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The ballistic method for obtaining a dense radiating plasma and the possibilities of using this method to pump solid-state lasers are investigated. The plasma was obtained experimentally by heating the working gas in a ballistic plasmatron. A vortex chamber is proposed for transferring energy into the plasmatron - laser system., Comment: 4 pages, 3 figures, pdf file

We calculate the current density in a semiconductor superlattice with parabolic miniband under crossed non-quantizing electric and magnetic fields. The Corbino disk geometry is considered. The current-voltage curve contains oscillations with period proportional to the magnetic field. The possibility is shown of the negative absolute conductivity. The Ampere-Gauss characteristics also contain overshoots under high enough electric fields. In all cases, the peaks smear with temperature rising., Comment: 5 pages, 2 figure, in Russian

We calculate the current density in a semiconductor superlattice with parabolic miniband under crossed non-quantizing electric and magnetic fields. The Corbino disk geometry is considered. The current-voltage curve contains oscillations with period proportional to the magnetic field. The possibility is shown of the negative absolute conductivity. The Ampere-Gauss characteristics also contain overshoots under high enough electric fields. In all cases, the peaks smear with temperature rising., Comment: 8 pages, 4 figures

Mirror matter is considered as a candidate for dark matter. In connection with this an experimental search for neutron - mirror neutron (nn') transitions has been carried out using storage of ultracold neutrons in a trap with different magnetic fields. As a result, a new limit for the neutron - mirror neutron oscillation time has been obtained, tau_osc >= 448 s (90% C.L.), assuming that there is no mirror magnetic field larger than 100 nT. Besides a first attempt to obtain some restriction for mirror magnetic field has been done., Comment: 11 pages, more detailed analysis of data

The idea of a hidden sector of mirror partners of elementary particles has attracted considerable interest as a possible candidate for dark matter. Recently it was pointed out by Berezhiani and Bento that the present experimental data cannot exclude the possibility of a rapid oscillation of the neutron n to a mirror neutron n' with oscillation time much smaller than the neutron lifetime. A dedicated search for vacuum transitions n->n' has to be performed at weak magnetic field, where both states are degenerate. We report the result of our experiment, which compares rates of ultracold neutrons after storage at a weak magnetic field well below 20 nT and at a magnetic field strong enough to suppress the seeked transitions. We obtain a new limit for the oscillation time of n-n' transitions, tau_osc (90% C.L.) > 414 s. The corresponding limit for the mixing energy of the normal and mirror neutron states is delta_m (90% C.L.) < 1.5x10-18 eV., Comment: 16 pages, 8 figures, 2 tables

The static and high-frequency differential conductivity of a one-dimensional superlattice with parabolic miniband, in which the dispersion law is assumed to be parabolic up to the Brillouin zone edge, are investigated theoretically. Unlike the earlier published works, devoted to this problem, the novel formula for the static current density contains temperature dependence, which leads to the current maximum shift to the low field side with increasing temperature. The high-frequency differential conductivity response properties including the temperature dependence is examined and opportunities of creating a terahertz oscillator on Bloch electron oscillations in such superlattices are discussed. Analysis shows that superlattices with parabolic miniband dispersion law may be used for generation and amplification of terahertz fields only at very low temperatures., Comment: 10 pages, 5 figures

Distribution function and current density in a one-dimensional superlattice with parabolic miniband are calculated. The current dependence on the temperature coincides with experimental data. Generalization is carried out to quasi-two-dimensional superlattice with paraboloidal miniband. For a sample opened in Y direction with dc current in X direction, a novel nonequilibrium phase transition is found, namely, appearing a spontaneous transverse electric field under temperature rising., Comment: 9 pages, 6 figures

Results are presented of studying the stochastic resonance (SR) in conductors with bcc lattice and narrow conduction band. In such materials, SR has a feature, namely, the weak-signal gain as a function of the additive and non-correlated noise level can have two maxima, i.e., double SR takes place., Comment: 2 pages, 2 figures

The response is studied of a narrow-band conductor with bcc lattice to a low-frequency signal under presence of a high-frequency signal. In a high enough dc electric field Ex, the conduction electrons form a bistable system, which results in spontaneous appearance of a transverse electric field Ey. Ac field along y axis leads to amplification of the low-frequency signal with non-monotonous dependence of the gain on the high-frequency field amplitude, so that vibrational resonance takes place. Besides, high-frequency field induced nonequilibrium phase transition is found., Comment: 5 pages, 5 figures

In present work, we investigate the second harmonic generation in a superlattice under presence of the carrier density gradient. We show that the second harmonic intensity can be comparable with that of the current fundamental harmonic in that case., Comment: 10 pages, 3 figures

Dynamics is studied of an electron in a quasi-one-dimensional ballistic ring under circularly polarized electromagnetic field propagating along the normal to the ring plane. The average emission intensity from the ring is calculated. The value and direction of the electron average angular velocity in the ring depend on the incident wave parameters. It is found that the ring average dipole moment can remain constant under certain conditions. Possibility is shown of higher harmonics enhancement in the ring radiation spectrum., Comment: 8 pages, 6 figures

We study electron dynamics in a quasi-one-dimensional ballistic ring driven by two crossed high-frequency electric fields parallel to the ring plane. The averaged dipole moment and emission intensity are calculated. The emission polarization coincides with the direction of one of the fields. A possibility is shown of the polarization switching to perpendicular direction under changes in the field amplitudes and frequencies., Comment: 7 pages, 2 figures

A fluctuation theory is presented for the nonequilibrium second order phase transition in a quasi-two-dimensional electron gas. A transverse (with respect to the current through the sample) spontaneous electric field as an order parameter and a driving longitudinal field as a control parameter are used. In addition to the earlier results, the intrawell dynamics is taken into account. Non-monotonous behavior of the periodic signal gain as a function of the noise power (stochastic resonance) is predicted., Comment: 9 pages, 2 figures

A ballistic ring in presence of collinear dc and high-frequency electric fields is considered. A possibility is demonstrated of the system switching between two states by changing the strength of dc and/or high-frequency field. It leads to hysteretic behavior of the ring dc dipole moment as a function of the dc electric field., Comment: 3 pages, 1 figure