Coupled Plasmons and Single Particle Excitations in the Two-Dimensional Electron Gas
Coupled Plasmons and Single Particle Excitations in the Two-Dimensional Electron Gas
复制标题
二维电子气中的耦合等离子体和单粒子激发
DOI：
--
复制
发表时间：
1987
期刊：
影响因子：
--
通讯作者：
K. Ploog
中科院分区：
文献类型：
--
作者：
Gerhard Fasol;N. Mestres;A. Fischer;K. Ploog
与调制掺杂异质结和多量子阱的二维电子层平行的载流子的运动、激发和介电响应的特征在于集体激发（密度振荡=等离子体激元）和单粒子激发（单电子的加速）。这些激发对应于自旋密度和电荷密度波动。它们确定层状电子系统对电磁场的响应，例如库仑相互作用的筛选，例如杂质或传导过程。我们通过实验证明，具有 N 层的层状电子系统具有 N 个离散等离子体本征模式。测量这些模式提供了一种研究系统中一系列相互作用的方法：层之间的库仑相互作用，以及等离子体激元与其他激发的相互作用。由于不同层中电子之间的库仑相互作用，离散层等离子体激元模式扇出成带。我们测量了离散层等离子体本征模式的色散作为面内波矢量 k|| 的函数。用于具有少量层数的调制掺杂 GaAs/AlGaAs 量子阱 (N = 2...20)。这些测量可以测试层状系统中等离子体色散的大量理论计算。他们还提供了一种表征层状电子气系统中电子密度的技术。因此，3D 等离子体频率的测量目前用于确定掺杂体半导体中的载流子浓度。我们测量了单粒子激发 (SPE) 光谱的波矢和温度依赖性。 SPE 谱可以通过 Lindhard-Mermin 介电响应函数很好地拟合，并且我们确定了样品的单粒子弛豫时间的温度依赖性。
The motion, the excitations and the dielectric response of carriers parallel to the two-dimensional electron layers of modulation doped heterojunctions and multi-quantum wells are characterised by collective excitations (density oscillations = plasmons) and single particle excitations (acceleration of single electrons). These excitations correspond to spin density and charge density fluctuations. They determine the response of layered electron systems to electromagnetic fields, such as screening of the Coulomb interaction, e.g., of impurities, or the conduction processes. We show experimentally, that a layered electron system with N layers has N discrete plasmon eigenmodes. Measuring these modes provides a method to study a range of interactions in the system: the Coulomb interaction between layers, and interaction of the plasmons with other excitations. The discrete layer plasmon modes fan out into a band due to the Coulomb interaction between electrons in different layers. We have measured the dispersion of the discrete layer plasmon eigenmodes as a function of the in-plane wave vector k|| for modulation doped GaAs/AlGaAs quantum wells with a small number of layers (N = 2... 20). These measurements allow to test the large number of theoretical calculations of the plasmon dispersion in layered systems. They also provide a technique to characterise electron densities in layered electron gas systems. Thus measurement of the 3D plasmon frequency is currently used to determine the carrier concentration in doped bulk semiconductors. We have measured the wavevector and temperature dependence of the single particle excitation (SPE) spectra. The SPE spectra can be well fitted by a Lindhard-Mermin dielectric response function, and we determine the temperature dependence of the single particle relaxation time for our sample.