Their names are in the history of the Institute

Continuing the dialogue with Nikolay Maksimilianovich

On 6 June, a seminar in memory of Professor N.M.Plakida was held in the Blokhintsev auditorium of BLTP. The Seminar brought together employees of BLTP, FLNP and MLIT.

Viktor Aksenov

The event was opened by the chief researcher of FLNP V.L.Aksenov that explained that the Seminar was held by two laboratories of the Institute - BLTP and FLNP, since Nikolay Maksimilianovich's scientific activity referred to both. In his report "N.M.Plakida - scientist and teacher" Viktor Lazarevich briefly touched upon the scientific biography of N.M.Plakida. In 1954-1960 he studied at the Department of Theoretical Physics of N.N.Bogolyubov at Moscow State University. As a postgraduate student he began working in the Department of Nuclear Theory of FLNP under V.G.Solovev, but after his postgraduate studies he returned to the department, where he worked as an assistant. Since January 1966, Nikolay Maksimilianovich has become an employee of the statistical mechanics sector that was organized at FLNP under the supervision of S.V.Tyablikov. While still a student, in 1959, Nikolay published his first scientific paper, "The spectrum of elementary excitations of a non-ideal bose gas," in the "Reports of the USSR Academy of Sciences." Nikolay Maximilianovich was not only a graduate of N.N.Bogolyubov's school, but also his student. Nikolay Nikolaevich distinguished between these two concepts: he considered his students to be those who he published at least one joint paper with.

"Nikolay Maximilianovich worked on many scientific problems, but in the scientific world he is widely known for two main results - theories of anharmonic crystals and superconductivity," Viktor Lazarevich emphasized. The speaker also contributed to the construction of the anharmonic prototype together with Bogolyubov and Plakida. In 1966, work started on the IBR-2 project and a couple of years later, the discussion turned to developing a scientific programme for the reactor. "In V.G.Solovev's department, where we worked at the time, an annual report was held, at which each employee had to report on what he had done that year for IBR-2," V.L.Aksenov recalled. The cooperation between BLTP and FLNP continued that we saw with our own eyes - photographs of theorists' visits to the experimental facilities of FLNP that were being developed and operating were shown at the seminar.

The discovery of high-temperature superconductivity (HTSC) in 1986 caused an explosion of activity among theorists. Viktor Lazarevich said that N.M.Plakida that began scientific research with superconductivity said that his time had come. Many basic concepts of the theory were laid down by N.N.Bogolyubov in his fundamental papers on statistical mechanics and superconductivity. "Our joint articles with Nikolay Nikolaevich and N.M.Plakida in 1988-1990," V.L.Aksenov noted, "were based on these papers with the addition of the mechanism of structural instability."

The next stage began after a compound was synthesized in 1993 in the laboratory of E.V.Antipov that was participating in the seminar, at Moscow State University that allowed the temperature of high-temperature superconductors to be raised to 150K. Research into the structural features of new superconductors began at IBR-2. Nikolay Maksimilianovich immersed himself entirely in this research that ended in success. V.L.Aksenov introduced to the audience Plakida's theory - the kinematic spin-fluctuation mechanism of high-temperature superconductors in systems with strong electron correlation.

The speaker described the pedagogical talent of his teacher as follows: "We traveled quite a lot - to conferences, schools and he was always eager to tell someone something. And the amazing thing is that people - not students, but professors - listened to him with bated breath; at any school he was followed by a tail of people wanting to gain knowledge. He was an outstanding teacher."

Viktor Yushankhay

In his report "Continuing the dialogue with the teacher", V.Yu.Yushankhay (BLTP) shared some of his memories of his long-term collaboration with one of his teachers, N.M.Plakida. This long-term collaboration began in 1987, when the speaker was invited to work in N.M.Plakida's sector, several months after the discovery of HTSC. During the many years of collaboration, Nikolay Maksimilianovich demonstrated an unobtrusive, respectful style of communication, while leaving complete freedom in the choice of tasks. "I would like to start with a story told to me by my teacher, about one of his meetings with Dmitry Blokhintsev. It was in the late 1960s, when ultracold neutrons were discovered at FLNP and the effect of anomalous heating of ultracold neutrons arose. D.I.Blokhintsev invited N.M.Plakida to his place, told him about the problem, took out paper and a pen and said: now, let's formulate the prototype and start the calculations. This story was filled with admiration and confidence in his knowledge. The story itself had a long continuation, since the final solution was not found immediately. After that, I realized that my first meeting with Plakida was in many ways similar to this story. When I came to him in 1987, my knowledge base was small. Nevertheless, Nikolay Maximilianovich proposed a problem and a solution method, we performed the first calculations together and then our communication mode moved to rare meetings to exchange opinions. I have collected several slides, since it seems to me that the issue that we discussed with Plakida in the early 1990s has recently received an unexpected development. It turned out that this issue can be studied by analog quantum computers, that is, a more complex quantum system can be studied by a simpler quantum system. And Viktor Yurevich concluded his report as follows: "In my thoughts today, I turn to our communication with Plakida 30 years ago and continue the dialogue with him."

Anatoly Balagurov

In his report "Crystals, alloys and neutron diffraction: theorists and experimenters together" A.M.Balagurov recalled several episodes of cooperation with Nikolay Maximilianovich, his direct participation in the discussion of the results of experiments on IBR-2. He began with photographs of theorists' visits, including N.M.Plakida, to the reactor and recalled their active participation in laboratory seminars. In 1982, superprotonics were discovered in L.A.Shuvalov's laboratory (Institute of Crystallography), the ionic conductivity of which at certain temperatures sharply increased by several orders of magnitude. In order to understand what was happening in them, they turned to FLNP. Diffraction spectra were obtained in the laboratory, the structure of the crystals was studied, but Nikolay Maximilianovich took on the task of understanding and explaining what was happening there. Already in 1984, he published his prototype in "Letters to JETP". Later, he participated in the discussion of the results obtained in inelastic neutron scattering and became a co-author of several papers.

In the late 1990s, manganites with colossal magnetoresistance were discovered and many theorists and experimenters joined to studying this phenomenon. They also took up this at FLNP together with colleagues from the Kurchatov Institute that discovered the giant isotope effect in manganites. In conclusion, Anatoly Mikhailovich spoke about what he and his colleagues currently work on - alloys with the effect of giant magnetostriction. And he explained that he tried to involve Nikolay Maximilianovich in this phenomenon, but he was very busy with superconductors at that time.

Evgeny Antipov

"His stimulating discussions were important. I remember our discussions with him with pleasure. His main pleasure in life was to talk about physics, to teach the interlocutor something," A.M.Balagurov concluded his report and expressed hope for continued cooperation with theorists.

"Our cooperation with FLNP and theorists began about 30 years ago, communication with Plakida was quite interesting. But today, I want to talk about what we have been doing for the last 15 years and the goal of my speech is to organize more intensive cooperation in a new area," this is how E.V.Antipov (MSU, Skoltech) began his speech. In the report "Metal-ion batteries: problems and prospects" he outlined the state of affairs and prospects for the development of this industry.

V.D.Lakhno (Institute of Mathematical Problems of Biology, Russian Academy of Sciences) spoke about N.M.Plakida and the polaron theory. Since the early 1980s, he collaborated with colleagues at the Laboratory of Theoretical Physics and carried out calculations on the BESM 6 computer at the Leningrad Higher Technical Academy. "Nikolay Maksimilianovich was a super professor, but he did not study the classical polaron that we did. I can say that he was a leader in the investigation of high-temperature superconductors and his book is the best in this field, it is an encyclopedia on the physics of high-temperature superconductors. I approached to him with questions on the theory of strong coupling, we discussed them, I was preparing an answer for him, but he unexpectedly passed away. Polaron is a composite particle, these are fermions and bosons. Unfortunately, we will no longer be able to discuss this with Nikolay Maksimilianovich, but for me he lives in his books."

Viktor Lakhno (on the right)

Olga TARANTINA,
photo by Elena PUZYNINA