Zheleznogorsk, Russia
Zheleznogorsk, Russia

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Kolovsky A.R.,RAS Kirensky Institute of Physics
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2017

We theoretically analyze the ground state of weakly interacting bosons in the flux ladder - the system that has been recently realized by means of ultracold atoms in the specially designed optical lattice [M. Atala, M. Aidelsburger, M. Lohse, J. T. Barreiro, B. Paredes, and I. Bloch, Nat. Phys. 10, 588 (2014)1745-247310.1038/nphys2998]. It is argued that, for the system parameters corresponding to two degenerate minima in the Bloch dispersion relation, the ground state is a fragmented condensate. We study the Bogoliubov depletion of this condensate and discuss the role of boundary conditions. © 2017 American Physical Society.

Bulgakov E.N.,RAS Kirensky Institute of Physics | Sadreev A.F.,RAS Kirensky Institute of Physics
Optics Letters | Year: 2014

A design of all-optical diode in L-shaped photonic crystal waveguide is proposed that uses the multistability of single nonlinear Kerr microcavity with two dipole modes. Asymmetry of the waveguide is achieved through different couplings of the dipole modes with the left and right legs of the waveguide. Using coupled mode theory we demonstrate an extremely high transmission contrast. The direction of optical diode transmission can be controlled by power or frequency of injected light. The theory agrees with the numerical solution of the Maxwell equations. © 2014 Optical Society of America.

Kolovsky A.R.,RAS Kirensky Institute of Physics
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

We discuss a method for creating bright matter solitons by loading a Bose-Einstein condensate of atoms in a driven tilted optical lattice. It is shown that one can realize the self-focusing regime for the wave-packet dynamics by properly adjusting the phase of the driving field with respect to the phase of Bloch oscillations. If atom-atom interactions are larger than some critical value gmin, this self-focusing regime is followed by the formation of bright solitons. Increasing the interactions above another critical value gmax makes this process unstable. Instead of soliton formation one now meets the phenomenon of incoherent self-trapping. In this regime a fraction of atoms is trapped in incoherent localized wave packets, while the remaining atoms spread ballistically. © 2010 The American Physical Society.

Martynov S.N.,RAS Kirensky Institute of Physics
JETP Letters | Year: 2012

A new incommensurate magnetic structure with a locally triangular orientation of spins has been proposed for a two-subsystem magnet with frustrated intersystem exchange and competition between exchanges in one of the subsystems. When the temperature is lowered, this structure appears from the antiferromagnetic state after a first-order phase transition. It transfers to the Yafet-Kittel triangular structure when the threshold conditions for the exchange interactions are fulfilled. An increase in the length of the frustrated exchange bonds leads to the appearance of an incommensurate phase with the local antiferromagnetic orientation of the sublattices in each subsystem between the commensurate antiferromagnetic and Yafet-Kittel phases. © 2012 Pleiades Publishing, Ltd.

Ovchinnikov S.G.,RAS Kirensky Institute of Physics
JETP Letters | Year: 2011

The pressure-temperature phase diagram of magnesiowüstite has been constructed using the many-electron LDA+GTB approach. The phase diagram includes a quantum critical point at P c = 55 GPa and has a symmetrical distribution of high-spin and low-spin states. The existence of a metallic state in a narrow temperature range above the critical point is predicted. © 2011 Pleiades Publishing, Ltd.

Quantum dynamics of a charged particle in a two-dimensional (2D) lattice subject to magnetic and electric fields is a rather complicated interplay between cyclotron oscillations (the case of vanishing electric field) and Bloch oscillations (zero magnetic field), details of which has not yet been completely understood. In the present work we suggest to study this problem by using cold atoms in optical lattices. We introduce a one-dimensional (1D) model which can be easily realized in laboratory experiments with quasi-1D optical lattices and show that this model captures many features of the cyclotron-Bloch dynamics of the quantum particle in 2D square lattices. © 2012 Higher Education Press and Springer-Verlag Berlin Heidelberg.

Ovchinnikov S.G.,RAS Kirensky Institute of Physics
Journal of Experimental and Theoretical Physics | Year: 2013

Possible variants of the Mott-Hubbard phase transitions at high pressure in systems with spin crossovers are considered. Owing to the universal character of the dependence of the effective Hubbard parameter U eff(d n ) on the average number of d electrons, which is determined by the presence of spin crossovers, cascades of insulator-metal-insulator phase transitions in systems with d 3, d 6, and d 8 configurations become possible. Moreover, the systems with d 6 configuration can exhibit transitions from a metal in the absence of external pressure to an insulator at high pressure. © 2013 Pleiades Publishing, Ltd.

Volkov N.V.,RAS Kirensky Institute of Physics
Physics-Uspekhi | Year: 2012

A topical and highly promising aspect of the field of spintronics is the physics involved in the flow of a spin-polarized current through magnetic tunnel structures. This review focuses on manganite-based structures, which are appealing for their high Curie temperature, highly spin-polarized conduction elec- trons, high chemical stability, and well-developed fabrication technology. Particular emphasis is placed on some novel ap- proaches to studying the tunnel structures, including the use of planar geometry and the application of combined external factors (microwave and optical radiation) to investigate spin- polarized transport. © 2012 Uspekhi Fizicheskikh Nauk, Russian Academy of Sciences.

Kolovsky A.R.,RAS Kirensky Institute of Physics
EPL | Year: 2011

This paper proposes a simple setup for introducing an artificial magnetic field for neutral atoms in 2D optical lattices. This setup is based on the phenomenon of photon-assisted tunneling and involves a low-frequency periodic driving of the optical lattice. This low-frequency driving does not affect the electronic structure of the atom and can be easily realized by the same means which are employed to create the lattice. We also address the problem of detecting this effective magnetic field. In particular, we study the center-of-mass wave packet dynamics, which is shown to exhibit certain features of cyclotron dynamics of a classical charged particle. Copyright © EPLA, 2011.

Parshin A.M.,RAS Kirensky Institute of Physics
International journal of molecular sciences | Year: 2013

Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface.

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