Manifestation of exitonic effects in the magneto-oscillations of the intensity of the recombination radiation of 2D electrons

A study is made of the temperature dependence of the magnetooscillations of the recombination radiation of 2D electrons from the photoexcited size-quantization subband in an isolated GaAs/AlGaAs quantum well. It is shown that at high temperatures (T>10 K) the period of the oscillations is determined by the ratio of the intersubband energy splitting and the sum of the electron and hole cyclotron energies. It is found that as the temperature decreases (T<5 K), a new series of oscillations (with the same period but with a larger phase shift), which are associated with the appearance of excitonic states under the Landau levels, appears. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 10, 719–724 (25 November 1996)     

Magnetic moment of a quasi-one-dimensional nanostructure in an inclined magnetic field

Shubnikov-de Haas oscillations in quasi-one-dimensional nanostructures (carbon nanotubes and quantum channels) are investigated. It is shown that two types of aperiodic oscillations arise in such systems: oscillations involving a change in the strength of the magnetic field, and oscillations involving a change in the angle of inclination of the field with respect to the symmetry axis of the system. It is found that the monotonic part of the magnetic moment lies in the plane of size confinement of the system and that the oscillating part has both longitudinal and transverse components. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 7, 549–552 (10 April 1996)     

Spectrum of polariton excitations of a two-dimensional electron plasma in a magnetic field

Polariton excitations associated with magnetoplasma and cyclotron oscillations in a two-dimensional (2D) electron plasma are studied. In contrast to previous works by other authors, it is concluded that there exists a low-frequency nontransmission band in the spectrum of 2D surface magnetoplasma polaritons. Radiative polariton excitations associated with nonuniform cyclotron oscillations of electrons in a 2D system are investigated. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 3, 200–204 (10 August 1998)     

Influence of the beam-forming conditions on the development of space-charge oscillations in a long-pulse relativistic electron beam

The characteristics of the space-charge oscillations of a long-pulse relativistic electron beam in magnetically insulated diodes are determined for different geometries of the electron acceleration section and for explosive-emission cathodes of different materials. The important role of the stream of electrons having high transverse velocities in the evolution of the oscillations is demonstrated, and the laws governing the generation of this stream are determined. Possible mechanisms of the space-charge oscillations are described, taking into account the interaction of the electron stream in the beam halo with the main electron stream, the development of diocotron instability in the stream of electrons emitted by the outer lateral surface of the plasma emitter, and the instability of the space charge of “long-lived” electrons in the beam transport channel. Zh. Tekh. Fiz. 68, 102–106 (April 1998)     

Aharonov-Bohm oscillations in a ring with a quantum well

Aharonov-Bohm oscillations in a ring with a quantum well are investigated in the ballistic regime. It is shown that when trajectories with multiple circuits around the ring are taken into account, the maxima in the conductivity correspond to resonance levels of an isolated ring. The results obtained are in qualitative agreement with the experiment performed by Yakoby, Heiblum, Mahalu, and Shtrikman [Phys. Rev. Lett. 74, 4047 (1995)]: Although the scattering phase of an electron scattered by a quantum well changes by π on passage through each resonance, the Aharonov-Bohm curves for the centers of neighboring resonances are identical. In the simplified interpretation employed by Yakoby et al. the latter result looks like an identical scattering phase in neighboring resonances. Pis’ma Zh. ωksp. Teor. Fiz. 66, No. 9, 605–610 (10 November 1997)     

On the nature of the oscillations of cyclotron absorption in InAs/GaSb quantum wells

The mechanism of oscillations of the half-width and intensity of the cyclotron resonance (CR) line of electrons in a semimetal quantum well based on an InAs/AlSb/GaSb heterostructure is investigated experimentally and theoretically. It is shown that the oscillations of the CR spectrum are due to mixing of states of the spatially separated two-dimensional electrons and holes. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 10, 753–758 (25 November 1998)     

Self-consistent oscillations of the charge in a waveguide

Small oscillations of the charge in a rectangular waveguide are considered. The electromagnetic field generated by these oscillations and its effect on the charge are investigated. It is found that at a certain frequency there is a self-consistent regime of oscillations wherein the charge oscillates under the influence of its self-field in the absence of external forces. The combination of such a charge and the self-consistent alternating field has the property of a quasiparticle, which is named an electromagneton. Zh. Tekh. Fiz. 67, 120–121 (November 1997)     

Magnetic quantum oscillations in the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br

The interlayer magnetoresistance of the organic superconductor κ-(BEDT-TTF)₂Cu[N(CN)₂)Br is measured at ambient pressure and under pressures of up to 12.5 kbar. In addition to the slow Shubnikov-de Haas oscillations with a frequency of ≃150 T observed at P⩾5 kbar, rapid oscillations attributed to the magnetic breakdown orbit enveloping an area equal to 100% of the area of the Brillouin zone are found to emerge above B=20 T. The latter oscillations are observed at ambient pressure as well as under pressures of up to 9 kbar. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 3, 190–194 (10 August 1997) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Energy spectrum of a GaAs (δ-Sn) structure on a vicinal face

The potential profile, electron energy levels, and corresponding wave functions are calculated for a gallium-arsenide structure with a δ-doped tin vicinal face GaAs(0.3°, δ-Sn). Calculated values of the electron densities in the subbands agree well with the quantities obtained from an analysis of the Shubnikov-de Haas oscillations and photoluminescence spectra of the structure. On the basis of the calculated band diagram the lines observed in the photoluminescence spectrum of the GaAs(0.3°, δ-Sn) structure are identified here for the first time as associated with electron transitions on the size-quantization levels in the tin δ-layer. Fiz. Tverd. Tela (St. Petersburg) 39, 1853–1856 (October 1997)     

Spectrum of flexural oscillations of a domain wall with drifting Bloch lines

It is observed that in single-crystalline yttrium iron garnet the amplitude of characteristic flexural oscillations of a 180° domain wall containing Bloch lines increases sharply when drift of the Bloch lines is excited. The resonance frequencies of these oscillations are virtually identical to those of flexural oscillations of a monopolar wall. It is shown experimentally that this phenomenon is most likely caused by a magnetic aftereffect. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 1, 72–75 (10 January 1998)     

Specific features in the magnetoresistance oscillation spectrum from the two-dimensional accumulation layer on (10\overline 1 0) surface

Additional magnetoresistance and Hall effect oscillations have been revealed in the 2D hole system of an accumulation layer on the Te surface. The oscillation frequency was found to be equal to a linear combination of the frequencies of Shubnikov-de Haas 2D-hole conductivity oscillations in the two 2D subbands formed in a near-surface potential. The mechanism responsible for these oscillations is related to the oscillating probability of intersubband scattering in transitions between Landau levels of two size-and magnetic-field-quantized subbands, as they pass near the Fermi level. Fiz. Tverd. Tela (St. Petersburg) 41, 537–539 (March 1999)     

Oscillations of the magnetoresistance in an inclined magnetic field for MIS structures on (100) silicon with a high electron density

At electron densities N _S>6×10⁻² cm⁻²² a second series of oscillations, which are tentatively attributed to population of the second energy subband, is observed in addition to the main series of Shubnikov-de Haas oscillations. A change in phase of the oscillations of the second series is observed at some angle of inclination α_e of the field. The measured value of α_e is used to calculate the ratio of the cyclotron mass to the effective g factor. The maximum possible cyclotron mass is also determined as m _H< 0.32m _e. On this basis it is concluded that the second series of oscillations is due to electrons which have an in-plane effective mass m*≈0.2m _e and which belong to the same valleys of the Fermi surface as in the case of the main oscillations. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 2, 136–140 (25 January 1998)     

Alfvén waves in the electron-nuclear plasma in the peripheral crust of a neutron star as a residual effect of a supernova explosion

The conservation of magnetic flux in the evolution and collapse of massive stars suggests that Alfvén magnetoplasma oscillations can be excited in an isolated neutron star by residual (after the supernova explosion) disturbances of the magnetized electron-nuclear plasma localized in the peripheral crust of the star. The frequencies of the poloidal Alfvén oscillations are calculated in the uniform magnetic field approximation, and it is found that the periods of the oscillations fall into the time interval of the periodicity of radio pulsar radiation. This coincidence of the periods could mean that, at least for some pulsars observed in the radio range, the electromagnetic activity is due to converstion of the energy of magnetoplasma oscillations into electromagnetic radiation. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 9, 593–598 (10 November 1996)     

Magnetic and magnetooptical properties of Au/Cu-wedge/15-Å-NiFe sandwiches

The results of an investigation of the magnetic and magnetooptical properties of Au/Cu-wedge/15-Å-NiFe sandwiches are reported. Oscillations of the equatorial Kerr effect as a function of the copper wedge thickness are observed. The period of these oscillations is found to be of the order of 5–6 Å. The experimentally observed oscillations of the equatorial Kerr effect are attributed to a quantum size effect. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 1, 33–36 (10 January 1998)     

Multiphoton excitation of molecules and the quasienergy spectrum of the anharmonic oscillator

The quasienergy levels of an anharmonic oscillator in a strong external alternating field form two families, transitions between which are forbidden because of the large value of the quasiclassicality parameter of the forced oscillations caused by the external field. This makes it possible to explain the results of a number of experiments on the multiphoton excitation of molecules by infrared radiation. Pis'ma Zh. éksp. Teor. Fiz. 64, No. 1, 13–18 (10 July 1996)     

de Haas-van Alphen oscillations and angular magnetoresistance oscillations in the organic metal κ-(BETS)2GaCl4

Quantum de Haas-van Alphen oscillations and semiclassical angular magnetoresistance oscillations are observed in the quasi-two-dimensional organic metal κ-(BETS)₂GaCl₄. The behavior of these oscillations attests to the existence of two cylindrical Fermi surface sheets with axes perpendicular to the conducting plane. The cross-sectional areas of these cylinders in the conducting plane are equal to about 20 and 100% of the corresponding cross section of the Brillouin zone. It is shown that the many-particle interaction can be suppressed significantly in this compound. Zh. éksp. Teor. Fiz. 115, 205–210 (January 1999)     

Mesoscopic oscillations of the magnetization near Ising impurity centers in strong magnetic fields

The frequency of orientational quantum oscillations of the magnetization near impurity-ion clusters with Ising properties in a saturated magnetic crystal is calculated. It is noted that in compounds of the type Ho_xY_3−x Fe₅O₁₂, where magnetic phase transitions are observed, additional magnetization reversal and magnetic resonance features due to mesoscopic oscillations of the magnetization can be observed at low concentrations x<0.001 and cryogenic temperatures in fields comparable to the intersublattice exchange interaction field. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 6, 445–448 (25 March 1997)     

Stochastic resonance in a nonequilibrium electron-hole plasma

A photogenerated electron-hole plasma, heated in the process of Auger recombination, is studied. It is shown that in the plasma near the threshold for the appearance of uniform relaxational self-excited oscillations, weak noise transforms into a stochastic sequence of large-amplitude spikes. An additional optical periodic signal with amplitude approximately five times smaller than the noise variance, depending on the form of this signal, transforms these stochastic oscillations into low-amplitude quasiharmonic oscillations or into periodic spike self-excited oscillations of enormous amplitude. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 7, 422–427 (10 October 1999)     

Spectrum of flexural oscillations of a 180-degree domain wall in yttrium iron garnet

The long-wave asymptotic behavior of the spectrum of flexural oscillations of a monopolar domain wall in a cubic ferromagnet is found. The experimental results, numerical calculations, and theoretical results obtained for uniaxial ferromagnets are compared. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 10, 797–802 (25 May 1996)