Obituary Philip W. Anderson (1923–2020) Nobel winner who transformed condensed-matter and particle physics. hilip Warren Anderson, who has died glasses, a type of random magnet that contains aged 96, led the development of con- both ferromagnetic and antiferromagnetic densed-matter physics. In 1977, he won interactions. Working with Sam Edwards at the a share of the Nobel Prize in Physics for University of Cambridge, UK, he modelled the his discovery of electron localization, glass’s capacity to ‘remember’ the history of its Pwhereby disordered metals become insula- environment. The Edwards–Anderson model tors, and for his pioneering work on mag- was an early forerunner of the neural networks netism. His studies of superconductors led used in modern machine learning. him to propose how the force carriers between Anderson had an artist’s eye for original subatomic particles, such as photons, acquire interpretation, and worked closely with mass: the Anderson–Higgs mechanism is now experimentalists to develop ideas that led to part of the standard model of particle physics. new fields of study. During a year in Japan in Quantum physics’ early triumphs persuaded 1953, visiting the mathematical physicist Ryogo some that advances would derive exclusively Kubo at the University of Tokyo, he became a from reducing nature to its most fundamental master in the ancient game of Go. Just as he particles. Anderson rejected this view, argu- could instinctively see several moves beyond ing that the emergent properties that develop his opponent, he often reached an under- when matter comes together are equally signif- standing of physics that was hard for others icant. He reasoned that, in science, each new to grasp. Unusually intuitive for a theoretical EMILIO SEGRÈ VISUAL ARCHIVES/AM. INST. PHYS./SPL INST. ARCHIVES/AM. VISUAL EMILIO SEGRÈ level of complexity requires new fields, con- physicist, he was able to reduce complex prob- necting physics, chemistry, biology, computer superconductivity. Whereas magnets con- lems so they would succumb to a minimum of science and economics. centrate fields, superconductors expel them, mathematics. Anderson was born in 1923. The son of a plant allowing them to levitate. Following John To the many younger physicists he men- pathologist, he grew up in Urbana–Champaign, Bardeen, Leon Cooper and Robert Schrieffer’s tored, with whom he generously shared Illinois, and developed an early passion for discovery that superconductivity results from inspiring ideas, he was something of a guru. speed skating. At 16, he went to Harvard Uni- electrons forming Cooper pairs, Anderson real- He would invite them, and their families, for versity in Cambridge, Massachusetts, where ized that these pairs are a kind of pseudospin. dinner, developing lasting friendships. He had he fell in love with physics. During the Second In a magnet, fluctuations in the magnetiza- a passion for the outdoors, spending Sundays World War, he worked on radar at the US Naval tion propagate, forming a spin wave. Cooper gardening and clearing the woodland around Research Laboratory in Washington DC. He pairs are charged, and pseudospin waves his house. first learnt about quantum mechanics when cause an electric current that interacts with From 1967 to 1975, Anderson was a visiting a colleague gave him a precious text on it to the electromagnetic fields, which are carried professor at Cambridge, where he was a close repay a wartime loan. Returning to Harvard by photons. When Anderson calculated the associate of Nevill Mott, the third of the 1977 for graduate work, he studied the effects of motion of photons inside a superconductor, Nobel prizewinners. In 1975, he took up a posi- pressure on the broadening of spectral lines, he found that they acquired a mass. tion at Princeton University in New Jersey, mentored by John Hasbrouck Van Vleck, one Anderson realized that there were still- where he devoted much of his research to high- of those with whom he shared the Nobel prize. deeper parallels between superconductivity temperature superconductivity (discovered in In 1949, William Shockley, co-inventor of the and particle physics. In 1962, he proposed a 1986 by Georg Bednorz and Alex Müller). transistor, hired Anderson to join the theory mechanism for subatomic force carriers called Anderson’s resonating valence bond (RVB) group at Bell Telephone Laboratories in Murray gauge bosons to acquire mass in a kind of cos- theory, proposed in 1987, once again bor- Hill, New Jersey. Here, Anderson first focused mic superconductor, now known as the Higgs rows ideas from magnetism, positing that on magnetism. Quantum mechanics predicts field after the British physicist Peter Higgs. high- temperature superconductivity results that electrons carry tiny magnetic moments Anderson’s work was prominently cited in from the injection of charge into an insulating called spin. The attraction of fridge magnets Higgs’s 1964 paper predicting the existence quantum spin liquid. High-temperature super- results when spins orient in the same direc- of the Higgs boson. conductivity has still not been achieved, but tion. By contrast, the read heads of hard disk Work on semiconductors at Bell Labs led many think that RVB theory contains the seeds drives rely on an antiferromagnet, in which the Anderson to propose in 1957 that disorder — of how it might be. Although Anderson has left spin alternates direction on adjacent atomic such as that caused by defects and impurities in us, his ideas are still many moves ahead. layers. By combining the effects of electron a material — localizes electron waves, produc- repulsion and quantum mechanics, Anderson ing an insulator. Today, Anderson localization Piers Coleman is a distinguished professor explained how iron atoms become magnetic, is recognized as a general property of all kinds at the Rutgers Center for Materials Theory, and accounted for the interactions that result of waves in disordered media. But the original Rutgers, the State University of New Jersey. in antiferromagnetism. idea was radical and took two decades and the He was a graduate student with Philip W. In 1958, Anderson discovered a remark- contributions of many leading physicists to be Anderson at Princeton in 1980–1984. able parallel between magnetism and developed in detail. Anderson also studied spin e-mail: [email protected] Nature | Vol 581 | 7 May 2020 | 29 ©2020 Spri nger Nature Li mited. All ri ghts reserved. .