SCIENTISTS FROM THE HIGHER SCHOOL OF ECONOMICS AND BRAZIL ARE CREATING A NEW THEORY OF HIGH-TEMPERATURE SUPERCONDUCTIVITY

The Russian and Brazilian scientists have started the joint development of a new theory of high-temperature superconductivity, which will explain the nature of recently discovered superconductors with multiple condensates, as well as the so-called topological superconductors. Mauro Doria, Professor at the Federal University of Rio de Janeiro, and Alexey Vagov, Director of the Center for Quantum Metamaterials at the Higher School of Economics, told HSE Daily about how cooperation will develop.

Russian and Brazilian physicists have begun to jointly develop a new theory of high-temperature superconductivity, which will explain the nature of recently discovered superconductors with multiple condensates, as well as the so-called topological superconductors. Mauro Doria, Professor at the Federal University of Rio de Janeiro, and Alexey Vagov, Director of the Center for Quantum Metamaterials at the Higher School of Economics, told HSE Daily about how cooperation will develop.
"We started cooperation with our Brazilian colleagues back in the early 2000s, and after the appearance of new superconductors, mutual interest in cooperation increased. This is due to the fact that we have a common idea that the existence of all these new materials and their unusual properties, which have recently been discovered by our experimental colleagues, can be explained by one theory, which we are now actively developing," explained Professor Vagov.

Alexey Vagov, photo: Mikhail Dmitriev / Higher School of Economics
Scientists hope that the theory they are developing will help explain the existence and properties of several recently discovered types of superconductors at once. These include materials based on hydrogen compounds and various metals and other elements, as well as so-called multi-zone superconductors, in which there are several superconducting condensates.
Another example of these new materials are the so-called topological superconductors, the surface layer of which 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 in the middle of the last century by John Bardeen, Leon Cooper and John Schrieffer (BCS theory), does not allow their presence.
"My main task is 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 Alexey Abrikosov and Evgeny Bogomolny," said Professor Doria.
According to him, 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 kind is able to explain the existence of many new types of superconductors with a slight expansion, including the addition of the concept of spin in particles involved in the movement of current.
A new application for old theories
"The old ideas of Abrikosov, Ginzburg and Landau can be turned 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 now begun to be actively explored both on a practical and theoretical level. We hope that we will be able to explain many of these phenomena," Professor Vagov added.
At the same time, Professor Doria stressed that he does not exclude the possibility that other theoretical ideas may be needed to explain the nature of all types of superconductors, which are currently being developed by the scientific community. In his opinion, physicists should conduct both theoretical and practical research in all possible directions, since it is currently impossible to say which theories and which types of superconductors will be the most successful.

Mauro Doria, photo: Mikhail Dmitriev / Higher School of Economics
"In this case, I like the idea of the Italian economist Wilfredo Pareto the most, who said that 20% of successful projects discourage 80% of unsuccessful investments. It can be said that all new types of superconductors, including polyhydrides, cuprates, iron and topological superconductors, are kind of eggs in one basket. We hope that one of them will hatch and give rise to a superconductor operating at room temperatures and pressures," explained the Brazilian physicist.
According to Professor Doria, the multi-vector development of the theory of superconductivity and its practical applications is especially important in the context of the fact that different types of high-temperature superconductors currently being developed will have completely different practical applications related to the peculiarities of the physical properties of such materials.
"Superconductors will find the widest application in various sectors of the economy, starting with the delivery of electricity to cities and ending with 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 have the ability to control the spin of charge carriers. For example, polyhydride—based superconductors are better suited to solve the first problem, and topological superconductors are better suited for microelectronics," explains the Brazilian researcher.
Union of Theory and Practice
According to Doria, solving these problems will require both joint theoretical research by Russian and Brazilian physicists and practical experiments. They are necessary not only to test theories, but also to find new food for the mind, including previously unknown phenomena that can tell theorists how new superconductors work and where they can be used, even if these experiments themselves do not lead to concrete results.
"In 1988, at the March physics conference in New York, the first high-temperature ceramic superconductors based on cuprates were presented, as it seemed to everyone at the time. After their discovery, everyone was confident that we would get the first “indoor” superconductors in the coming years. More than three decades have passed, this has not happened yet, but cuprate research has brought us a lot of information about how superconductors are arranged. Many of the terms that we now use to explain their properties simply did not exist two or three decades ago," explained the Brazilian researcher.
In accordance with these principles, as Professor Vagov noted, 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 unites the forces of specialists from the National Research Institute of MEPhI, HSE, MIPT, and we want to renew old ties with Brazil, which will lead to the creation of a large scientific center where different ideas will unite and interact," explained Professor Vagov.
According to him, young Brazilian specialists will come to Russia to work within the framework of the HSE MIEM Center for Quantum Metamaterials. These researchers will work together with their Russian colleagues to create a new theory of superconductivity and its practical applications in the development of microelectronics.
As Professor Vagov noted, these theoretical studies and practical experiments will be aimed primarily at studying the properties of new superconducting materials, including those in which there are several condensates and which at the same time have a non-trivial topology. Scientists hope to present the first results of these theoretical and practical works to the public in the near future.
Date of publication: 01/25/2024
By Alexander Telishev, especially for HSE Daily