Conductivity of a semiconductor superlattice in a transverse magnetic field

The conductivity of a semiconductor superlattice in a magnetic field perpendicular to the superlattice axis is calculated. The dependence of the conductivity on the magnetic field strength is studied. It is found that there is a magnetic-field range where the resistivity is proportional to the magnetic field strength.     

Attenuation of electromagnetic waves in a semiconductor superlattice in a magnetic field

Magnetoplasma waves and inhomogeneous (complex) waves in an infinite semiconductor superlattice in a magnetic field are studied, and dispersion curves are obtained. It is shown analytically and numerically that, in periodic structures, among inhomogeneous waves, there are many complex waves for which the imaginary part of the wave vector is greater than the real part. The effect of dissipation in a medium on the dispersion curves of magnetoplasma waves is examined. The dependence of the minimum phase velocity on the collision frequency and the magnetic field strength is studied.     

Nonlinear second harmonic generation by light wave-plasma interaction in oscillating magnetic field

The nonlinear generation of second harmonic electromagnetic waves in a thin inhomogeneous (dense and rarefied) plasma layer (of lengthd) by obliquely and normally incident light waves is analyzed. We consider the effect of an external time-dependent magnetic field on the generation and amplification of waves. Two cases are considered, when the magnetic field oscillates at a frequency (i) equal to and (ii) double that of the incident wave. For normal incidence, waves are not radiated in case (i), while in case (ii) the second harmonics are radiated equally from the plasma boundaries atx=0 andx=d. For a rarefied plasma, the second harmonics are radiated with equal amplitudes in both cases.     

太赫兹场和倾斜磁场对超晶格电子动力学特性调控规律研究

微带超晶格在磁场和太赫兹场调控下表现出丰富而复杂的动力学行为, 研究微带电子在外场作用下的输运性质对于太赫兹器件设计与研制具有重要意义. 本文采用准经典的运动方程描述了超晶格微带电子在沿超晶格生长方向(z方向)的THz场和相对于z轴倾斜的磁场共同作用下的非线性动力学特性. 研究表明, 在太赫兹场和倾斜磁场共同作用下, 超晶格微带电子随时间的演化表现出周期和混沌等新奇的运动状态. 采用庞加莱分支图详细研究了微带电子在磁场和太赫兹场调控下的运动规律, 给出了电子运行于周期和混沌运动状态的参数区间. 在电场和磁场作用下, 微带电子将产生布洛赫振荡和回旋振荡, 形成复杂的协同耦合振荡. 太赫兹场与这些协同振荡模式之间的相互作用是导致电子表现出周期态、混沌态以及倍周期分叉等现象的主要原因.     

Beat excitation of terahertz radiation in a semiconductor slab in a magnetic field

Two infrared lasers of frequencies ω₁ and ω₂ propagating in the TM/TE mode along $\stackrel{?}{z}$ direction in a rippled density semiconductor waveguide are shown to resonantly excite terahertz radiation at the beat frequency when ripple wave number is suitably chosen to satisfy the phase matching. The wave vector of the density ripple is along the direction of laser propagation while a static magnetic field is applied transverse to it. The lasers exert a ponderomotive force on the electrons at the beat frequency. This force, in the presence of density ripple and transverse magnetic field, produces a nonlinear current at the terahertz frequency. The magnetic field enhances the amplitude of the terahertz wave. However terahertz yield is significantly higher in the TM mode laser beating than in the TE mode laser beating.     

Space charge dynamics in a semiconductor superlattice affected by titled magnetic field and heating

The transition between different modes of current oscillations in a semiconductor superlattice, from close-to-harmonic (near the generation onset) to relaxation oscillations, has been investigated. The transition type is shown to change with an increase in temperature. A period-doubling bifurcation is observed at low temperatures. With an increase in temperature, the period-doubling bifurcation is observed at increasingly larger values of the voltage across the superlattice. The doubling bifurcation ceases to be observed at voltages at which the generation of oscillations of the current through the semiconductor superlattice is suppressed.     

The development of an electromotive force in a semiconductor placed in an inhomogeneous magnetic field

The possibility of development of an electromotive force (emf) in a semiconductor placed only in an inhomogeneous magnetic field is shown. The conditions and the experimental evidence of its appearance are presented.     

The second harmonic generation in semiconductors in the DC magnetic field

The second harmonic radiation in millimeter wave region is found in semiconductors in the absence of the dc electric field. The observed resonant maximum of radiation intensity is shown to be related to the excitation of the free-electron plasma oscillations in the dc magnetic field.     

The formation of the position-dependent band gaps in a semiconductor placed in the strong quantized inhomogeneous magnetic field

The influence of an inhomogeneous quantized magnetic field on the energy spectrum of a semiconductor is investigated. It is shown that the curvature and splitting of the energy levels of the conduction and valence bands lead to the appearance of the position-dependent band gaps.     

Analysis of the stability of states of semiconductor superlattice in the presence of tilted magnetic field

A method to calculate the spectrum of the Lyapunov exponents for a periodic semiconductor nanostructure (superlattice) described in the framework of a semiclassical approach is proposed. The analysis of the stability of a stationary state in such a system is performed for autonomous dynamics and in the presence of a tilted magnetic field. The method of the Lyapunov exponents is used to study the effect of the tilted magnetic field on the stability of the stationary state and the characteristics of subterahertz oscillation regimes.     

The effect of temperature on the nonlinear dynamics of charge in a semiconductor superlattice in the presence of a magnetic field

The space-time dynamics of electron domains in a semiconductor superlattice is studied in a tilted magnetic field with regard to the effect of temperature. It is shown that an increase in temperature substantially changes the space-time dynamics of the system. This leads to a decrease in the frequency and amplitude of oscillations of a current flowing through the semiconductor superlattice. The quenching of oscillations is observed, which is attributed to the change in the drift velocity as a function of electric-field strength under the variation of temperature.     

Magnetotransport in a semconductor superlattice with transverse magnetic field

Magnetotransport in a semiconductor superlattice (SL) under transverse magnetic field has been investigated. It is shown that in weak magnetic and electric fields there is negative magnetoresistivity along the SL layers and positive magnetoresistivity along the SL axis. The Hall resistivity is much less than the usual semiconductor value. With an increase of electric field, there appears a negative differential conductivity (NDC) along the SL layers, and the Hall voltage depends nonlinearly on current density. In higher electric field, destroying the miniband structure, the magnetoresistivity along the SL axis is negative. The magnetoresistivity along the SL axis in strong magnetic field is positive for any current density. The Hall resistivity in strong magnetic (electric) field equals the classical value.     

Electrodynamic response of a nanosphere placed in a magnetic field

Absorption of electromagnetic radiation by 2D electrons at the surface of a quantum sphere placed in a weak magnetic field is studied. It is shown that at low temperatures, the absorption curve exhibits four resonance peaks observed in the Faraday geometry (photon wave vector parallel to the magnetic field) and six peaks in the Voigt geometry (photon wave vector perpendicular to the magnetic field). In the particular case of the Voigt geometry, where the photon polarization vector is parallel to the magnetic field, the absorption curve exhibits only two resonance peaks. The shape, position, and intensity of the peaks are examined. It is shown that at temperatures close to zero, steps of two types appear in the absorption curve. One type of steps is associated with crossing of the μ-?ω level by the electron energy levels, while steps of the other type arise when electron energy levels cross the chemical potential μ.     

Soliton wall superlattice charge-density-wave phase in a magnetic field

A model where phase transitions between the Peierls and periodic soliton wall superlattice (SWS) charge-density-wave phases occur in a magnetic field is proposed. The model accounts for the peculiarities of the electron spectrum in a quasi-one-dimensional conductor (Per)₂Pt(mnt)₂. Possible experimental investigations of the theoretically predicted phase transitions in (Per)₂Pt(mnt)₂ to discover a unique SWS phase are discussed. The text was submitted by the authors in English.     

Three-dimensional harmonic oscillator in a magnetic field

A solution is found for the Schrödinger equation for a three-dimensional oscillator in a constant and uniform external magnetic field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 86–89, April, 1971.     

Nonlinear theory of the excitation of spin waves in ferrites by a longitudinal ultrahigh-frequency magnetic field

The problem of parametric excitation of spin waves in ferrites due to the action of a perturbing super high-frequency (SHF) magnetic field polarized along the direction of the constant magnetic field H₀ is considered in a nonlinear approximation. Such an examination enables one to determine the conditions for parametric excitation of spin waves and to find the amplitude and phase of the oscillations of the system's magnetization in the steady state. The frequency interval, within whose limits parametric excitation of spin waves is possible, is determined. Stability of the steady state under the conditions of parametric resonance is investigated. The results obtained are compared with existing experimental data.