High-Sensitivity Thermodynamic Measurements of Interacting Disordered Quantum Hall Systems

这个实验凝聚态物理项目涉及相互作用的无序半导体异质结构的高灵敏度热力学测量。热力学测量提供了这些器件的多体基态性质的探针。具体地说，计划进行两项高灵敏度测量。首先，将使用低温扫描隧道显微镜绘制出二维电子层的热力学可压缩性的空间分布。其次，将使用扭转磁强计测量强相互作用空穴装置的轨道和自旋磁化强度。重点将放在无序如何在数量上和质量上改变多体基态性质上。一些悬而未决的问题将被解决，涉及零磁场下二维绝缘态和金属态的性质，这些相随着磁场的增加而向量子霍尔态的演化，以及具有无序的相互作用系统的自旋态。这些实验的预期结果有望更好地理解无序对相关低维半导体器件的影响。这些先进的基础知识应该会对用于高速通信、信号处理、成像和检测的下一代半导体设备的开发产生更广泛的影响。例如，基于半导体的量子计算、量子通信和自旋电子学等新技术领域都严重依赖于这种知识基础。此外，本研究开发的高灵敏度测量技术还可以用于半导体器件以外的领域。利用这些技术工具，可以潜在地研究小规模凝聚态材料板谱的热力学性质。最后，实践研究将为研究生和本科生在学术界、工业界和政府的职业生涯做好极好的准备。这项实验凝聚态物理涉及半导体异质结构的高灵敏度热力学测量。这些器件与信息处理中高速电子设备上广泛使用的器件非常相似。与更传统的电学测量不同，热力学测量提供了了解这些电子设备的基本能量配置的方法。将进行两个具体的实验。低温扫描隧道显微镜将被用来绘制出电子设备的局部电可压缩性。一层电荷载流子的微小磁化强度将由超灵敏的扭转磁强计测量。这些实验的预期结果有望引导人们对这些半导体器件的物理学有基本的见解；特别是传统的输运测量无法回答的基本问题。这些基本知识应该会对用于高速通信、信号处理、成像和检测的下一代半导体设备产生影响。例如，基于半导体的量子计算、量子通信和自旋电子学等新技术领域都严重依赖于这种知识基础。此外，本研究开发的高灵敏度测量技术还可以用于半导体器件以外的领域。利用这些技术工具，可以潜在地研究小规模凝聚态材料板谱的热力学性质。这些实践研究将为相关的研究生和本科生为在学术界、工业界和政府部门就业做好准备。

This experimental condensed matter physics project involves high-sensitivity thermodynamic measurements of interacting disordered semiconductor heterostructures. The thermodynamic measurements provide probes the many-body ground state properties of these devices. Specifically, two high sensitivity measurements are planned. First, spatial distribution of the thermodynamic compressibility of a two-dimensional electron layer will be mapped out using a cryogenic scanning tunneling microscope. Second, orbital and spin magnetization of a strongly interacting hole device will be measured using a torsion magnetometer. Emphasis will be on how the disorder can quantitatively and qualitatively alter the many-body ground state properties. Several outstanding questions will be addressed concerning the nature of the insulating and the metallic states in two-dimensions at zero magnetic field, the evolution of these phases to the quantum Hall states as the magnetic field is increased, and the spin states of an interacting system with disorders. The results anticipated from these experiments are expected to provide a better understanding of the effects of disorder on correlated low-dimensional semiconductor devices. This advanced basic knowledge should have broader impacts on the development of the next generation of semiconductor devices for high-speed communications, signal processing, imaging, and detection. For example, the new technological areas such as semiconductor-based quantum computation, quantum communications, and spintronics are known to depend heavily on this kind of knowledge basis. In addition, the high sensitivity measurement techniques developed in this research can be used beyond the semiconductor devices. Thermodynamic properties of a board spectrum of small-scale condensed matter materials can be potentially studied with these technical tools. Finally, the hands-on research will give graduate students as well as undergraduate students an excellent preparation for careers in academe, industry, and government.This experimental condensed matter physics involves high-sensitivity thermodynamic measurements of semiconductor heterostructures. These devices are very similar to those widely used on high-speed electronics in information processing. Unlike the more conventional electrical measurements, the thermodynamic measurements provide means to understand the fundamental energy configuration of these electronic devices. Two specific experiments will be conducted. A low-temperature scanning tunneling microscope will be used to map out the local electrical compressibility of an electron device. The tiny magnetization of a layer of charge carriers will be measured by an ultra-sensitive torsion magnetometer. The results anticipated from these experiments are expected to lead fundamental insights in the physics of these semiconductor devices; particularly the basic questions that cannot be answered by the conventional transport measurements. This basic knowledge should have impact on next generation of semiconductor devices for high-speed communications, signal processing, imaging, and detection. For example, the new technological areas such as semiconductor-based quantum computation, quantum communications, and spintronics are known to depend heavily on this kind of knowledge basis. In addition, the high sensitivity measurement techniques developed in this research can be used beyond the semiconductor devices. Thermodynamic properties of a board spectrum of small-scale condensed matter materials can be potentially studied with these technical tools. The hands-on research will give involved graduate students as well as undergraduate students an excellent preparation for careers in academe, industry, and government.