence of true scientific genius, a major professor who had recently won a Nobel Prize for his fundamental role in inventing the transistor.
But so it was for Robert Schrieffer, a 26-year-old doctoral student of Prof. John Bardeen, a towering figure in what once was called solid state physics. As a researcher with Bell Telephone Laboratories in New Jersey, in 1947 Bardeen had discovered—with W.F. Brattain—the so-called transistor effect. At the University of Illinois at Urbana, Bardeen had built a formidable team of scientific investigators excited by the young field of semiconductor research, from which transistors had sprung. He had hired Schrieffer as a research assistant straight out of the '53 bachelor's program in physics at MIT.
It was a good hire. Nineteen years later, Bardeen would find himself once again in Stockholm, this time to share the greatest prize in science with his former star students and assistants Schrieffer and Leon Cooper. The three men were being honored for developing the Bardeen-Cooper-Schrieffer Theory (forever “BCS” in the annals of science history), the mathematical blueprint that finally explained superconductivity, the curious phenomenon in which electricity flows through a substance without losing any energy—as it commonly does coursing through copper and most anything else. Discovered in 1911 by a Dutch physicist, the phenomenon had defied all attempts to explain the physics behind it for nearly half a century.
The answer had come in a flash to a New York subway rider in January 1957.
“I'd been in New York for a meeting,” Schreiffer recalled, taking his time with a visitor to his office in Tallahassee. Since 1991, Shreiffer has been chief scientist for the National High Magnetic Field Laboratory, coming from U.C. Santa Barbara where he was director of the university's Institute for Theoretical Physics. His training (and subsequent Ph.D.) with Bardeen at Illinois launched a highly decorated teaching and research career that began at the University of Pennsylvania in 1962. He joined Santa Barbara's physics faculty in 1982.
“I suddenly got this idea on the (subway) train, and that evening sat down and wrote out the mathematics for it,” he said. “When I returned to Urbana, I met (Leon) Cooper at the airport and told him how excited I was.”
Today, the BCS theory is considered one of the most sturdy—and useful—tools for explaining a variety of physical phenomena, but primarily those in the branch best known as condensed matter physics. Sometimes still referred to as solid state physics, this is the branch that studies the fundamental science of solids and liquids—essentially everything we humans see, touch or feel. Of all the facets of physics, the field has by far the greatest impact on daily life. Practically every technological advance in industry, for example, hinges on knowledge about the electronic, magnetic or microscopic characteristics of millions of different materials ranging from aluminum to zeolite.
Like a knife, Schrieffer's brilliant subway insight 46 years ago sliced through a knotty conceptual problem that had stymied substantial progress in superconductivity research for four decades. Since its discovery, superconductivity had captivated physicists who were fully aware of what the phenomenon could mean to science and commerce if a practical way could be found to put it to use. Problem was, superconductivity only occurred when materials were super-cold—the 1911 discovery was based on mercury cooled to near absolute zero (minus 459 degrees F). Scientists knew that finding materials that could superconduct—carry electricity without losing energy through heat or light—could save enormous amounts of energy, if an energy-efficient means of cooling those materials to superconducting thresholds could be found. The most logical way to do that, it seemed obvious, was to find materials that superconduct at more reasonable temperatures.
Although mathematically complex, the BCS theory finally gave physicists insight into how to cook up new materials that would do exactly that. Whole new classes of superconducting metals were developed, although by 1973, none had been found that could superconduct much above 23 degrees Kelvin—still a chilly 418 degrees below zero degrees F.
Still, the theory proved useful in other areas of physics—even astrophysics. By 1960, the BCS theory had helped solve a number of complex puzzles in nuclear physics, all having to do with the often odd behaviors of neutrons and protons in the atomic nucleus. Following the 1963 discovery of pulsars—small rotating stars that emit regular bursts of radio waves—astrophysicists were able to use the BCS theory to better understand their bizarre behavior.
But in 1987, the theory appeared to hit a brick wall. That year, scientists working in an IBM lab in Zurich made a startling discovery, unveiling a revolutionary class of so-called “high-temperature” superconductors. This family of copper-oxide compounds (collectively called cuprates) exhibited perfect superconductivity at temperatures above 70 degrees K. It was a stunning breakthrough. Suddenly, scientists could use liquid nitrogen instead of liquid helium as the coolant in superconductivity research. Instead of having to work in a bath of liquid helium (minus 455 degrees F)—a costly and arduous process—scientists could now work with comparatively balmy (minus 320 degrees F) liquid nitrogen, a commodity also much cheaper to produce.
With the dawn of the age of high-temperature superconductors came the realization by physical theorists (Schrieffer among them) that the venerable BCS theory could not easily account for the “new physics” now observed in the high-temperature realm of cuprate superconductors. In fact, the BCS theory had predicted that superconductivity was theoretically impossible above about 40 degrees K. What exactly was nature up to in this brash new class of “hot” superconductors?
This is precisely what Bob Schrieffer—and many other theorists—have been trying to find out ever since '87, when news of the breakthrough set off hoopla rivaling that of the “discovery” of cold fusion two years later. Business Week pronounced the arrival of the new superconductors “more important than the light bulb and the transistor.” It was just a matter of time, boosters claimed, before superconductive devices would be available at room temperature, thereby rendering energy-hogging power stations, transmission lines, computers, and transportation systems quaint oddities of yesteryear.
Fifteen years later, not only has the room-temp revolution failed to arrive, some physicists think it's a scientific holy grail that is so remote that the notion borders on science fiction. Others are more hopeful. Schrieffer and some of his FSU colleagues believe room-temperature superconductivity is within physicists' grasp, and maybe sooner than later. After all, we're already nearly half-way there, says Elbio Dagotto, a friend and colleague of Schrieffer's at the mag lab. A physicist with a background in cuprate research, last year Dagotto was asked by Science to write a status report on the high-temperature race (see “The Race to Beat the Cuprates”, E. Dagotto, Science 293, 2410—2001). He reported that as of September '01, the superconducting record-holder is a cuprate compound that superconducts at 134K. Nominal room temperature—generally considered 72 degrees F—is about 295K. The gap is shrinking, and there are high hopes that a rival class of largely carbon-based compounds, called fullerenes (e.g. “Buckyballs”), may soon surpass the tantalizing progress gained with cuprates.
As a theorist—that breed of scientist that specializes in using math and intuition to deduce how nature does things—these days Schrieffer is less daunted by the hows and whys of high-temperature superconductivity. Admitting he was skeptical when news arrived of the 1986 breakthrough, he said that the intervening years have seen a gradual re-thinking of the BCS theory. Is the brick wall starting to crumble? Schriefffer thinks so. Evidence is mounting, he believes, that the foundation of high-temperature superconductivity may rest on some familiar theoretical groundwork, perhaps a realm of insight that flashed through one highly prepared mind on a New York subway long ago.
John Robert Schrieffer was born in Oak Park, Illinois, arguably Chicago's most famous neighborhood and hometown of several American icons—Ernest Hemingway and (McDonald's mogul) Ray Kroc among them. When he was 16, his dad quit a job as a pharmaceutical salesman and moved the family to Eustis, Florida where he started a successful new career as a citrus grower in 1947. Robert remembers spending most of his Florida days playing with gadgets; first home-made rockets, then ham radio. The latter hobby sparked a career interest in electrical engineering and an invitation to join the freshman class of MIT in 1949. —F.S.