# Laboratory of Theoretical Physics

#### Laboratory Staff

#### Advanced Results

#### Research Techniques

#### Selected Publications

#### Research Focus

*Study of the physical properties of materials with strong quantum fluctuations: high-temperature superconductors, heavy-fermion intermetallic compounds, quantum magnets, materials with colossal magnetoresistance, cobaltites, and quantum dots (led by Valery V. Val’kov).*- Formation of ordered magnetic and superconducting phases and coexistence of superconductivity and antiferromagnetism in strongly correlated systems with heavy fermions, including rare-earth intermetallic compounds.
- Study of the properties of normal, magnetic, and superconducting phases in copper oxides in the framework of the spin polaron concept with regard to the strong non-local relationship between spin degrees of freedom in the localized spin and itinerant fermion subsystems.
- Study of superconductivity in the framework of the Kohn−Luttinger mechanism of new superconducting systems and graphene.
- Quantum transport through magnetic structures at the atomic scale.
- Formation of the superconducting phase with the chiral
*d+id*order parameter and conditions for the occurrence of quantum phase transitions with the variation in the 2D topological index of strongly correlated systems on a triangular lattice. - Spectral and magneto-optical properties of strongly anisotropic quantum magnets.

*Study of propagation of waves in media with regular and random inhomogeneities (led by Val’ter A. Ignatchenko).*- The dynamic susceptibility (Green's function) and the density of states in a sinusoidal superlattice containing simultaneously 2D phase inhomogeneities and 3D amplitude inhomogeneities are investigated. The dynamic susceptibility and density of states of waves in a superlattice at the smooth transition between 3D and 1D inhomogeneities are studied. The spin-wave spectrum in one-dimensional magnon crystals is explored at the periodic modulation of all basic magnetic parameters of a material. Green’s functions of the system of two coupled wave fields of different physical natures in a medium with an arbitrary relation between the mean value and rms fluctuation of the coupling parameter are examined.