Japanese physicist Tomonaga Shin’ichiro won the 1965 Nobel Prize in physics. His work explored the electrodynamic properties of atomic particles.
Shin’ichiro Tomonaga (1906-1979), Japanese physicist and Nobel Prize winner. Tomonaga took an important step for quantum electrodynamics by making mathematical predictions that were consistent with observed physical phenomena of the special theory of relativity. For this work, he shared the 1965 Nobel Prize in physics with American physicists Julian Seymour Schwinger and Richard Phillips Feynman.
Born in Tokyo, Tomonaga became interested in physics after learning about American physicist Albert Einstein's well-publicized visit to Japan in 1922 and reading a book on relativity theory. He earned his B.S. degree in physics from Kyoto Imperial University in 1929. During his final year at Kyoto, Tomonaga studied quantum mechanics without the help of a professor. After graduating, he stayed on at Kyoto as an unpaid research assistant. In 1932 Tomonaga joined fellow researcher Yoshio Nishina at the Institute for Physical and Chemical Research to do theoretical and experimental work in nuclear physics. Tomonaga studied in Germany from 1937 to 1939 with German physicist Werner Heisenberg at the University of Leipzig. He then returned to Japan to obtain his Ph.D. degree in physics (1939) from Tokyo Imperial University (later renamed Tokyo University), where he later became a professor, a position he held until 1970.
During World War II (1939-1945), Tomonaga performed military research for the Japanese Navy and worked on theories of quantum electrodynamics. Earlier work by British physicist Paul Dirac applied quantum mechanics to an analysis of the electromagnetic field. Dirac predicted that particles such as the electron could have an infinite quantity of energy, which led to other predictions that contradicted experimental observations. Tomonaga reworked Dirac's mathematics in the theory so that those infinite quantities no longer appeared. This adjustment made Dirac's theory consistent with observation, and permitted physicists to predict the magnetic and other properties of particles and radiation. The renormalized theory of quantum electrodynamics has proved to be amazingly accurate, even with increasingly sophisticated and sensitive experimental equipment. Schwinger and Feynman also modified Dirac's theory. All three physicists worked independently of each other, but Schwinger and Tomonaga approached the problem in much the same way, while Feynman's method was very different.
After performing his groundbreaking research in quantum electrodynamics, Tomonaga worked in the areas of quantum dynamics, the theory of neutrons, and electromagnetics. He also became increasingly involved in scientific administration, serving as a member, and later president, of the Science Council of Japan in 1951. From 1957 on, he was active in movements against the deployment of nuclear weapons.
Leo Esaki, born in 1925, Japanese physicist whose groundbreaking work on semiconductors earned him a Nobel Prize in 1973. Esaki proved the concept of tunneling in semiconductors and developed the tunnel diode, also known as the Esaki diode. In classical physics, an electric current cannot flow in a circuit interrupted by an insulating barrier—that is, when electrons reach the “wall” of insulating material, they cannot continue forward. Since the 1930s, quantum mechanics, the branch of physics that studies the motion of subatomic particles and related phenomena, had predicted that electrons might be able to “tunnel” through an insulating barrier if it were thin enough. Esaki developed a diode with electrical junctions only 10 billionths of a meter thick through which electrons could tunnel. Esaki shared the Nobel Prize with Norwegian-born American physicist Ivar Giaever and American physicist Brian D. Josephson.
Esaki was born in Osaka, Japan. He attended the University of Tokyo, where he earned a B.S. degree (1946), an M.S. degree (1947), and a Ph.D. degree (1959) in physics. While studying for his doctorate, he worked in Tokyo at Kobe Kogyo Corporation and Sony Corporation. His discovery of tunneling occurred at Sony in 1957 while he was still a student. Esaki moved to the United States in 1960 to join the Thomas J. Watson Research Center at IBM in New York. His research focused on semiconductor physics. He was made an IBM fellow, the company's highest research position, in 1965. He began work in superlattices as part of an effort to demonstrate other predicted but unproven theories of quantum mechanics. Superlattices are synthetic crystals composed of extremely fine layers of different semiconductors. One of the potential uses for this material is in high-speed computers. Esaki stayed at IBM for 33 years, eventually becoming a director of the company. During this period, he also lectured at the University of Pennsylvania and the University of Tokyo. When he retired from IBM in 1993, Esaki returned to Japan. Since then he has served as president of Tsukuba University.
