Julien Bok

Un blog utilisant Blog.espci.fr


Julien Bok  was born on march 14th 1933 in Lodz (Poland); he is married and the father of 2 children. A former student of Ecole Normale Superieure, he obtained the “agregation” in physical sciences in 1956 and the doctorate in sciences in 1959. He was a professor at the University P. and M. Curie in Paris, at ENS and at the Ecole de Physique et Chimie of the City of Paris (ESPCI). He was the director of the Solid State Physics laboratory at ENS and later at ESPCI. His scientific work is mainly on the physics of semiconductors and superconductivity.


1952 passed successfully the entrance examination at Ecole Normale Supérieure(Paris) and Ecole Polytechnique

1952-1956 student at Ecole Normale superieure , Paris (ENS)

1956 Agregation de Physique

1959 Docteur es Sciences,University of Paris, title of the thesis: « Transport properties of charge carriers at high electric field in semiconductors », thesis advisor Pierre Aigrain


In Teaching:

1956-1959 Assistant at ENS

1961-1963 Professor at University of Caen

1963-1967 Professor at University of Paris

1967-1975 Full Professor at University of Paris

1975-2001 Professor « classe exceptionnelle », Professor at ENS and at ESPCI

since 2001 Professor emeritus

In Research:

1959-1961 Military Service. I worked for the French Navy at the Atomic energy Commission on nuclear reactors for submarines.

1961-1963 I started a solid state physics laboratory, working on semiconductors and superconductors at the University of Caen.

1963-1989 I succeeded Pierre Aigrain as head of the Solid State Physics laboratory at ENS, Paris.

The main topics developed in this laboratory were hot electrons, propagation and amplification of electromagnetic waves in solid state plasmas, Josephson effect in superconductors, intercalation compounds of graphite and theory of high Tc superconductors.

1989-2001 Director of the Solid State Physics laboratory at ESPCI

P.G.de Gennes, Director of ESPCI asked me to create this laboratory, in order to coordinate the research on solid state physics in his school by assembling various teams working in different labs. The activity was mainly devoted to the newly discovered high Tc cuprates. The results obtained, in particular in the preparation of thin films by laser ablation led to the creation of joint laboratory with a french company, Thomson-CSF.


1963, 1970, 1983 Visiting scientist, University Of Pensylvania, Philadelphia and Visiting Scientist, IBM laboratory Yorktown, N.Y..

Visiting professor in several foreign universities: Ecole Polytechnique Lausanne, Switzerland; University of Tel Aviv Israel, University of Santiago, Spain.


In France :

1967-1975 Member, then chairman of the solid state section of the French CNRS

1969-1976 Vice president committee on physics of the French Ministry of Science

1972-1975 Member of the “Material Sciences” committee, French Ministry of Science

1981-1984 Member of the scientific council of CNRS


Member, then Secretary of the semiconductor committee of the International Union of Pure and Applied Physics.

Member of the editorial board of: Journal de Physique, Journal of Physics and Chemistry of Solids


Hot electrons in Semiconductors

When a high electric field is applied to a semiconductor, the charge carriers gain energy and become “hot”. This limits the performances of integrated circuits of very small dimensions (fractions of micrometers). I developped simple models to study this effect. We discovered new types of instabilities in semiconductors where electrons and holes are present.

Solid State Plasmas

We discovered new types of instabilities in semiconductors where electrons and holes are present. With Ph.Nozières, we proposed a new kind of solid state microwave amplifier using the properties of “helicon waves” in sold state plasmas. J.Bartelink at Bell labs. has proven experimentally the existence of this effect.

High Temperature Superconducting Cuprates (HTSC)

With Jacques Labbé, we proposed an original model of HTSC based on their bidimensional structure, showing singularities in the density of states as predicted by L. Van Hove. Such singularities have now been seen experimentally by photoemission in all superconducting cuprates. We also proposed to vary the density of carriers by using an electric field and we patented this invention. This model was later developed in collaboration with Jacqueline Bouvier. The main properties of HTSC was calculated as anisotropy of the superconducting gap, specific heat, magnetic susceptibility, Hall effect …..


I spent several months as a scholar visitor in IBM.

I was consultant in several french companies:  Thomson CSF, Saint Gobain, Bull

I was at the origin of the creation of a joint laboratory with ThomsonCSF for the production of superconducting devices in the field of microwaves, agile filters for telecommunications.