From complex quantum effects to the manipulation of nanostructures, the physics of the 21st century is advancing in Russia.

Many refer to the 20th century as the century of physics. This era witnessed fundamental discoveries in the realm of the micro-world, enabling the harnessing of nuclear energy, the creation of microelectronics, and the development of unique radiation sources such as lasers and X-ray machines. Due to the close connection between these discoveries and the interests of the military industry, nuclear physics, plasma physics, and laser physics experienced a significant boom in the mid-20th century. The Soviet Union was no exception, emerging as one of the global leaders in these fields. Following the collapse of the USSR, Soviet physicists found permanent or temporary positions in scientific centers abroad due to their high level of expertise. Many maintained previous connections, which helped preserve the global level of research in certain institutes and universities in Russia.

With the improvement of funding for science in the 2000s and 2010s, these centers became growth points, allowing scientists who remained in Russia or decided to return to gather strong teams. The physics of the 21st century has opened new horizons for research, primarily related to ultra-precise control of micro-objects and their states, including nanostructuring, quantum informatics, and the generation of ultra-short pulses. These areas are actively developing in modern Russia alongside more traditional fields.

Delving into the atomic nucleus in search of new particles and undiscovered laws

One of the main directions in modern physics is the study of matter at the level of its most fundamental components — subatomic particles. From school, we know that all bodies consist of atoms, atoms of electrons and nuclei, and nuclei of protons and neutrons. However, in the 20th century, physicists discovered that this world is much richer and more interesting. It turned out that protons and neutrons are made up of even smaller particles — quarks, which can combine to form other particles such as pions, mesons, kaons, etc. Additionally, there are particles of an entirely different type: nearly undetectable neutrinos generated in nuclear reactions, and antiparticles that are identical to our ordinary particles but carry an opposite charge. For instance, while the electron is negatively charged, its antiparticle, known as a positron, is positively charged. Later, particles that resemble our familiar ones but are heavier were also discovered: for example, the electron has heavier counterparts known as muons and tau leptons.

All these discoveries were linked to the invention and development of accelerators — devices designed to accelerate particles to high and ultra-high energies. The accelerated particles are then collided with one another, resulting in new particles being born in the initiated nuclear reactions. The higher the energy of the accelerated particles, the more new particles can be produced during the collision. Consequently, scientists built accelerators of ever-increasing sizes. The largest accelerator currently is the Large Hadron Collider, constructed in Switzerland by the European Organization for Nuclear Research (CERN). The size of this accelerator is so immense that no single country could afford its construction, which is why most developed countries, including Russia, played a significant role in its development and the creation of particle detectors for it.

One of the most significant Russian achievements in the field of subatomic physics in recent years, and perhaps even decades, has been the discovery of new chemical elements at the Joint Institute for Nuclear Research (JINR) in Dubna. In the 1950s, Georgy Nikolayevich Flyorov organized the Laboratory of Nuclear Reactions (LNR), which was later headed by Yuri Tsolakovich Oganessian after his departure in the late 1980s. For decades, the LNR has remained a world leader in the synthesis of nuclei with record-high proton numbers, or chemical elements with the largest atomic numbers. By 1952, elements with atomic numbers up to 100 had been synthesized. Now there are 118, with the majority obtained through the efforts of LNR staff. In recognition of their contributions, the 105th element was named dubnium, the 114th — flerovium, the 115th — moscovium, and the most recently synthesized 118th element in 2010 was named oganesson. This is only the second instance in history where an element was named after a living person.

Currently, the LNR is working on creating a factory for superheavy elements — it is not enough to just create new elements; their properties also need to be studied, which requires reliable methods for obtaining them in sufficient quantities. In 2022, scientists set a record by synthesizing over 238 atoms of superheavy elements. They even began researching the chemical properties of the 112th and 114th elements.

However, JINR is renowned not only for the LNR and the synthesis of superheavy elements. For over 30 years, the Nuclotron heavy ion accelerator has been operational here. Heavy ions contain many protons and neutrons, and therefore quarks, which they consist of. Colliding such nuclei allows for the study of not the birth of new particles, but the properties of nuclear matter. Currently, a new, even more powerful accelerator — NICA — is being built based on this facility, which is one of six mega-science projects supported by the government of the Russian Federation. NICA, which is expected to begin operations in the near future, will be a unique installation on a global scale, where nuclear matter and its transformations in a highly compressed state will be studied, a state that occurs in nature only in exotic cosmic objects such as neutron stars or the cores of supernovae.

In addition to NICA, several other accelerators are part of the mega-science projects. One of them, the Super Charm-Tau factory, is planned to be built in Novosibirsk by the Institute of Nuclear Physics of the Siberian Branch of the Russian Academy of Sciences (INP SB RAS). This will be an accelerator for electrons and positrons, the collisions of which are intended to be studied here. The main goal of the project is to produce and study tau leptons, very heavy "brothers" of electrons that were discovered back in 1975 but have been virtually unexplored until now.

Currently, several smaller electron-positron accelerators are operating at INP SB RAS, where unexpected results are sometimes obtained during experiments. For example, observations of the transformation of colliding electrons and positrons into other nuclear particles — pions — have shown that the probability of such a transformation is higher than measured by other groups. The reason for this remains to be understood. It is possible that some yet unknown particles are to blame.

A separate important type of accelerator for applications is the electron synchrotrons — sources of bright X-ray radiation, which can be used to study the atomic structure of materials, biological molecules, and active substances of drugs. Russia lacks synchrotron sources of modern standards. The largest currently operational one, the Kurchatov Synchrotron Radiation Source (KISI) in Moscow, was designed back in the late 1980s. Therefore, one of the mega-science projects is the new synchrotron source SKIF (Siberian Circular Photon Source), which is under construction in Koltsovo near Novosibirsk. Like KISI, this project is primarily developed and implemented through the efforts of INP SB RAS, the leading Russian center in the field of electron accelerators.

Another major project where specialists from INP SB RAS play a leading role is the Compton gamma-ray source with record brightness, planned for construction at the National Center for Physics and Mathematics (NCFM) near Sarov. Its opening will allow the study of the interaction of light particles — photons — with atomic nuclei.

In Gatchina, at the Petersburg Institute of Nuclear Physics (PINP), which is part of the Kurchatov Institute, another mega-science project called PIK is expected to be launched soon. It represents a research nuclear reactor designed to generate neutron fluxes. Like X-ray radiation, neutron radiation can be used to study substances and molecules. Its unique ability lies in the fact that neutrons allow for the identification of which specific atoms are present in a substance. Moreover, they have different penetrating and absorbing capabilities, and therefore neutrons and X-rays can complement each other in research.

Beyond fundamental physics and materials science, accelerators are also used in medicine. For instance, accelerated protons can be employed to remove cancer tumors. A method known as proton beam therapy operates similarly to X-ray therapy. However, unlike X-rays, protons can penetrate deep into a substance and deliver a dose of radiation precisely at that depth. This means they can be used even when there is no direct access to the tumor. In Russia, centers conducting such operations have been established in Gatchina based on PINP, in Troitsk based on the Institute for Nuclear Research of the Russian Academy of Sciences (INR RAS), and in Protvino based on the branch of the P.N. Lebedev Physical Institute of the Russian Academy of Sciences (FIAN).

Another unusual application of nuclear technologies is muonography. Muons — particles similar to electrons but heavier — arrive in large numbers from space and can pass through large objects, slightly deviating from a straight trajectory if there are cavities inside. They allow, for example, the detection of magma reservoirs within volcanoes, which is crucial for predicting eruptions. In recent years, muonography has also been applied to study cultural heritage objects. For example, muons helped discover an