The Laboratory of Theoretical Physics (TP) led since 2003 by Doctor of Phys. and Math. Sciences Professor Valery Val’kov, was founded in 1963 and headed by Valter Ignatchenko. That time the main research directions of the Laboratory were connected with experimental works of the Laboratory of Physics of Magnetic Phenomena headed by Leonid Kirensky.

They included the theory of domain structure and magnetization reversal processes, the theory of spin and magnetoelastic waves, the theory of NMR in ferromagnets. The phenomenon of the electronic-nuclear magnetic resonance in ferromagnets was predicted; the new inverse mechanism of the spin echo excitation was theoretically predicted and experimentally realized. Contributions to the theory of dipole systems ordering and to the theory of nonlinear waves and stochasticity origin in dynamic systems were made.

The successful development of this research area had led in 1973 to the separation of the Laboratory of Theory of Nonlinear Processes headed by G.Zaslavsky from the Laboratory of TP. Works on the theory of resonance interaction of laser radiation with a substance were continued later at the Laboratory of Coherent Optics organized in 1975 (A.Popov). The research works on the quantum theory of magnetic ordering in metals and alloys initiated the creation of the Laboratory of Theory of Solid led by E.Kuzmin in 1980.

At present two scientific problems are being solved by the Laboratory researchers. Investigations undertaken in the framework of the first problem (V.Val’kov) are connected with the study of physical properties of materials, in which the significant role is played by strong quantum fluctuations, i.e. high temperature superconductors, intermetallic compounds with heavy fermions, quantum magnets, substances with the colossal magnetoresistance.

Modern methods of theoretical study of strongly correlated systems are being intensively developed and widely used. For the first time, the theory of the superconductive phase of strongly correlated fermions with the account for anomalous components of a strength operator has been developed. Peculiarities of the spectral theorem for spectral intensity of correlation functions in the atomic presentation of strongly correlated systems have been found. The quantum theory of a two-dimensional frustrated antiferromagnet with magnetoelastic coupling has been constructed.

In the framework of the second problem (V.Ignatchenko), waves in media with regular and random inhomogeneities are being studied. The new method of investigation of inhomogeneities effects on the wave spectrum in superlattices has been developed. The wave spectrum of superlattices with an arbitrary thickness of interfaces has been investigated and the possibility of measuring this thickness by spectral methods has been shown. The theory of exchange narrowing of a magnetic resonance line in an inhomogeneous ferromagnet and the theory of coupled magnetoelastic waves in superlattices are being developed.

Among the researchers who worked at the Laboratory there are Doctors of Phys. and Math. Sciences Yu.V. Zakharov, R.G. Khlebopros, G.M. Zaslavsky, V.E. Shapiro, A.K. Popov, V.I. Tsifrinovich, G.P. Berman, I.S. Sandalov, P.I. Belobrov, S.G. Ovchinnikov and Yu.I. Man’kov. Currently they have been working at the Institute of Physics of SB RAS and in various Russian and foreign scientific centers and universities.

The most important scientific results are presented in the following papers:

1. Ovchinnikov S.G., Val’kov V.V. Hubbard Operators in the Theory of Strongly Correlated Electrons- 2004.- Imperial College Press 57 Shelton Street Covent Garden, London WC2H 9HE.- 241 p.
2. Val’kov V.V., Dzebisashvili D.M. Electronic spectrum and temperature of the superconductive transition of strongly correlated fermions with three-center interactions. ZHETF , v. 127, №.3, pp. 686-695 (2005).
3. Gekht R.S., Bondarenko I.N. Quantum spin liquid in the bilayer triangle antiferromagnet. ZHETF, v.128, № 5 (2005).
4. Ignatchenko V. A., V. A. Felk. Exchange narrowing of magnetic resonance linewidths in inhomogeneous ferromagnets. Phys. Rev. B, 71, 094417(2005).
5. Ignatchenko V. A., Tsifrinovich V.I. Nuclear signals in magnetically ordered media. Novosibirsk, Nauka (1993), 150 p.
6. Ignatchenko V.A., Mankov Yu.I. Spectrum of waves in stochastically modulated superlattices. Phys. Rev. B 56, 194 (1997).