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.
