Plasma Oscillations in an Inhomogeneous Electron Gas

非均匀电子气中的等离子体振荡

• 批准号: 9314899
• 负责人: Elisabeth Gwinn
• 金额: --
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-02-15 至 1998-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9314899&HistoricalAwards=false
• 关键词: Plasma; Oscillations; Inhomogeneous; Electron; Gas

9314899 Gwinn The dynamical response of quasi-3D electron gases will be probed using linear and nonlinear techniques. These types of electron gases are of fundamental interest since they exhibit metallic behavior (rs~2.5) but at much reduced plasma energies (~4 meV) compared to typical metals. The materials are molecular beam epitaxially grown AlxGa1-xAs superlattice structures which are specially designed to yield a 3D electron gas with widths which are less than several Fermi wavelengths (hence quasi-3D). The electronic ground state of the electron gas will be probed using low temperature capacitive profiling and Shubnikov-de-Haas oscillations. The linear studies, using standard Fourier transform spectroscopic techniques, will expand the understanding of the interplay between the excitation of the electron gas and the spatial variation of its ground state density. Proposed density variations include internal gradients, as in the bi-metallic gas, near surface perturbations, and lateral modulations induced by optical illumination through a grating. The nonlinear studies will be carried out using an intense tunable far infrared free-electron laser source. The experiment will measure the harmonic emission generated by the quasi-3D electron gas for frequencies above as well as below the plasma frequency. Modeling of this emission will yield information about nonlinear dynamic screening in an inhomogeneous electron gas. %%% Layered semiconductors can be grown by molecular beam epitaxy to provide electronic systems which are models for a three dimensional gas of free electrons. Because of its finite lateral dimension such a structure is referred to as a quasi-free dimensional electron gas. Proper growth control can establish an inhomogeneous distribution of electrons. Study of the response of such inhomogeneous quasi-3D electronic distributions to low level and high intensity radiation is proposed. The angular frequency of the radiation is comparable to t he fundamental electronic response frequency of the electron gas (plasma frequency). The expected measurements will likely lead to an improved understanding of the dynamic surface response of free electron materials, and be important for the development of tunable electronic materials that take advantage of the high degree of control over the electron density that can be achieved within these semiconductor structures. ***

拟三维电子气体的动力学响应将采用线性和非线性技术进行研究。这些类型的电子气体具有基本的兴趣，因为它们表现出金属行为（rs~2.5），但与典型金属相比，等离子体能量（~4 meV）大大降低。材料是分子束外延生长的AlxGa1-xAs超晶格结构，专门设计用于产生宽度小于几个费米波长的3D电子气体（因此是准3D）。利用低温电容谱和舒布尼科夫-德-哈斯振荡来探测电子气体的电子基态。线性研究，使用标准傅里叶变换光谱技术，将扩大对电子气体的激发和其基态密度的空间变化之间相互作用的理解。提出的密度变化包括内部梯度，如在双金属气体中，近表面扰动，以及通过光栅的光学照明引起的横向调制。非线性研究将使用强可调谐远红外自由电子激光源进行。实验将测量准三维电子气体在等离子体频率以上和以下频率下产生的谐波发射。这种发射的建模将得到关于非均匀电子气体中非线性动态屏蔽的信息。层状半导体可以通过分子束外延生长，提供三维自由电子气体模型的电子系统。由于其有限的横向维数，这种结构被称为准自由维电子气体。适当的生长控制可以建立电子的非均匀分布。提出了这种非均匀准三维电子分布对低强度和高强度辐射的响应研究。辐射的角频率与电子气体的基本电子响应频率（等离子体频率）相当。预期的测量结果可能会导致对自由电子材料动态表面响应的更好理解，并且对于开发可调电子材料非常重要，这些可调电子材料利用了在这些半导体结构中可以实现的对电子密度的高度控制。＊＊＊