Leo Esaki (born 12.03.1925) is a Japanese physicist and a member of the Japan Academy (1975). He was born in Osaka. He graduated from Tokyo University (1947). In 1946-56 he worked at Kogno Corporation (Kobe), and in 1956 — 60 at Sony Corporation (Tokyo). From 1960 he worked at IBM Corporation.
His main research was in solid-state physics, semiconductor electronics, superconductivity, tunnelling and magnetism. He discovered tunnelling in semiconductors experimentally and in 1957 constructed the tunnel diode (Nobel Prize, 1973). In 1962 he discovered the phenomenon of a strong increase of magnetoresistance at a certain value of the electric field (the Esaki effect), and in 1966 he detected the superconducting energy gap in semiconductors.