Pjotr Leonidovich Kapitsa The Nobel Prize in Physics 1978

biography

Introduction

Scientific progress has become a collective process. No physicist can ever pretend that he has achieved something, that he had had a personal idea or made any original discovery independently of his colleagues. Recognizing this situation does not mean that it is impossible to identify the authors of scientific discoveries, but one should do it carefully. Instead, there is some tendency to attribute discoveries to single persons, an attitude which is not fair enough. Moreover, our prize tradition is certainly very nice, stimulating and generous, but it has some drawbacks: one is tempted to forget those among our colleagues who did not win. With these ideas in mind, I have found particularly interesting to inquire about the history of the discovery of superfluidity

As we shall see, I am not saying that Kapitza in 1978 or Landau in 1962 were awarded the Nobel prize for the discovery of superfluidity, nor criticiz ing this choice. In fact, for Kapitza it was “for his basic inventions and discoveries in the area of low-temperature physics” and for Landau “for his pioneering theories for condensed matter, especially liquid helium”. Further more, in the official presentation speech of Kapitza’s prize, it was mentioned that “The same discovery was made independently by Allen and Misener However, since superfluidity occupies a large part in the official presentation of their prizes, and since nobody else was recognized at that level for the discovery of superfluidity, there is a general tendency to forget that other great scientists have achieved major contributions to this discovery. It is this tendency which I wish to criticize. One example is the article Superfluidity in the Encyclopaedia Britannica, which starts with the sentence: “Super fluidity in helium-4 was discovered in 1938 by the Soviet physicist Pyotr Leonidovich Kapitsa .Another striking example is the presentation speech of the 1996 Nobel prize to Lee, Osheroff, and Richardson, where one reads it was not until the end of the 1930s that PjotrKapitsa (Nobel Prize 1978) discovered experimentally the phenomenon of superfluidity in helium-4” (no mention of Allen and Misener this time). As we shall see below, Landau also considered that superfluidity had been discovered by Kapitza only and he must have had a strong influence on the opinion of his colleagues; for example E.M. Lifshitz wrote:“I have been asked by the editors of Scientific American to give a short survey of what has been learned about superfluid ity, first discovered in 1937 by Peter L. Kapitza at the Institute for Physical Problems in Moscow”.

As for the attribution of the theoretical understand ing of superfluidity to Landau, the situation is more subtle, especially since the discovery of superfluidity in alkali gases

where the existence of Bose Einstein condensation is obvious, but it is somewhat similar. For example R. Donnelly wrote

“Finally, there was no great scientific leader active in understanding liquid helium in the early days. When Kapitza and the great theoretical physicist Landau, followed by physicists such as Fritz London Lars Onsager, Richard Feynman and other greats, came on board, there was a tremendous surge of excitement, which lasted for many years and helped bring the subject to its present state of understanding”. I wish to explain that the contributions by London and by Tisza, which were published three >years before Landau’s, were major breakthroughs in the understanding of superfluidity. Fortunately, my opinion seems to be shared by several other nobr>authors

Some aspects of this issue have already been considered by several au thors, especially by R. Donnelly in the article mentioned above

When trying to go deeper into it, I distinguished three more precise questions 1- Who made the experimental discovery 2- Who has initiated its theoretical understanding ? 3- How did all this happen in a period (the late 1930’s and early 1940’s where the world was torn apart by conflicts and wars One usually considers that superfluidity was discovered in December 1937, the submission date of the two articles on the flow of liquid helium which appeared side by side in Nature on January 8, 1938. On page 74 was the article by P. Kapitza

Pjotr Leonidovich Kapitsa was born in Kronstadt, near Leningrad, on the 9th July 1894, son of Leonid Petrovich Kapitsa, military engineer, and Olga Ieronimovna n?e Stebnitskaia, working in high education and folklore research. Kapitsa began his scientific career in A.F. Ioffe's section of the Electromechanics Department of the Petrograd Polytechnical Institute, completing his studies in 1918. Here, jointly with N.N. Semenov, he proposed a method for determining the magnetic moment of an atom interacting with an inhomogeneous magnetic field. This method was later used in the celebrated Stern-Gerlach experiments.

At the suggestion of A.F. Ioffe in 1921 Kapitsa came to the Cavendish Laboratory to work with Rutherford. In 1923 he made the first experiment in which a cloud chamber was placed in a strong magnetic field, and observed the bending of alfa-particle paths. In 1924 he developed methods for obtaining very strong magnetic fields and produced fields up to 320 kilogauss in a volume of 2 cm3. In 1928 he discovered the linear dependence of resistivity on magnetic field for various metals placed in very strong magnetic fields. In his last years in Cambridge Kapitsa turned to low temperature research. He began with a critical analysis of the methods that existed at the time for obtaining low temperatures and developed a new and original apparatus for the liquefaction of helium based on the adiabatic principle (1934). Kapitsa was a Clerk Maxwell Student of Cambridge University (1923-1926), Assistant Director of Magnetic Research at Cavendish Laboratory (1924-1932), Messel Research Professor of the Royal Society (1930-1934), Director of the Royal Society Mond Laboratory (1930-1934). With R.H. Fowler he was the founder editor of the International Series of Monographs on Physics (Oxford, Clarendon Press).

In 1934 he returned to Moscow where he organized the Institute for Physical Problems at which he continued his research on strong magnetic fields, low temperature physics and cryogenics.

In 1939 he developed a new method for liquefaction of air with a lowpressure cycle using a special high-efficiency expansion turbine. In low temperature physics, Kapitsa began a series of experiments to study the properties of liquid helium that led to discovery of the superfluidity of helium in 1937 and in a series of papers investigated this new state of matter. During the World War II Kapitsa was engaged in applied research on the production and use of oxygen that was produced using his low pressure expansion turbines, and organized and headed the Department of Oxygen Industry attached to the USSR Council of Ministers. Late in the 1940's Kapitsa turned his attention to a totally new range of physical problems. He invented high power microwave generators - planotron and nigotron (1950- 1955) and discovered a new kind of continuous high pressure plasma discharge with electron temperatures over a million K. Kapitsa is director of the Institute for Physical Problems. Since 1957 he is a member of the Presidium of the USSR Academy of Sciences. He was one of the founders of the Moscow Physico-Technical Institute (MFTI), and is now head of the department of low temperature physics and cryogenics of MFTI and chairman of the Coordination Council of this teaching Institute. He is the editor-in-chief of the Journal of Experimental and Theoretical Physics and member of the Soviet National Committee of the Pugwash movement of scientists for peace and disarmament.

He was married in 1927 to Anna Alekseevna Krylova, daughter of Academician A.N. Krylov. They have two sons, Sergei and Andrei.

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