Lev Landau was born in 1908 in Baku. His father was an oil engineer, his mother was a doctor. During his school years, he independently studied differential and integral calculus. At the age of 13, he graduated from school and entered Baku University, and at once to two faculties — physics and mathematics and chemistry. He amazed his colleagues with the ability to instantly perform the most complex mathematical calculations without using either a slide rule, reference books, or tables of logarithms.

Then Landau transferred to the physics department of Leningrad University, from which he graduated in 1927 — nineteen years old. He had a chance to study quantum mechanics "from the heat of the moment", according to the original works of its founders, and he was forever shocked by the beauty of this theory and the power of the human mind expressed in it, the ability of man, according to Landau, to understand and describe what is no longer possible to visualize.

In 1929, Landau was sent abroad by the People's Commissariat of Education and had the opportunity to work for the famous Niels Bohr in Denmark, Ernst Rutherford in England and Wolfgang Pauli in Switzerland for a year and a half. Working with Bohr had a huge impact on Landau — it deepened his understanding of quantum mechanics and to some extent shaped his scientific interests. After the death of Niels Bohr, it was Lev Landau who was called the first theorist in the world.

Nikita Ter-Oganesyan, chief researcher of the Department of Crystallophysics at the Research Institute of Physics of the Southern Federal University, noted that in those years when physicists began to make a bias in specialization, and specialists from different sections often did not understand each other well, Landau had unique knowledge in all sections.

"One of the first widely recognized scientific works of Lev Davidovich Landau is a 1930 work on the diamagnetism of metals, which was written by him as an employee of the Cavendish Laboratory in Cambridge (England) during his scientific trip to universities in Europe. Landau showed that in a magnetic field, the trajectories of free electrons in metals are quantized like the quantization of electron levels in atoms. This leads to the appearance of a small magnetization in metals directed against the direction of the applied external magnetic field. Subsequently, the theory he developed, among other successful applications, allowed to explain the quantum Hall effect discovered in 1980," Nikita Ter—Oganesyan said.

In 1933, to explain the unusual behavior of chromium, iron, cobalt and nickel chlorides in the magnetic field, Landau introduced the concept of antiferromagnetism.

Nikita Ter-Oganesyan, Doctor of Physics and Mathematics at the SFedU, explained that magnets widely used in everyday life are usually ferromagnets, that is, materials in which the magnetic moments of atoms are aligned parallel to each other in the same direction. In antiferromagnets, in the simplest case, the magnetic moments of one half of the atoms are oppositely directed to the magnetic moments of the other half. Antiferromagnets are characterized by a wide variety, are much more common than ferromagnets, and also attract considerable interest from researchers as functional materials.

"However, the greatest influence on the development of many fields, not only physics, but also chemistry and biology, was exerted by two works in 1937, in which Lev Landau formulated general principles for describing phase transitions accompanied by a change in symmetry. A phase in this case is a state of a substance that differs in physical properties from other possible states of the same substance. For example, liquid water, steam and ice are different phases of water, and transitions between them with temperature changes — melting-crystallization and boiling-condensation are phase transitions. In most cases, the different phases differ from each other in their symmetry, and phase transitions are characterized by a violation or restoration of symmetry," Nikita Ter—Oganesyan added.

The scientist explained that in the case of crystals, symmetry is the property of crystals to combine with themselves during rotations, reflections, parallel transfers or a combination of such operations. For example, more than a dozen different crystalline phases of ordinary ice are known, which differ from each other by the mutual arrangement of water molecules in the crystal lattice and, as a consequence, by their symmetry. It was the use of the concept of symmetry that allowed Landau to formulate the foundations of the thermodynamic theory for describing phase transitions, which is now called the Landau theory of phase transitions.

"It will also be useful to note that in the case of the appearance of magnetization in an ordinary magnet, among others, the symmetry with respect to the reversal of time is violated, and the appearance of the Higgs boson in the Standard Model of elementary particles is associated with the violation of much more complex symmetries. In 1950, Vitaly Ginzburg and Lev Landau based on the theory of phase transitions developed by Lev Davidovich created a phenomenological theory of superconductivity. These examples show the breadth of physical phenomena that are described by Landau's theory," Nikita Ter-Oganesyan summed up.

An important development of the Landau theory, which made it possible to expand the understanding of structural and magnetic phase transitions in crystals, was carried out at Rostov State University (now Southern Federal University) by Doctors of Physical and Mathematical Sciences Vladimir Pavlovich Sakhnenko, Yuri Mikhailovich Gufan, Viktor Ivanovich Torgashev, Georgy Mikhailovich Chechin and Vladimir Petrovich Dmitriev.

Currently, the properties of crystals undergoing phase transitions continue to be actively studied at the Southern Federal University both experimentally and using methods developed by Landau and his followers. These are primarily crystals in which ferroelectric, structural and magnetic phase transitions and their combinations occur, as well as alloys and nanostructures, including even virus capsids. The attention of SFedU scientists is also focused on the study of superconductivity, phase transitions in dynamical systems and other studies.

The anniversary of Lev Landau is widely celebrated within the framework of the Decade of Science and Technology, announced by Russian President Vladimir Putin from 2022 to 2031, as the main task of the Decade is to strengthen the role of science and technology and increase people's knowledge about the achievements of domestic science.