Walter Kohn
American physicist (1923–2016)
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Through England, Adolf Hitler and Jews
Early years in Canada
Kohn arrived in England as part of the Kindertransport rescue operation immediately after the annexation of Austria by Hitler. He was from a Jewish family, and has written, "My feelings towards Austria, my native land, are – and will remain – very painful. They are dominated by my vivid recollections of 1 1/2 years as a Jewish boy under the Nazi regime, and by the subsequent murder of my parents, Salomon and Gittel Kohn, of other relatives and several teachers, during the Holocaust. ... I want to mention that I have a strong Jewish identity and – over the years – have been involved in several Jewish projects, such as the establishment of a strong program of Judaic Studies at the University of California, San Diego.". Kohn also has identified as Deist.
Because he was an Austrian national, he was transferred to Canada in July 1940 after the outbreak of World War II. As a 17-year-old, Kohn traveled as part of a British convoy moving through U-boat-infested waters to Quebec City in Canada; and from there, by train, to a camp in Trois-Rivières. He was at first held in detention in a camp near Sherbrooke, Quebec. This camp, as well as others, provided a small number of educational facilities that Kohn used to the fullest, and he finally succeeded in entering the University of Toronto. As a German national, the future Nobel Laureate in Chemistry was not allowed to enter the chemistry building, so he opted for physics and mathematics.
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Scientific career
Kohn received a war-time bachelor's degree in applied mathematics at the end of his one-year army service, having completed only 2½ out of the 4-year undergraduate program, from the University of Toronto in 1945; he was awarded an M.A. degree in applied mathematics by Toronto in 1946. Kohn was awarded a Ph.D. degree in physics by Harvard University in 1948, where he worked under Julian Schwinger on the three-body scattering problem. At Harvard, he also fell under the influence of J. H. Van Vleck and developed an interest in solid-state physics.
He moved from Harvard to Carnegie Mellon University from 1950 to 1960, after a short stint in Copenhagen as a National Research Council of Canada post-doctoral fellow. At Carnegie Mellon, he did much of his seminal work on multiple-scattering band-structure work, now known as the KKR method. His association with Bell Labs got him involved with semiconductor physics and produced a long and fruitful collaboration with Luttinger (including, for example, development of the Luttinger-Kohn model of semiconductor band structure). In 1960 he moved to the newly founded University of California, San Diego, held a term as the physics department chair, and remained until 1979. It was during this period, he, along with his student Chanchal Kumar Majumdar developed the Kohn–Majumdar theorem related to Fermi gas and its bound and unbound states. He then accepted the founding director's position at the new Institute for Theoretical Physics in Santa Barbara. He took his position as a professor in the Physics Department at the University of California, Santa Barbara in 1984; where he worked until the end of his life.
Kohn made significant contributions to semiconductor physics, which led to his award of the Oliver E. Buckley Prize by the American Physical Society. He was also awarded the Feenburg medal for his contributions to the many-body problem. His work on density functional theory was initiated during a visit to the École Normale Supérieure in Paris, with Pierre Hohenberg, and was prompted by a consideration of alloy theory. The Hohenberg–Kohn theorem was further developed, in collaboration with Lu Jeu Sham, to produce the Kohn-Sham equations. The latter is the standard workhorse of modern materials science, and even used in quantum theories of plasmas. In 2004, a study of all citations to the Physical Review journals from 1893 until 2003, found Kohn to be an author of five of the 100 papers with the "highest citation impact", including the first two.
In 1957, he relinquished his Canadian citizenship and became a naturalized citizen of the United States.
In 1963 Kohn became a Member of the American Academy of Arts and Sciences, a Member of the National Academy of Sciences in 1969, and a member of the American Philosophical Society in 1994. In 2011, he became an honorary member of the Austrian Academy of Sciences (ÖAW). He was also a Member of the International Academy of Quantum Molecular Science.
Death
Kohn died on April 19, 2016, at his home in Santa Barbara, California from jaw cancer, at the age of 93.