Reflection and absorption of light by a quantum well in a strong magnetic field under pulsed irradiation

The interaction between a quantum well with a large number of equidistant excited electron energy levels and light is investigated. It is shown that nonsinusoidal oscillations occur in the transmitted, reflected, and absorbed energy fluxes under exposure of the quantum well to irradiation with light pulses. For long pulses whose length γ _l ^?1 is one order of magnitude longer than the time ?/ΔE (where ΔE is the energy level spacing), the oscillation amplitude is small. In the case of narrow pulses when γ _l ^?1 ≤?/ΔE, the oscillation amplitude is comparable to the flux magnitudes. For very narrow pulses with

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, the decaying echo of exciting pulse should be observed at the time intervals 2π?/ΔE. Symmetric and asymmetric pulses are considered. The theory is applicable to narrow quantum wells in a strong magnetic field when the equidistant levels correspond to electron-hole pairs with different Landau quantum numbers.

     

Activation of a semiconductor surface by a pulsed magnetic field

The possibility of semiconductor surface activation, which shows up as a long-term increase in the adsorption capacity in response to a short exposure to a pulsed magnetic field, is demonstrated for the first time. Magnetic-field-induced surface activation is studied on silicon, germanium, and gallium arsenide crystals. The effect revealed extends the capabilities of thin-film growth on the semiconductor surface.     

脉冲磁场下水热法制备Cr掺杂ZnO稀磁 半导体晶体

本文以ZnCl₂, CrCl₃. 6H₂O和氨水缓冲溶液为原料, 在4T脉冲磁场下水热法制备了Cr掺杂ZnO稀磁半导体晶体, 通过X射线衍射分析、扫描电子显微镜观察及采用振动样品磁强计进行磁性分析等, 探讨了脉冲磁场对其微观结构及磁性能的影响. 结果表明: Cr掺杂ZnO稀磁半导体晶体仍保持ZnO的六方纤锌矿结构, 脉冲磁场具有促进晶粒生长及取向排列的作用, 4T脉冲磁场条件下合成的Cr掺杂ZnO稀磁半导体具有良好的室温铁磁性, 其饱和磁化强度(M_s)为0.068 emu/g, 而无脉冲磁场情况下制备的样品室温下呈顺磁性, 并且, 脉冲磁场下制备将稀磁半导体的居里温度提高了16 K.     

Interband light absorption by a semiconductor in a pulsing electric field

The light absorption by a semiconductor, placed in a pulsing electric field of arbitrary amplitude and pulse duration is considered. The calculation of the absorption coefficient is carried out on the ground of the effective mass method for direct optical transitions between two simple parabolic bands. The calculated absorption coefficient is valid for photon energies both greater and lesser than the semiconductor forbidden bandwidth.     

Electronic states and interband light absorption in semi-spherical quantum dot under the influence of strong magnetic field

In the framework of effective mass approximation the electronic states in semi-spherical quantum lens under the influence of strong magnetic field are investigated. We have used the adiabatic approximation for the case of strong magnetic field. The eigenfunctions and eigenvalues of this problem are determined. In strong confinement regime interband optical absorption of light is investigated in quantum lens from InAs. The threshold frequencies of absorption are determined. The comparison with the case of film under the influence of strong magnetic field with infinitely high confinement potential is performed.     

Intersubband collective excitations in quasi-two-dimensional systems in a strong magnetic field

The spectrum of intersubband collective excitations of spin and charge density in a system of quasi-two-dimensional electrons is calculated in the strong magnetic field limit for filling factors υ≤4. For υ≤2 two new closely spaced modes of collective excitations are obtained. The modes obtained make it possible to give a new interpretation of the experimentally observed line, which is usually interpreted as being due to single-particle excitations. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 8, 543–547 (25 April 1999)     

Collective excitations of a layered electron gas in a strong magnetic field

We determine the excitations of a layered electron gas in a strong magnetic field calculating the density-density response function, the transverse dynamical spin susceptibility and the phonon propagator by means of a Green's function technique. Electron tunneling processes between adjacent planes are taken into and found to be important for our results. In the limita/d1 (wherea is the magnetic length andd the distance between neighbouring planes) a very simple expression for the dynamical local field correction is found allowing us the evaluation of dispersion relations for magneto-plasmon, magneto-magnon and magneto-phonon in a straightforward manner. The transition temperature for a Magneto-Peierls transition is determined in dependence on electron-phonon coupling matrix element, tunneling probability, magnetic length and interplane distance.     

Electron states and light absorption in a thin ellipsoidal quantum lens in the presence of a strong magnetic field

Within the framework of adiabatic approximation the energy levels and direct interband light absorption in a thin ellipsoidal quantum lens in the presence of a magnetic field are studied. Analytical expressions for the particle energy spectrum and for the absorption threshold frequencies in the regime of strong size quantization for the cases of ellipsoidal and spherical cross-section segments are obtained. Selection rules for quantum transitions are revealed.     

Thermopower of a semiconductor film with parabolic potential in a strong magnetic field

Relationships for the transverse magnetothermopower of a semiconductor film with parabolic potential are derived for the cases of nondegenerate statistics and strong degeneracy. It is demonstrated that, in the case of strong degeneracy, quantum levels lying below the Fermi level intersect the Fermi level with an increase in the magnetic field, which leads to jumpwise oscillations of the thermopower magnitude.     

射频场控制的磁子能级中单色激光吸收抑制

理论上研究了射频场作用下多塞曼能级系统中单色激光的吸收抑制现象.一束单色线偏振或者椭圆偏振的激光作用于铷原子两能级间,线或椭圆偏振矢量方向与磁场方向垂直.在磁场中冷铷原子能级发生分裂,通过一个射频场将这些磁子能级耦合起来.当扫描射频场频率时,计算表明原子对单色光的吸收谱中出现了透射峰,类似于电磁诱导透明现象,光吸收减弱,光场透射增强.对于线性偏振或者椭圆偏振的单色光均能得到透射增强的结果.这种现象完全不同于通常光泵磁共振实验中射频场与磁子能级谐振时光被吸收最多的现象.这种扫描射频场频率时单色光的透射增强现象来自于磁子能级间的相干效应.计算表明在扫描射频场频率时单色光吸收谱中出现的透射峰与射频场的拉比频率和椭圆偏振光的左旋和右旋圆偏振成分相关.这种射频场控制的单色光透射增强效应在磁场测量,光信息处理等领域有潜在的应用价值.     

射频场控制的磁子能级中单色激光吸收抑制

理论上研究了射频场作用下多塞曼能级系统中单色激光的吸收抑制现象.一束单色线偏振或者椭圆偏振的激光作用于铷原子两能级间,线或椭圆偏振矢量方向与磁场方向垂直.在磁场中冷铷原子能级发生分裂,通过一个射频场将这些磁子能级耦合起来.当扫描射频场频率时,计算表明原子对单色光的吸收谱中出现了透射峰,类似于电磁诱导透明现象,光吸收减弱,光场透射增强.对于线性偏振或者椭圆偏振的单色光均能得到透射增强的结果 .这种现象完全不同于通常光泵磁共振实验中射频场与磁子能级谐振时光被吸收最多的现象.这种扫描射频场频率时单色光的透射增强现象来自于磁子能级间的相干效应.计算表明在扫描射频场频率时单色光吸收谱中出现的透射峰与射频场的拉比频率和椭圆偏振光的左旋和右旋圆偏振成分相关.这种射频场控制的单色光透射增强效应在磁场测量,光信息处理等领域有潜在的应用价值.     

Theory of hopping conduction in two-dimensional impurity band under strong magnetic field

It is shown that the low-temperature conductivity in two-dimensional impurity band of n-type inversion layer under strong magnetic field is $\text{σ}{}_{\mathrm{xx}}\text{(}\text{min}\text{)=σ}{}_0\text{exp}\text{[?(}\text{T}{}_0\text{T}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{]}$. Therefore the effective conductivity of inversion layer $\text{σ}{}_{\mathrm{<mtext>eff</mtext>}}\text{=}\text{σ}{}^2{}_{\mathrm{xy}}\text{σ}{}_{\mathrm{xx}}\text{(}\text{min}\text{)}$ at Shubnikov-de Haas conductivity minima may be very high at low temperature.     

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.     

Interaction of classical nonrelativistic identically charged particles in a strong pulsed light field

In this review we consider the effective interaction force of identically charged nonrelativistic particles (electrons, light and heavy atoms nuclei) in a strong pulsed laser field. It is shown that under certain conditions, the effective interaction force can become a force of attraction. This effect significantly changes the kinematics of the interaction between the particles and can lead to bound states.     

High energy neutrino absorption by W production in a strong magnetic field

An influence of a strong external magnetic field on the neutrino self-energy operator is investigated. The width of the neutrino decay into the electron and W boson, and the mean free path of an ultra-high energy neutrino in a strong magnetic field are calculated. A kind of energy cutoff for neutrinos propagating in a strong field is defined.     

脉冲磁场对水热法制备Mn掺杂ZnO稀磁半导体的影响

本文以Zn(CH₃COO)₂·2H₂O, Mn(CH₃COO)₂·4H₂O和氨水缓冲溶液为原料, 在4 T脉冲磁场下利用水热法制备了Mn掺杂ZnO稀磁半导体晶体, 通过X射线衍射、 扫描电子显微镜、透射电子显微镜、拉曼光谱、荧光分光光度计及振动样品磁强计等对样品的微观结构及磁性能等进行了表征, 结果表明: Mn掺杂ZnO稀磁半导体晶体仍保持ZnO六方纤锌矿结构, 4 T脉冲磁场下合成的Mn掺杂ZnO稀磁半导体晶体具有明显的室温铁磁性, 其饱和磁化强度(M_s)为0.028 emu/g, 比无脉冲磁场下制备的样品提高一倍以上, 且4 T 脉冲磁场将样品的居里温度提高了15 K.     

Reflection and absorption of light by a thin semiconductor film

Optics and Spectroscopy - Reflection and absorption of light by a thin semiconductor film are investigated using the local field method taking into account local field inhomogeneities. The...