Anderson, Philip Warren (physicist)

(1923- ) American Theoretical Physicist, Solid State Physicist

Philip Warren Anderson shared the 1977 Nobel Prize in physics with john housbrook van vleck and nevill francis mott for his theoretical work on the behavior of electrons in magnetic, noncrystalline solids.

He was born in Indianapolis on December 13, 1923; shortly afterward, Harry Warren Anderson, his father, became a professor of plant pathology at the University of Illinois in Urbana, where Philip spent his childhood and adolescence. He spent his happiest hours with the families of his parents’ friends, enjoying hiking and camping and developing the political consciousness that would make him an opponent of McCarthyism, a supporter of liberal causes, an opponent of the Vietnam War, and a scientist who refused to engage in classified research. Although the physicists among his father’s friends encouraged him, he initially intended to major in mathematics when he entered Harvard University, in 1940, on a full-support National Scholarship. The world was at war and physics students were urged to concentrate on a field with immediate applications, such as “electronic physics.” After earning his B.A., summa cum laude, in 1943, he spent the next two years doing antenna engineering work at the Harvard Naval Research Laboratories in Washington, D.C.

Returning to Harvard in 1945, he plunged into a series of stimulating courses, including those of julian seymour schwinger. He earned his M.S. in 1947 and that same year married Joyce Gothwaite, who soon presented him with a daughter, Susan. He received his Ph.D. in 1949 from Harvard, after completing his dissertation under Van Vleck, on the pressure broadening of spectral lines in microwave, infrared, and optical spectroscopy. (Pressure broadening refers to the increase in the width of a spectrum line resulting from collisions between atoms and molecules in a gas that occur as the gas pressure increases.)

In 1949, he went to work at Bell Laboratories in Murray Hill, New Jersey, where he joined a stellar theoretical group, which included john bardeen, the coinventor of the transistor. From his Bell colleagues, Anderson learned about fer-romagnetism (the magnetism of substances caused by a domain structure, that is, a material region in which all the atomic magnetic fields point the same way), crystallography, and solid state physics. At the Kyoto International Physics Conference in 1953 he gained a lasting admiration for Japanese culture and met Nevill Mott, whose work he admired.

In the late 1950s, Anderson developed a theory that explained superexchange: the coupling of spins of two magnetic atoms in a crystal through their interaction with a nonmagnetic atom located between them. He was then able to apply the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity to explain the effects of impurities on the properties of superconductors. Working with a French graduate student, Pierre Morel, Anderson studied the Josephson effect, an electrical effect associated with pairs of superconductors. He went on to develop the theoretical treatments of antiferro-magnetics (paramagnetic substances with a small susceptibility to the external magnetic field, which behave as ferromagnetic substances when their temperature is changed), ferro-electrics (crystalline compounds having natural spontaneous electric polarization that can be reversed by the application of an electric field), and superconductors.

During this same period, Anderson did his important work on disordered systems. In crystalline materials, the atoms form regular lattices, which greatly facilitate the theoretical treatment. In disordered materials, the regularity is lacking so that there is no lattice whatsoever, as, for instance, in glass; this makes it very hard to treat such materials theoretically. In 1958, Anderson published a paper in which he showed under what conditions an electron in a disordered system can either move through the system as a whole or be more or less tied to a specific position as a localized electron. Mott drew the attention of solid state physicists to this paper, which became one of the cornerstones in the understanding of the electric conductivity in disordered systems. Anderson would return to the subject of disordered media in the early 1970s, working on low-temperature properties of glass and later studying spin glasses.

In the early 1960s, Anderson developed a model of the interatomic effects that influence the magnetic properties of metals and alloys (now called the Anderson model) to describe the effect of the presence of an impurity atom in a metal. He also devised a method of describing the movements of impurities within crystalline substances, a method now known as Anderson localization. He also studied the relationships among the phenomena of superconductivity, superfluidity, and laser action, all of which involve coherent waves of matter or energy, and predicted the possibility of superfluid states of helium 3, an isotope of helium. On the more practical side he performed research on the semiconducting properties of inexpensive, disordered glassy solids. His studies of these materials indicated the possibility that they could be used in place of the expensive crystalline semiconductors now used in many electronic devices, such as computer memories, electronic switches, and solar energy converters.

In 1967, through the efforts of Mott, Anderson obtained a “permanent visiting professorship” at the Cavendish Laboratories at Cambridge University. For the next eight years he and Joyce divided their time between Cambridge and New Jersey. Anderson headed the Theory of Condensed Matter Group at Cambridge, which he recalls as “eight productive and exciting years, spiced with warm encounters with students, visitors, and associates from literally the four corners of the Earth.”

In 1975, the Cambridge appointment was replaced by a part-time appointment as Joseph Henry Professor of Physics at Princeton University. The following year he became Consulting Director of Research at Bell, and he would later assist arno allan penzias in the difficult years of restructuring that followed the breakup of the Bell Laboratory system. In 1977, Anderson received the Nobel Prize in physics for developing Van Vleck’s ideas about how local magnetic moments can occur in metals, such as silver or copper, that in pure form are not magnetic at all.

The years following the Nobel Prize were productive ones for Anderson. He retired from Bell in 1984 and took up full-time duties at Princeton. During this fertile period he and his colleagues at Princeton revitalized localization theory in solid state physics by developing a scaling theory that made it into a quantitative experimental science.

A longtime proponent of “small science,” in the late 1980s Anderson became a controversial figure in the physics community when he argued before Congress against funding for the proposed superconducting super collider to be built in Texas at a cost of $8 billion. He believed the project would yield neither practical benefits nor any fundamental truths that could not be gained elsewhere and more cheaply. When Congress killed the plan in 1993, Anderson said he was only sorry that Congress had allowed the project to go on for so long. He was also an outspoken critic of “Star Wars,” the Reagan administration plan to build a satellite-based missile defense system.

In 1986, he became deeply involved with the Sante Fe Institute, a new interdisciplinary institution dedicated to emerging scientific syntheses, especially those involving the sciences of complexity. The following year, news of a new class of “high-temperature” superconductors galvanized the world of many-body quantum physics, leading Anderson to reexamine older ideas and search for new ones. He found that he was able to account for most of the wide variety of unexpected anomalies observed in these materials by invoking a new two-dimensional state of matter and a new mechanism for electron pairing called deconfinement.

The amazing range of Anderson’s research in solid state physics has spanned the topics of spectral line broadening, exchange interactions in insulators, the Josephson effect, quantum coherence, superconductors, and nuclear theory. Experimental confirmation continues to support the predictions of Anderson’s theory of high-temperature superconductors, which is expected to find many new scientific applications in the 21st century.

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