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。热力学测量提供探针这些器件的多体基态性质。具体来说，计划进行两次高灵敏度测量。首先，利用低温扫描隧道显微镜绘制二维电子层热力学可压缩性的空间分布。其次，利用扭转磁强计测量强相互作用空穴器件的轨道和自旋磁化强度。重点将放在失序如何定量和定性地改变多体基态性质。本文将讨论在零磁场下二维绝缘态和金属态的性质、随着磁场的增加这些相向量子霍尔态的演化以及与无序相互作用系统的自旋态等几个突出问题。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。这种先进的基础知识应该对下一代高速通信，信号处理，成像和检测半导体器件的发展产生更广泛的影响。例如，以半导体为基础的量子计算、量子通信和自旋电子学等新技术领域都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可以应用于半导体器件以外的领域。这些技术工具可以潜在地研究小型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准备。这个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。这些设备与在信息处理中广泛使用的高速电子设备非常相似。与更传统的电测量不同，热力学测量提供了理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用于绘制电子器件的局部电压缩性。一层载流子的微小磁化将由超灵敏的扭转磁力计测量。这些实验的预期结果有望为这些半导体器件的物理学提供基本见解；特别是传统输运测量无法回答的基本问题。这些基本知识将对下一代高速通信、信号处理、成像和检测的半导体器件产生影响。例如，以半导体为基础的量子计算、量子通信和自旋电子学等新技术领域都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可以应用于半导体器件以外的领域。这些技术工具可以潜在地研究小型凝聚态材料板谱的热力学性质。实践研究将为参与的研究生和本科生在学术界、工业界和政府的职业生涯做好充分的准备。

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.