Thermodynamic and Transport Studies of Strongly Interacting Electrons in Two-Dimensional Semiconductors

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This project will investigate the interplay between strong Coulomb interactions and random electrostatic potentials, one of the central problems in condensed matter physics. It is well known that in two-dimensional systems of non-interacting or weakly interacting electrons, the ever-present random environment leads to an insulating ground state. However, new evidence has emerged within the past decade that indicates a transition from a an insulating to a metallic phase in two-dimensional systems of strongly interacting electrons, with anomalous magnetic properties reported near the transition. These results have inspired numerous experimental and theoretical studies. The current project will focus on measurements of the thermodynamic quantities of "just metallic" two-dimensional electron and hole systems. Specifically, orbital and spin magnetization of strongly interacting electrons (holes) will be studied using a newly developed technique. The experiments will be carried out in ultra-clean silicon MOSFETs, as well as in other low-disordered two-dimensional systems: p- and n-type SiGe heterostructures. These experiments will be accompanied with sensitive ultra-low temperature transport measurements, such as parallel magnetoresistance and Shubnikov-de Haas measurements. It is expected that the results will add significantly to our understanding of the metal-insulator transition in two dimensions. Another impact will be on education, as this project will provide students an excellent introduction to research in forefront area physics. It will incorporate Northeastern's well-known "co-op" education program for undergraduates.The interplay between strong Coulomb interactions and random potentials has been a long-standing problem in condensed matter physics. New evidence has emerged within the past decade indicating that at ultra-low temperatures, strong interactions between electrons may stabilize a metallic state in two-dimensional systems. These results have attracted great attention in the scientific community and have inspired significant experimental and theoretical activity. The proposed research is a continuing experimental effort to understand this important problem. The results anticipated from the proposed experiments will advance basic knowledge, and may have impacts on the development of next generation semiconductor devices for high-speed communications, signal processing, imaging, and detection. For example, the new technological areas such as semiconductor-based quantum computation and spintronics are known to depend heavily on this kind of knowledge. Another impact will be on education, as this project will provide an excellent introduction for students to carry out research at the forefront of physics. The project will give graduate and undergraduate students an excellent preparation for careers in academe, industry, and government.