Observation of stochastic resonance in a monostable magnetic system

A stochastic resonance on mixed harmonics is observed experimentally in a monostable magnetic system. The curve of the stochastic resonance at higher-order harmonics in systems with a weak nonlinearity is calculated. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 10, 788–792 (25 May 1997)     

Quantum controlled-NOT gate based on a single quantum dot

A realization of a quantum controlled-NOT gate based on a single quantum dot is proposed. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 3, 219–224 (10 August 1996)     

Adiabatic Raman polariton in a Bose condensate

The Raman interaction of optical fields with a Bose condensate is studied in the adiabatic regime. A superposition of operators is found — one annihilating an atom in a metastable state and the other annihilating a photon in resonance with a transition from the ground state to an excited state — which is an adiabatic invariant of the problem (Raman polariton). Possible applications for Bose-condensate diagnostics and development of atomic lasers are proposed. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 7, 473–477 (10 October 1996)     

Sign of the harmonics of the effective interaction in a Fermi gas with repulsion

A general model-independent justification is given for the assertion that a superconducting transition is possible in a Fermi gas with repulsion. It is shown for a wide class of systems that at least one harmonic of the effective interaction is attractive. A relation is found between the harmonics of the effective interaction and the harmonics of the quasiparticle scattering amplitude in the gas approximation. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 640–645 (25 April 1996)     

Modification of porous silicon in ultrahigh vacuum and contribution of graphite nanocrystallites to photoluminescence

A replacement of the adsorbate in porous silicon is carried out in ultra-high vacuum. The photoluminescence line is shifted and quenched as the products of anodization of silicon — silicon hydrides and atomic and molecular hydrogen — undergo thermal decomposition and desorption. Adsorption of molecular chlorine restores the 560 nm photoluminescence band, which we identified as radiation from graphite nanoparticles. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 2, 106–111 (25 January 1996)     

Trapping of Langmuir waves inside an extended inhomogeneity of magnetized plasma

The trapping of Langmuir waves in a cylindrical plasma resonator with a negative density perturbation is observed experimentally. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 4, 280–283 (25 February 1999)     

Spectroscopy of transverse-quantization levels in two-dimensional point contacts in a transverse-focusing geometry

It is shown that the focusing signal in a two-dimensional electron gas contains features corresponding to quantization levels of the transverse motion of an electron in the emitter. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 604–607 (25 April 1996)     

Critical experiments in the search for fermion condensation

The specific features of fermion condensation — a phase transition associated with the rearrangement of the one-particle degrees of freedom in strongly correlated Fermi systems — by which this phenomenon can be detected experimentally are discussed. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 11, 828–833 (10 June 1997)     

On the possibility of a superfluid transition in a Fermi gas of neutral particles at ultralow temperatures

The possibility of triplet Cooper pairing in a Fermi gas of neutral particles in magnetic traps at ultralow temperatures is predicted. Estimates are presented for the superfluid transition temperature. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 4, 273–276 (25 August 1996)     

Chaotic Rabi vacuum oscillations in cavity quantum electrodynamics

It is shown in numerical simulations with two-level atoms moving through a single-mode high-Q cavity that spontaneous emission of a new type — chaotic Rabi vacuum oscillations — arises in the strong atom-field coupling regime. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 11, 801–806 (10 June 1997)     

On a possible mechanism of the formation of large-scale disturbances in Jupiter’s atmosphere as a result of the falling of fragments of Comet Schoemaker-Levy 9

A mechanism explaining the sizes and structure of large-scale disturbances produced in Jupiter’s atmosphere by the impact of the fragments of Comet Shoemaker-Levy is proposed. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 10, 773–777 (25 May 1996)     

Gain coefficient of a high harmonic emitted during the above-threshold ionization of atoms

The problem of the amplification of high harmonics generated during the above-threshold ionization of atoms in a high-power laser wave field is examined for the first time. An estimate of the gain coefficient as a function of the parameters of the atom beam and the pump wave is given. Zh. éksp. Teor. Fiz. 115, 1630–1641 (May 1999)     

Fabry-Perot cavity in the field of a gravitational wave

The structure of the electromagnetic field inside a laser cavity—a gravitational-wave detector—is studied. The properties of the spatial and temporal phases of the standing electromagnetic wave are discussed in detail and the corrections appearing in the electric field of the wave as a result of the action of gravitational radiation on the optical system are determined. Zh. éksp. Teor. Fiz. 113, 398–408 (February 1998)     

Topological structure of the fiber bundle of fermion eigenvectors on a lattice in a magnetic field

It is shown that for an arbitrary lattice Hamiltonian of fermions in a uniform magnetic field the Chern number of the complete fiber bundle of the magnetic Bloch states of this Hamiltonian is equal to zero. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 5, 367–368 (10 March 1996)     

Suppression of nonlocal thermal conductivity in a turbulent plasma

It is shown that anomalous suppression of the electronic thermal conductivity occurs in a weakly collisional plasma as a result of electron scattering not only by charged particles but also by low-frequency turbulent fluctuations. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 579–582 (25 April 1996)     

Scalar propagator in an instanton field in a closed volume

Scalar matter in an instanton field in a closed volume is studied. A compact expression is found for the exact Green’s function of massless scalar particles in the fundamental representation. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 11, 833–836 (10 June 1996)     

Role of stationary photon statistics in a high-Q cavity mode while it is exciting the active laser medium

It has been shown by Yu. M. Golubev, M. I. Kolobov, and I. V. Sokolov, Zh. éksp. Teor. Fiz. 111, 1579 (1997) [JETP 84, 864 (1997)], that when an optical cavity is excited by external radiation from a sub-Poisson laser the cavity mode may be in either a sub-Poisson or a Poisson stationary state. This is not important for a resonant medium which is excited into the upper laser level while interacting with this mode inside the cavity. The degree of regularity of the excitation will be identical to that of the initial light flux incident on the cavity, and this ultimately ensures the same sub-Poisson lasing as for strictly regular pumping of the resonant medium. Zh. éksp. Teor. Fiz. 113, 1223–1234 (April 1998)     

Giant magnetoresistance of vanadium films with a surface magnetic superlattice

Giant (up to 68%) room-temperature magnetoresistance is observed in (110) V films on mica with a periodic system of 5–25 nm wide, thin (⩽10 nm) Co strips, separated by 1–2 nm gaps, grown on the films. The effect is observed only for samples in which the magnetization tilts out of the plane of the film. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 5, 346–349 (10 September 1996)     

Amplification of the generation of the sum-frequency signal in multilayer periodic structures at the edges of the Bragg band gap

A new property of a one-dimensional periodic structure — amplification of the sum-frequency signal arising under the simultaneous action of two laser pulses on this structure with radiation frequencies corresponding to the edges of the fixed Bragg band gap — is experimentally observed and described. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 11, 718–721 (10 December 1999)     

Propagation of zero-exchange spin waves in ferrite films with domain structure

The existence regions and the dispersion relation for zero-exchange spin waves in the presence of symmetric and asymmetric domain structures in yttrium iron garnet films are investigated. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 7, 544–548 (10 April 1996)