Interview with Alexander Voronel, part II

II. Critical phenomena

SSS

So in 1955, 1956, you get a job in what is the equivalent of the National Bureau of Standards.

AV

Yes, I never left this Institute, until I came here. I worked first on calorimetry, because the specific feature of this Institute was performing exact measurement. So we had to improve the accuracy of whatever had been done previously. But to improve the accuracy, the best way is to make the investigation. It is necessary, you know. So I did it. You know, I had been interested in critical phenomena from my university years. But at that time, I was too young in physics and too ambitious, for I thought that I could build the whole theory of liquids. At that time, Landau -- and all of us were all under some influence of Landau's ideas -- and Kharkov University, in particular, is a scientific school, which remained a satellite of Landau's school. So Landau had claimed that it's impossible to have a theory of liquids, because in solids, there is some universality because they are rigid; gases have some universality because at low density and temperature, molecular encounters are rare -- the mean free path is large compared to the range of the intermolecular force. But in liquids, both interactions, molecular movement and thermal motion are roughly of the same order, so there couldn't be some universality there.

SSS

And at that stage -- your notes show things like Boltzmann equations -- and I assume that these descriptions, classical descriptions of liquids is something you're familiar with.

AV

Yes, but you know, this equation doesn't work for liquids, so this is the problem. So Landau was right in some broad sense. But in particular, it was not right.

SSS

Because you have, so to say, a universal equation for the motion of liquids which only involves viscosity and density, that's some kind of universality, right?

AV

Yes, and this was known to him, and he didn't deny this. But a theory of liquid which is a microscopic one, that he denied. And we were under this influence on one side, but from another side, from my own experience, I saw a universal features in liquids, and that's why I was sure that he's not right in particular.

SSS

Can you say a few words about what you understood about universality in terms of gases and solids?

AV

OK, universality of gases is based on the fact that particles are so far one from another that the interaction doesn't play much role. So you can neglect it, or if you are not neglecting, you can use the first approximation with some correction. This correction is small...

SSS

Universality means that you have similar equations describing all gases, and for solids?

AV

And for the solids, the opposite is true, the interaction is so strong that solids can be investigated as rigid structures, structures that have some universal features like waves propagation in them, or obey some Hooke's Law, or laws describing elasticity and so on, so we also have the universality.

SSS

(unclear)

AV

Yes, but for liquid it's not obvious. And so Landau said, no theory of liquids, but actually, empirically, I got the impression that we had some universality. I had no idea what they are, where this universality comes from, and so on. But I was sure that I had to look for it. So even in my diploma work, I put some stress on trying to find some universal features, and some similarities between different liquids, and I was sure that for that we have to investigate, some simple liquids. For the solid state, we have to investigate not complicated crystals, but the most simple, and the same should be true for liquids. We have to investigate something simple. And that's why I was involved in this argon investigation and so on. And then, when I investigated liquids, it was natural to see these liquids in the whole range of existence of the system, from the critical to the melting point. So, since investigating the critical point was more difficult...

SSS

You looked at the...?

AV

I looked just looked at the difficult side, and what I found is that the experimental data was very, how to say, dirty, and the closer to the critical point, the data is scattering more and more, so I had to assume from the very beginning that probably the very approach was wrong.

SSS

When you say "investigated," what were you measuring at the critical point?

AV

I was measuring first the heat capacity, then I was measuring also the form of the co-existence curve, the density-temperature relations. And it was an interesting thing that in spite of the shape that the Landau theory predicts, -- the parabolic shape -- the empirical fact was that it was degree 1/3, instead of one half. And the interesting thing was how Landau explained this. He said, "OK, well, the theory requires that we are rather close to the critical point. But we are never close, so the closer, it will be possible to get more close" And the interesting thing is, that if you are too close, let me write it down, like this, you know? If you are not too close then you are talking about closeness, vicinity of the critical point, the accuracy of your approximation or heating depends on the range, and if this is the range, let us say, very, very narrow, then any error in T_c can provide you any form you wish to test. So you have to be far enough from this point to neglect this error, that's why his argument never could be rejected, because he says, "OK, you are not close enough." OK, so this was the argument of that time.

SSS

How much contact did you have with Landau? You actually went to talk to Landau?

AV

No, about that, no. Let me be more precise. I was in contact with Landau, but not on this issue. Because my close friend, Professor Azbel, was his close pupil, that's why. I could always discuss things with Azbel, and Landau would discuss it with him. I met with Landau as a friend of Azbel, yes. But who was the person I discussed theoretical issues with? It was Evgeny Lifshitz, who was the co-author of Landau's Course, so I could trust him.

SSS

Are we now talking 1958,1959, 1960?

AV

Yes, let me see... I was interested, particularly interested in these problems in the mid-fifties, 1956, 1957, and then it was the very impressive work published by Fairbank on the lambda point of helium. He found that there is a singularity at the lambda point of Helium. Since I already suspected that also at the critical point there is a singularity, Fairbank's article made a great impact on me. And I cannot be sure now that I had formulated very concisely the notion of a singularity at the critical point before Fairbank. I cannot remember now, and it's not so important for me, but I was really impressed by this work, and I wanted to investigate this at the critical point. What I do remember now, even before I saw Fairbank's article, is that in the measurement of the heat capacity near the critical point, the scattering is becoming more and more disordered when we are getting closer and closer to the point, I did realize that something is wrong with the technique and the understanding of the point. This I am sure about. But whether I did realize that this is a singularity, that this is an infinite value, this I don't remember, but at least, after that I was absolutely sure. Because I was sure that the lambda point and the critical point are the same kind of problem.

By the way, Landau denied it, because he expected in both cases that the final values of the heat capacity would have some jump, but he didn't expect any singularities. Also, he didn't make a connection between these two phenomena. Now it's almost obvious. Why didn't he at that time? I cannot answer this question, because at that time when I investigated it, I was almost sure that they were the same. One of the reasons, which may be a little funny, but might be relevant in Russia, is that Landau was not 100 percent loyal, so he was sometimes, how to say it, playing a different role, of not being a real Soviet patriot and so on. So he was chased from Moscow University, this you do know, yes? And he was kicked out from the university because of the activities of a group of scientists, who were not good scientists, but still they were qualified and adequate. One of them was Semenchenko,-- you probably don't know this name -- and this Semenchenko proclaimed that critical phenomena and second order transitions are the same. And since Semenchenko was anti-Semitic, and anti-Landau, and was the most active in the kicking out of Landau, probably one of the reasons why Landau never mentioned this analogy was because of this. Actually, it is not an analogy, it is really the same.

SSS

The fact that you read Fairbank, does that imply that you were getting the Physical Review regularly?

AV

Yes, more or less regularly, yes, regularly, yes.

SSS

And you would look through it carefully?

AV

Oh, yes, very thoroughly and carefully. You know, I do remember one thing about how I felt. Some people when they find in the literature something they had guessed, they are upset, because it does mean that someone had intimated it before them. But because I was so young, it was the opposite with me: I was delighted that Fairbank had done it, for it meant that I had guessed right. I had had an insight about one of the characteristics that is typical of the critical point, that at the critical point, the time of relaxation is much longer than in other states, and near the critical point this is becoming crucial. This was one of the reasons why people couldn't investigate the critical point reasonably well, because they didn't expect this time to become macroscopic. But Fairbank also had recognized that, even in helium. So I was delighted. I had recognized this before. So when I read it in his paper, I was delighted.

SSS

Fairbank's paper was important?

AV

Oh, yes, it was very important, and so after that, I always could justify my work, because in Russia you have to justify your work. So I could justify my investigations with Fairbank. I do remember that my colleagues who were theoreticians and who worked under the influence of Landau told me, "be cautious, because if Landau says you are a pathological person..." -- You know, in Landau's terminology, the physicist who is doing something wrong is a "pathologist". So if he says that you are a pathologist, it will be the end of your career. But since I did not work in an academic institution, and I was independent, I was absolutely out of this. So I sought advice only when I wanted it, not when they wanted. When then I investigated this point, and I do remember that it was in 1962, or 1961, when I first was really convinced that I had a singularity, I called Mark Azbel in Kharkov, because he was in Kharkov at the time, I told him, "Mark, you know, I found it," and he was one of those who supported me. And then I called Evgeny Lifshitz, and also told him, in 1962.

SSS

Can you say a little bit more about conditions in the laboratory? You had your own lab?

AV

Yes, this is also interesting. I was accepted to this laboratory not by chance, not because they were so open, but because they really lacked people. This institution was located in Moscow, but by the general plan, they moved from Moscow to about 40 kilometers from Moscow to this special, rural area. They knew that all the researchers were leaving, so they had to seek and accept new ones. And they accepted me because of that, and the result was I was rather independent from the very beginning. And my boss at that time was Professor Strelkov. Maybe you heard of him? Professor Strelkov. This is an interesting story, if you are interested in stories, in history. Professor Strelkov worked as a technician for Professor Kapitza in the 1930's.

SSS

After Kapitza comes back to Russia.

AV

To Russia, yes, this was at the very end of the 1930's. The interesting thing is, and this is gossip, but gossip is part of the history. The gossip is that really it was he who discovered superfluidity. But he didn't understand anything. So he showed Kapitza the data, and said to him, "I don't understand why, what does it mean?" And Kapitza told him what to do, and how to investigate the phenomenon, and so the first experiments on superfluidity were those of Strelkov's. He was not a great scientist, and he was rather modest, rather modest, and he was very nice gentleman, and a very pleasant one. But still he was a professor , and so he understood his role as the protector, the shield for young scientists. He helped me only in one sense. He provided the favorable conditions for the work. So that's why I liked him very much, and he was really a good force for me. And then, when the institute left Moscow to this new site, all the Moscow people left the institute. I was alone and the administration had no other choice but to appoint me chief of the laboratory. At that time, I was chief of my own laboratory.

SSS

And this is 1960 when you become chief of the laboratory?

AV

Yes, 1960. I was 29 and became the youngest chief of a lab. And I do remember that my position in my institute was not very strong. You understand, first of all that I was young; then I was Jewish. And I do remember that in 1962 or 1963, I don't remember exactly when, there was a visit by a scientist from the National Bureau of Standards -- I now don't remember the name of the particular scientist. This was the time of detente, so they came.

SSS

Was it Ambler, or any of the people in his laboratory?

AV

It seems to me, that he was in an analogous position as the director of my Institute. In Russia the director is accepted as the big boss. So when a very distinguished visitor came, our director accompanied him from laboratory to laboratory, and told him what people are doing. So they came into my laboratory, and my boss said "This is the calorimetry laboratory." and asked, "What are you doing?" I said, "I am doing this and this, and this and this...." And the guest asked: "What is your name?" I said Voronel. (very loudly) "You are the same Voronel?", he said. And this, "You are the same Voronel," changed my position in my institute. Because after that, the director said, "Oh, you are the same Voronel." Before he didn't take notice what I'm doing, it was not interesting for him at all.

SSS

Just an aside: did you move from Moscow to be closer to the institute, or did you commute every day to it?

AV

No, no, I had no flat in Moscow. So it was good for me that they moved, because as a result they gave me a flat.

SSS

Did your wife have a flat in Moscow?

AV

No, no.

SSS

Nobody had a flat. So you lived close to the Institute?

AV

So we lived 40 kilometers from Moscow all the time.

SSS

And that's where your son grows up?

AV

Yes. OK, so after that, I got some letters from abroad about that, and I really was able, I could explain why my work is so important. After that, after the real interest of Michael Fisher, I got a letter from him. Actually I didn't get at all the first letter from Michael Fisher to me. I don't know what happened. Then I was summoned to some committee, some scientific constellation of some sort, I don't know. Actually it was the KGB, as I could guess, and they asked me "Why is Fisher writing to you all the time?" I said, "I don't know, is he writing to me?" They said, "Here is the letter. Read it." And I read it, and was his third letter to me. And I had wondered why Michael isn't answering me, and I had suspected that he doesn't get my letters. So when answering, because I knew the Russian pathology, I didn't answer that he needs to have my data, no, I answered: "We are in the same field, and I believe that he needs me as much as I need him. I need some data from him, to be successful." They then said "Uh huh. And which science will gain more from that, Soviet science, or English science?" I said "Of course, Soviet." "OK", they said, "we shall consider whether you can write to him or not." But the main thing for me was just to read that letter. After I read his letter, I did a trick, I published a paper. What he had asked me in his letter, what he had wanted was my numerical data. But usually the journal doesn't publish numerical data, you know. So, how could I send him numerical data? I went to Evgeny Lifshitz, and explained to him the problem, and he agreed to make an exception and to publish the numerical data in the paper. And there in it, at the very end, to make it very clear, I wrote that I'm grateful to Michael Fisher. But you know, this is a name which could be Russian. Michael Fisher could be also Russian, so it's not clear.

SSS

And this paper is published where?

AV

It was in JETP, the Journal of Experimental and Theoretical Physics.

SSS

1962.

AV

This was 1963, or 1964, I don't remember when. Fisher till now shows this figure.

SSS

Publication in 1962?

AV

Yes, you know [of it].

SSS

The question was, where did your stimulation come from?

AV

You know, I had read the paper of Domb and Fisher, when Fisher probably was a student of Domb, yes, I read that publication. I read that original paper at that time in the 1960's, this I did. But the main issue was that it was not, absolutely not clear, whether these calculations were relevant or not to reality. That's why it was a interesting guess for me, not more than that, you know, so that's why the real impact for me was the book of (unclear). And it was, even, very challenging, to see whether it's really true. But the main stimulus to me was from that work.

SSS

At the institute where you worked, how much low-temperature work was going on, at your Bureau of Standards?

AV

It had a special department, which looked after the thermodynamic thermometer, because the temperature scale (unclear). It also was involved in the production, calibration, and graduation of platinum thermometers. And also some low-temperature measurements. What kind of measurements? This was somewhat unclear. They kept us for the fulfillment of their activities. Of course, we had to prove our high-quality performance, and that's why we got to publish the works where accuracy was important. But actually they didn't watch our work carefully. But my measurements after I came in 1956, I made measurements not only of critical points, but also of magnetic Curie points, and also of suceptibilities of magnetic materials. But the most attractive results were from measurements at the critical point because I had found a way to approach closer to the point than all the other investigators. So as a result my singularity was placed much closer and the same I showed that also this cubic form of the parabola is kept closed (unclear) and is...

SSS

And you're own work was such that you could immediately see that what Fairbank was doing was accurate. That you could trust it? That you didn't need to go to Kapitza's Institute to collaborate?

AV

To check it out.

SSS

Oh, right, right. And, from what I gather in terms of what you do, you do it on your own in the laboratory. If you need theoretical input and criticism, you visit Azbel and Lifshitz.

AV

Yes, I got by, but actually, they were not people who were working in this particular field. In my particular field, they were people whose names you probably know: A. Larkin, he is in the United States now. Then, Pokrovsky, and the third one, probably you don't know A. Dykhne and V. Vaks --- they are both in Russia.

SSS

And how much contact do you have with these people?

AV

In the early 1960's not very much, because I was absolutely separated from everybody. I only had a friendship with Mark Azbel because we had been friends when attending the same university, so we were friends from before. This was for me enough because I didn't need at the time much theory, and I had read Domb and Fisher. Then the work of Yang was published, which interpreted my work. And this gave me publicity. All the theoreticians came to me, and they wanted to make a sort of boom around things. It was a little revolution, a microrevolution, in this small circle. Because before that, pupils of Landau, for example, Gor'kov asked me "What are you doing?" I said "I am doing critical point investigations." He says "Is there something unclear about critical points?" I said, "Yes, there is much, I think, that is unclear." He said "Oh, are you sure?" and I said "Yes." And he said, "But Landau is doubtful." And I said "So what, Landau is doubtful." And this was like that. Those who worked in other fields were interested. You know, this is interesting. And that Landau's pupils couldn't really pay attention because of Landau, yes. This is interesting, too.

SSS

And did Yang write to you at the time?

AV

No, he didn't write to me, but he published. And so as a result, we made a few symposiums together.

SSS

This was about the late sixties?

AV

This was the late 1960's, yes, and then again I got into trouble. You know, I was lucky with trouble with the Soviet regime. In 1966 Sinyavsky and Daniel -- maybe you remember these names, they are not scientific names, they are two writers, who published their book abroad -- were my personal friends, not exactly mine, but my wife's, because my wife was in literature, and so they were friends and also mine. And from that time on, the KGB was looking after me and after Azbel. Azbel was also involved, and we were, in some troubles. And my institute had to punish me just to show their loyalty to the government. So they dismissed me from the supervising of my laboratory. And then during the next two or three years, they couldn't find anyone who agreed to accept the post after me, because it was indecent you know, and they didn't know what to do. Until I told them, appoint my pupil, Anisimov. He is now in America and works in Maryland, so he's in contact with Fisher. It was clear that if they appoint him it's better for me -- and they can discuss every question with him. So they did this. But still they wanted to oppress me in other ways to show their loyalty. When I applied for a visa to emmigrate abroad and the KGB gave me a visa, they summoned me and told me, "OK, now, we have to be frank. There is something wrong between us. Can you explain why you wanted to emmigrate?" I indicated that it should be obvious. "Even if you are not talking about some other thing, you know how I was persecuted." And they said, "You know, Professor Voronel, you have to complain to us. And we will punish them for being so rude to you! I said, "I didn't know." And they said, "This proves you are not really, not truly a Soviet citizen. Because a good Soviet citizen goes to the KGB."

Return to Part I of this interview.