Magnon instability in the free-carrier absorption in magnetic semiconductors under a strong d.c. magnetic field

The magnon damping in an electron-magnon system in the presence of a laser beam and a d.c. magnetic field is discussed. It is shown that near the laser-cyclotron resonance, and for the laser beam propagating perpendicularly to the magnetic field the magnon population in a relatively narrow range of k may grow with time.     

Magnetothermal effect in semiconductors in strong magnetic fields

We have derived an expression for the adiabatic differential temperature change $\text{(}\text{?T}\text{?H}\text{)}{}_{\mathrm{s}}$ of a semiconductor in the extreme quantum region. The transition to non-degeneracy is characterised by a sharp negative dip in $\text{(}\text{?T}\text{?H}\text{)}{}_{\mathrm{s}}$, which may be greatly modified by the Zeeman splitting. A numerical calculation of $\text{(}\text{?T}\text{?H}\text{)}{}_{\mathrm{s}}$ has been made for GaAs with electron concentrations of 1.2 × 10¹⁶ and 3.8 × 10¹⁶ cm^?3 at temperatures of 2,1 and 0.5 K.     

Magnon instability by a radiation field in magnetic semiconductors and strong d.c. magnetic fields

The magnon damping in an electron-magnon system in the presence of a laser beam and a d.c. magnetic field is discussed. It is shown that near the laser-cyclotron resonance, and for the laser beam propagating perpendicularly to the magnetic field the magnon population in a relatively narrow range of k may grow with time.     

Electron and phonon temperature fields in bounded semiconductors in a magnetic field

The electron and phonon temperature distributions in a semiconductor sample with finite dimensions, placed in a thermostat with an arbitrary, fixed temperature profile, were studied. Heat transfer between the thermostat and the electrons and phonons through the wall is assumed to be arbitrary, while the magnetic field is assumed to be weak.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 73–78, August, 1987.     

A new type of phonon instability in semiconductors exposed to a strong electric field

The damping of a phonon γ_q is calculated for the case when the electron acceleration influenced by a strong electric field for the time of the electron-phonon interaction is essential.     

Amplification of optical phonons by a radiation field in semiconductors under strong magnetic fields

The effect of a strong magnetic field on the optical phonon damping in an electron-phonon system is discussed. It is found that as the laser frequency approaches the electron cyclotron frequency the optical phonon population may become unstable.     

Interband absorption and luminescence in small quantum dots under strong magnetic fields

Interband absorption and luminescence of quasi-two-dimensional, circularly symmetric, N_e-electron quantum dots are studied at high magnetic fields, 8B60 T, and low temperatures, T2 K. In the N_e=0 and 1 dots, the initial and final states of such processes are fixed, and thus the dependence on B of peak intensities is monotonic. For larger systems, ground state rearrangements with varying magnetic field lead to substantial modifications of the absorption and luminescence spectra. Collective effects are seen in the N_e=2 and 3 dots at “filling fractions” and .     

On the resonance two phonon absorption in zero-gap semiconductors

The resonance two phonon process is used to explain innormal value and temperature dependence of oscillator strength of additional phonon mode observed in zero-gap semiconductors.     

Anomalous behavior of the low-temperature nernst-ettingshausen coefficient of semiconductors in strong magnetic fields

We show that the transition to nondegeneracy induced in a semiconductor at very low temperatures by a sufficiently strong magnetic field should give rise to an anomalous behavior of the Nernst-Ettingshausen coefficient.     

Free carrier absorption in quantizing magnetic fields: Nonpolar optical phonon scattering

A quantum theory of free carrier absorption in nondegenerate semiconductors and in strong magnetic fields which was previously developed to treat the case when acoustic phonon scattering dominates the free carrier absorption process [1] is extended to treat the case when nonpolar optical scattering is important. When the electromagnetic radiation field is polarized parallel to the direction of the applied magnetic field, results are obtained which are similar to those when acoustic phonon scattering is dominant. The free carrier absorption is an oscillatory function of the magnetic field which on the average increases in magnitude with the magnetic field. However, more structure in the free carrier absorption occurs when nonpolar optical phonon scattering dominates. This is due to the fact that there are two periods in the oscillatory magnetic field dependence associated with the emission or the absorption of optical phonons during the intraband transitions. When the cyclotron frequency exceeds the sum of the photon and optical phonon frequencies, i.e. ω_c > θ + ω_o, the free carrier absorption is predicted to increase linearly with magnetic field when ?ω_c? k_BT. The magnetic field dependence of the free carrier absorption can be explained in terms of phonon-assisted transitions between the various Landau levels in a band involving the emission and absorption of optical phonons.     

Spin wave amplification by a radiation field in free-carrier magnetic semiconductors

The rate of change in the magnon population due to scattering by free carriers in the presence of a laser field is calculated. It is found that spin waves propagating parallel to the direction of propagation of the radiation field may be amplified over a relatively narrow band of q values.     

Plasmon-assisted sound amplification in semi-conductors under strong magnetic fields

We derive an expression for the contribution from plasma effects to the sound amplification in piezo-electric semiconductors subjected to a strong d.c. magnetic field applied parallel to the drift field. It is shown that this contribution largely differs from that in the absence of a magnetic field both in the strength of the effect and in angular distribution of the emitted phonons.     

Microwave absorption in the Kondo lattice of CeB6 in strong magnetic fields

The characteristic features of microwave (30–120 GHz) magnetoabsorption in the magnetic Kondo lattice of CeB₆ at liquid-helium temperatures in strong magnetic fields are investigated. It is discovered that the absorption structure is the result of the superposition of the ESR of the cerium 4 f electrons, which has a pronounced doublet structure, and features whose position does not depend on the radiation frequency and which are associated with transitions in the magnetic phase diagram of CeB₆. The character of the absorption in the vicinity of the ESR can be linked to the splitting of the ² F _5/2 state in the crystal field; here the g factor is substantially renormalized from g=2.06±0.03 to g=1.83±0.03 as the temperature decreases from 4.2 K to 1.8 K, respectively. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 6, 431–435 (25 March 1996)     

Effect of nonpolar optical phonon scattering on free-carrier absorption in heavily doped n-type germanium

The effect of nonpolar optical phonon scattering on the free-carrier absorption in n-type semiconductors such as germanium has been investigated quantum mechanically in quantizing magnetic fields. It is assumed that the energy band of electrons in semiconductors is nonparabolic and the dominant scattering mechanism for electrons in solids is that of nonpolar optical phonon scattering. When the radiation field is polarized parallel to the magnetic field, the absorption coefficient will be of complex value due to the interaction of the radiation field and the optical phonon field with electrons in semiconductors. Results show that real and imaginary parts of the absorption coefficient oscillate quite considerably with the magnetic field in the high fields for the heavily doped n-type Ge. Both real and imaginary parts of the absorption coefficient appear as positive and negative values when changing the magnetic field. In low magnetic fields, the imaginary part of the absorption coefficient disappears. However, if the density of electrons increases, the imaginary part of the absorption coefficient will increase with the magnetic field in low fields. Moreover, it is also shown that the amplitudes of oscillations for the real and imaginary parts of the absorption coefficient do not vary in a regular trend with the density of electrons.     

Deuteron under strong magnetic fields: Skyrme model study

We explore the deuteron under strong magnetic fields in Skyrme models. The effects of the derivative dependent sextic term in the Skyrme Lagrangian are investigated, and the rational map approximation is used to describe the deuteron. The influences of strong magnetic fields on the electric charge distribution and mass of the deuteron are discussed.     

Quantum transport in an anisotropic two-dimensional system under strong magnetic fields

Characteristics of the conductivity tensor are obtained in an anisotropic two-dimensional system where the Fermi surface is given by elliptic form. The anisotropy of the transverse conductivity _xx and _yy depends strongly on the range of scattering potentials: It becomes maximum in case of short-ranged scatterers, and decreases with the increase of the range. The conductivity becomes isotropic in the limit of slowly-varying scatterers if the scattering potential is isotropic. The Hall conductivity is, on the other hand, not affected by the anisotropy strongly.     

Grantmakher-Kaner effect in strong magnetic fields

Gantmakher-Kaner (GK) effect in a compensated metal is studied theoretically. The dependence of the amplitude of GK oscillations from the polarization of exciting radio-frequency field is found. Effect results from the excitation of doppleron in the plate. In polarization, in which the doppleron exists, the part of skin-layer field energy, contained in harmonics with the length close to cyclotron displacement of resonant carriers, is carried into the slab by doppleron. This results in decreasing of GK oscillations in this polarization in comparison with an opposite one.