From 1949 to 1984, Anderson was employed by Bell Laboratories in New Jersey, where he worked on a wide variety of problems in condensed matter physics. During this period he developed what is now called Anderson localization and Anderson's theorem ; invented the Anderson Hamiltonian, which describes the site-wise interaction of electrons in a transition metal; proposed symmetry breaking within particle physics ; created the pseudospin approach to the BCS theory of superconductivity; made seminal studies of non-s-wave pairing in the superfluidity of He3, and helped found the area of spin-glasses. He was elected a Fellow of the American Academy of Arts and Sciences in 1963. From 1967 to 1975, Anderson was a professor of theoretical physics at Cambridge University. In 1977 Anderson was awarded the Nobel Prize in Physics for his investigations into the electronic structure of magnetic and disordered systems, which allowed for the development of electronic switching and memory devices in computers. Co-researchers Sir Nevill Francis Mott and John van Vleck shared the award with him. In 1982, he was awarded the National Medal of Science. He retired from Bell Labs in 1984 and was Joseph HenryProfessor Emeritus of Physics at Princeton University. Anderson's writings included Concepts in Solids, Basic Notions of Condensed Matter Physics and The Theory of Superconductivity in the High-Tc Cuprates. Anderson served on the board of advisors of Scientists and Engineers for America, an organization focused on promoting sound science in American government. In response to the discovery of high-temperature superconductors in 1980s, Anderson proposed Resonating valence bond theory to explain the phenomenon. While many found the idea unconvincing, RVB theory proved instrumental in the study of spin liquids. Anderson also made conceptual contributions to the philosophy of science through his explication of emergent phenomena, which became an inspiration for the science of complex systems. In 1972 he wrote an article called "More is Different" in which he emphasized the limitations of reductionism and the existence of hierarchical levels of science, each of which requires its own fundamental principles for advancement. In 1984 he participated in the founding workshops of the Santa Fe Institute, a multidisciplinary research institute dedicated to the science of complex systems. Anderson also co-chaired the institute's 1987 conference on economics with Kenneth Arrow and W. Brian Arthur, and participated in its 2007 workshop on models of emergent behavior in complex systems. A 2006 statistical analysis of scientific research papers by José Soler, comparing the number of references in a paper to the number of citations, declared Anderson to be the "most creative" amongst ten most cited physicists in the world.
