Professor Mauro Doria and Director of the Centre Alexey Vagov talked to TASS journalists
Theoretical physicists from Russia and Brazil are working together on a theory that describes novel superconducting materials with potentially high critical temperature. The theory can explain many properties of superconductors with non-trivial topological properties as well as of those with multiple condensates. This was stated to TASS by professor Dr. Mauro Doria (Institute of Physics at the Federal University of Rio-de-Janeiro, Brazil) and professor Dr. Alexei Vagov (Center for Quantum Metamaterials, Moscow Institute for Electronics and Mathematics, HSE University).
TASS, Jun 20th. Russian and Brazilian scientists are to work on theory of novel potentially high-temperature superconducting materials and metamaterials
"Our cooperation with Brazilian colleagues goes back to the start of this century. After these novel superconductors appeared, our mutual interest in cooperation was strengthened as we have a common idea that the existence of these new materials as well as their unique properties can be explained by a new theory that we jointly develop at this moment of time", — said Dr. Vagov.
The scientists hope that the theory they are developing can explain the existence and properties of several types of recently discovered superconductors. These include materials based on compounds of hydrogen and various metals and other elements, as well as the so-called multi-band superconductors with several superconducting condensates.
Another example of these new materials is the so-called topological superconductors, whose near-surface layer has zero resistance. According to Professor Doria, the very fact of the existence of such compounds requires a new theoretical explanation of their superconducting properties, since the classical theory of superconductivity, formulated back in the middle of the last century by John Bardeen, Leon Cooper and John Schrieffer (BCS), does not allow for their existence.
"The main task of my visit to Moscow was to convince my Russian colleagues that the existence and nature of topological insulators and superconductors, one of the most discussed materials in the field of condensed matter physics, can be explained within the framework of a theory that was developed many years ago by Alexei Abrikosov and Evgeny Bogomolny,” said Professor Doria.
According to the Brazilian researcher, the theory developed by Abrikosov in 1957 to describe the magnetic properties of superconducting alloys and the nature of the so-called superconductors of the second type, can explain the existence of new types of superconductors if it is slightly modified. For example, professor Doria proposes to expand the old Soviet theory by exploiting the fact that the particles involved in the flow of current have spin, quantum characteristic that can be roughly depicted as the hypothetical direction in which these particles rotate.
New application for old theories
"The old ideas of Abrikosov, Ginzburg and Landau can be reconfigured in such a way that they explain the nature of topological insulators and superconductors with multiple condensates. This is a completely new direction, which has only just begun to be actively investigated both at the practical and theoretical levels. We hope that we will be able to describe many aspects of these phenomena," Dr. Vagov added.
At the same time, Professor Doria emphasized that he does not exclude the possibility that other theoretical ideas that are now being investigated by the scientific community may be required to explain the nature of all types of superconductors. In his opinion, physicists should conduct both theoretical and practical research in all possible directions, since it is not yet possible to say which theories and which types of superconductors will be the most successful.
"In this case, I like the idea of the Italian economist Vilfredo Pareto, who said that 20% of successful projects can cover losses for 80% of unsuccessful investments. We can say that all the new types of superconductors, including polyhydrides, cuprates, iron and topological superconductors, are the proverbial eggs in the basket. We hope that one of them will hatch and give rise to a superconductor operating at room temperatures and pressures,” the Brazilian physicist explained.
According to Professor Doria, this multi-pronged approach to development of the theory of superconductivity and its practical applications is especially important in the context of the fact that different types of now-researched high-temperature superconductors will have completely different practical applications which are dictated by the peculiar physical properties of each of those materials.
"Superconductors will find the widest application in various sectors of the economy, from lossless electrical grid to high-performance microelectronics. In the first case, we need the ability to transfer large amounts of electricity without loss, and in the second, it is important to be able to control spin and various other properties of charge carriers. To solve the first problem, for example, polyhydride-based superconductors are better suited, and topological superconductors are better suited for microelectronics,” explains the Brazilian researcher.
Union of theory and practice
Solving these problems, according to Doria, will require not only joint theoretical research by Russian and Brazilian physicists, but also practical experiments. They are necessary not only to test theories, but they also provide new "food for thought", including previously unknown phenomena that can hint theorists at how new superconductors work and where they can be applied, even if these experiments themselves do not lead to something useful.
"In 1988, at the March Physics Conference in New York, our colleagues presented what was thought at that time as the first high-temperature ceramic superconductors based on cuprates. After their presentation, all scientists were confident that we would get the first room-temperature superconductors in the coming years, if not months. More than three decades has passed; we still don't have them, yet studies of cuprates have brought us a lot of information about how superconductors work. Many of the words that we now use to depict and explain their properties simply did not exist two or three decades ago, " the Brazilian researcher explained.
In accordance with these principles, as noted by Professor Vagov, Russian scientists and their foreign partners will actively conduct various practical studies of the properties of topological superconductors, as well as other new superconducting materials that can become the basis for new generation electronic devices.
"Researchers are already conducting experiments on the creation and study of such electronics. In fact, our laboratory now combines the forces of specialists from National Nuclear Research University (MEPhI), Higher School of Economics, Moscow Institute of Physics and Technology, and now we want to renew our old ties with Brazilian science, which will lead to the creation of a large international science center where different ideas, theories and experiments will interact and provide new unexpected results," explained Dr. Vagov.