Leonid Veniaminovich Keldysh (born 7.04.1931) is a Soviet theoretical physicist and an academician of the USSR Academy of Sciences (1976, corresponding member 1968). He was born in Moscow. He graduated from Moscow University (1954). He works at the Physical Institute of the USSR Academy of Sciences (as head of a sector); from 1969 he has also been professor and from 1978 head of a department at Moscow University.
His research is in the field of the quantum theory of many-particle systems, solid-state physics, semiconductor physics and quantum radiophysics. He constructed (1957 — 58) a systematic theory of tunnelling phenomena in semiconductors. He was the first to carry out (1957) a correct calculation of the probability of a tunnelling transition that took account of the band structure of the materials used. He predicted the so-called indirect (phonon-assisted) tunnelling effect (1957) and the effect by which the absorption bands in semiconductor crystals are shifted under the influence of an electric field (the Franz — Keldysh effect) (1958). He showed (1964) that the multiquantum photoelectric effect and the high-frequency tunnelling effect are different limiting cases of one and the same process, and he constructed a general theory of these phenomena. In 1974 he was awarded the Lenin Prize for a series of theoretical works on semiconductor physics.
In 1962 he proposed the use of spatially periodic fields (superlattices) to control the electron spectrum and the electronic properties of crystals. He developed (1964) a very general and effective theoretical apparatus for treating strongly non-equilibrium states of quantum-statistical systems. He predicted (1968) the condensation of excitons with the formation of electron-hole drops.
The M. V. Lomonosov Prize (1964) and others.