Electromagnetic renormalization of the plasmon spectrum in a laterally screened two-dimensional electron system

It is demonstrated theoretically that the effects of lateral electromagnetic screening of plasmons in a two-dimensional electron system by side metallic electrodes modify the plasmon spectrum. The effects of lateral screening become more pronounced at larger values of the plasmon wave vector. This leads to the deviation of the dispersion of laterally screened plasmons from the square-root dispersion law characteristic of unscreened plasmons. The results allow interpreting the recent experimental data of other authors on the dispersion of the plasma oscillations in a laterally screened two-dimensional electron system.     

Spectrum of plasma oscillations in structures with a periodically inhomogeneous two-dimensional electron plasma

We develop a rigorous electrodynamic theory of plasma oscillations in a periodically inhomogeneous two-dimensional electron system with a rectangular profile of the spatial modulation of the equilibrium electron concentration. We calculate the frequencies and radiative damping of the main plasma-oscillation types with a zero reduced wave vector. We show that the frequency splitting and the radiative damping of the oscillations are nonmonotonic functions of the modulation percentage and the ratio of the widths of the bands of two-dimensional plasma with low and high electron concentrations. The results of calculations are compared with experimental data and with the results of a perturbation theory developed in earlier work of other researchers. We discuss the physical mechanism for the emergence of radiative damping of plasma oscillations. Zh. éksp. Teor. Fiz. 113, 988–999 (March 1998)     

Polaronic effects in one-dimensional quantum antidot arrays

We study the effect of polaronic corrections arising from theelectron-longitudinal optical phonon interaction on the energyspectrum of a two-dimensional electron system with a one-dimensionalperiodic antidot array geometry created by a weak electrostaticmodulation potential, and subjected to a weak magnetic fieldmodulation as well as a uniform strong perpendicular staticmagnetic field. To incorporate the effects of electron-phononinteractions within the framework of Fröhlich polaron theory, wefirst apply a displaced-oscillator type unitary transformation todiagonalise the relevant Fröhlich Hamiltonian, and we thendetermine the parameters of this transformation together with theparameter included in the electronic trial wave function . On thebasis of this technique, it has been shown that the polaroniccorrections have non-negligible effects on the electronic spectrumof a two-dimensional electron system with a quantum antidot array,since switching such an interaction results in shifting thedegeneracy restoring points of Landau levels wherein the flatbandcondition is fulfilled, thus suppressing the Weiss oscillations.     

Study of the Cathode Sheath Dynamics After Arc Current Zero Crossing Using a Two-Dimensional Langmuir Probe System

Russian Physics Journal - A two-dimensional system of miniature Langmuir probes operating in the electron saturation current mode is proposed. With its help, the spatial distribution of plasma...     

Observation of plasmon-polariton modes in two-dimensional electron systems

A manifestation of retardation effects, which were predicted theoretically more than 35 years ago, is revealed for the first time in the plasma excitation spectrum of a two-dimensional electron system with a high electron mobility. It is shown that a significant decrease in the resonant plasma frequency due to a hybridization of the plasma and light modes is observed in zero magnetic field. An unusual dependence of the frequency of the hybrid cyclotron-plasmon mode on the magnetic field has been observed in a perpendicular magnetic field. The experimental results are in good quantitative agreement with the theory.     

基于自相似模型的二维X射线激光等离子体流体力学

从自相似方法出发,建立了简化的二维X射线激光等离子体流体动力学模型. 利用该模型研究了平板靶X射线激光的二维流体力学行为. 研究表明,当激光作用结束后,经过一段时间的演化电子密度和温度沿线聚焦方向逐渐达到平衡,该结果对X射线激光的优化设计具有重要意义. 关键词： X射线激光 二维流体力学计算 自相似方法     

Fermi Surface of a Quasi–Two-Dimensional Electron Gas

A model of the energy state of a quasi–two-dimensional electron gas is constructed based on a rectangular potential well of finite depth. The form of the Fermi surface and the character of its transformation from the true two-dimensional gas to the three-dimensional one are determined.     

Occurrence of a gap in the spectrum of magnetoplasma excitations of a two-dimensional electron disk subjected to a strong in-plane magnetic field

The effect of a parallel magnetic field on the dispersion of bulk and edge magnetoplasmons in a disk-shaped two-dimensional electron system is investigated. It is found that the anisotropy of the electron effective mass that appears in a parallel magnetic field lifts the degeneracy of plasma oscillations in the disk. This is accompanied by the occurrence of a gap in the spectrum of magnetoplasmons, and the magnetic dispersion of these excitations changes from a linear to a parabolic one. The width of the gap is determined by the difference between the frequencies of plasma oscillations along the field and transverse to the field and grows quadratically with the in-plane field strength.     

激光诱导环氧玻璃钢等离子体电子密度测量（英文）北大核心CSCD

利用马赫曾德尔干涉测量系统采集到等离子体的激光干涉图像。为了提高数据处理的精度,应用了改进的数字式二次曝光傅里叶法从干涉图中获取了初始的缠绕相位,并采用改进的基于掩膜与枝切法的相位解缠算法对缠绕相位进行相位解缠。在对解缠相位做Abel逆变换后,得到了不同延时时刻下激光诱导环氧玻璃钢等离子体电子密度的空间分布。结果显示:测量得到的电子密度主要为1018 cm~(-3)数量级。实验表明,在记录的时间范围内激光等离子体的电子总数变化不大,且电子密度的变化与等离子体体积的变化大致成反比。     

Plasma waves in a two-dimensional electron system laterally screened by a metallic gate

The dispersion of magnetoplasma and plasma excitations in two-dimensional electron systems, whose edges are formed by a voltage applied to a metallic gate, has been studied. A substantial decrease in the plasma wave frequency as compared to the plasma frequency measured in the etched mesas with the same geometry, size, and electron density has been observed. The dependence of the observed frequency softening on the structure size has been studied and the laterally screened plasma excitation has been shown to violate the square-root dispersion relation.     

Theory of resonant tunneling through quantum dots in the presence of electron-phonon interaction

Structures where the electrons of a two-dimensional electron gas are confined to disconnected regions can be fabricated by the use of appropriate gate geometries. The transport between these electrostatically defined quantum dots takes place by tunneling. Using the tunneling Hamiltonian approach we present a theoretical model of the system including electron-phonon interaction. The relevant coupling constants are determined from realistic wave functions for the expected confinement potentials. The phonon part of the Hamiltonian is diagonalized using a canonical transformation. Starting from the determination of the transmission matrix for the interacting system we calculate the current-voltage characteristics for different temperatures and phonon coupling strengths.     

Particle Simulation of Electrostatic Waves Driven by an Electron Beam

A one-dimensional electrostatic particle-in-cell simulation is performed to study electrostatic wave excitation due to an electron beam in a plasma system. The excited fundamental and harmonic waves are analyzed with the fast Fourier transformation and the wavelet transformation. The second harmonic is suggested to be generated by wave-wave coupling during the nonlinear evolution, which involves forward propagating and backward propagating Langmuir waves. Furthermore, the background electrons may be heated and accelerated by the electrostatic waves.     

针板型大气压氦气冷等离子体射流的二维模拟

大气压冷等离子体射流的传播机理一直是人们研究的一个热点. 本文采用自洽的二维等离子体流体模型, 研究了大气压氦气冷等离子体射流在自身环境气体中以及在介质管中的传播问题. 得到了电子密度、电离速率、空间电场以及电子温度等参量的时空分布规律, 分析了介质管大小以及介质管介电常数对射流放电性质的影响, 得到了一种提高电子密度和射流尺寸的新方法. 关键词： 大气压冷等离子体射流 等离子体子弹 数值模拟 流体模型     

Properties of the band gap of two-dimensional plasma photonic crystals

Employing the finite-difference time-domain (FDTD) method, we study the filtering properties of twodimensional plasma photonic crystals. We show that the transmission spectra of the defects in the plasma photonic crystals vary with change in the defect location, its radius, the plasma frequency, and the frequency of electron–ion collisions in the plasma. We demonstrate that the two-dimensional defect structure from the viewpoint of its frequency characteristic (such as an adjustable filter characteristic) is similar to the one-dimensional structure. We find that by changing the parameters of the defect location, the plasma frequency, and the frequency of electron–ion collisions in the plasma, one can obtain different ranges of transmission peaks at different frequencies, which fully reflects the adjustable filter characteristics of the structure. Therefore, the two-dimensional structure is more important than the one-dimensional structure, and it can be used to produce actual microwave devices.     

Comparative Study of the Two-Dimensional Plasma Excitations in the Heterostructures ZnO/MgZnO,AlAs/AlGaAs,and GaAs/AlGaAs

The plasma oscillations in new advanced two-dimensional electron systems (2DESs) based on the heterostructures ZnO/MgZnO, AlAs/AlGaAs, and GaAs/AlGaAs are studied and compared. The relaxation times and the effective masses in samples with various electron densities in these 2DESs are found by microwave plasma spectroscopy. The specific features of the plasma oscillations in the AlAs/AlGaAs quantum wells that are induced by the filling of several valleys with electrons are revealed. The possibility of adjusting a plasmon spectrum via changing the electron concentrations in valleys is demonstrated.     

Plasma oscillations in two-dimensional electron systems with a superstructure under Stark quantization conditions

The effect of quantizing electric field on plasma oscillations of two-dimensional electron gas in a system with a periodic potential has been theoretically investigated. The coupled-plasmon spectrum ω(q) is calculated for high temperatures (Δ ? T, where Δ is the conduction miniband width and T is temperature in energy units). The calculations are based on the quantum theory of plasma oscillations in the random-phase approximation, with allowance for the umklapp processes.     

电子关联与二维晶格的不稳定性

本文从电子相互作用的屏蔽库仑势出发,构造了Wannier函数来计算二维不稳定晶格的能带及电子波函数,用相关基函数理论计算了二维非均匀体系的电子关联函数,由此研究了电子关联对二维晶格不稳定性的影响。结果表明,二维体系与一维体系不同,电子相互作用使晶格二聚化减弱。 关键词：     

A convenient representation for describing an electron in a uniform magnetic field

The newly established single-complex-variable state vector set for the two-dimensional harmonic oscillator in Fock space is generalized to describe an electron moving in a uniform magnetic field. In this formulation, the related Feynman transformation matrix elements are easily derived.     

大面积等离子体片密度分布分析

利用空心阴极放电产生了尺寸为60 cm× 60 cm× 2 cm的大面积等离子体面. 在实验室条件下对大面积等离子体片的密度分布进行了测量. 由于高压放电脉冲脉宽较短, 实验中改变了测量方法, 同时, 在中等磁场影响下, 为了得到真实的等离子体密度, 进行了必要的数值修正.在放电电流为1---6 A时, 测量了二维的电子密度分布. 另外, 测量并讨论了其他环境参数对等离子体密度的影响. 电子密度的分布情况对与微波波束切换相当重要. 由空心阴极增强型放电产生的大面积等离子体面具有反射X波段(8---12 GHz) 微波需要的足够稠密的电子密度和足够均匀的密度分布, 这是等离子体面在雷达系统中取代金属面板的有利条件.     

Fluid turbulence in quantum plasmas

Nonlinear fluid simulations are developed by us to investigate the properties of fully developed two-dimensional (2D) electron fluid turbulence in a very dense Fermi (quantum) plasma. We find that a 2D quantum electron plasma exhibits dual cascades, in which the electron number density cascades towards smaller turbulent scales, while the electrostatic potential forms larger scale eddies. The characteristic turbulent spectrum associated with the nonlinear electron plasma oscillations (EPO) is determined critically by a ratio of the energy density of the EPOs and the electron kinetic energy density of quantum plasmas. The turbulent transport corresponding to the large-scale potential distribution is predominant in comparison with the small-scale electron number density variation, a result that is consistent with the classical diffusion theory.