Collaborative Research: Study of Novel Phases in Two Dimensional Electron Systems in High Magnetic Fields and Low Temperature

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This Collaborative Research Project will continue experiments that may be evidence for a metal-insulator (M-I) transition in two-dimensional systems of electrons in semiconductors. The M-I transtion has been thought by many to be forbidden on general theoretical grounds. The data, which are suggestive of a M-I transition, remains a mystery despite a growing number of theoretical and experimental papers on the subject. Important recent progress, made by two experimental groups involved in the present project, has shown that the M-I transition in silicon inversion layers may be connected with a ferromagnetic instability in two dimensions. To test this intriguing possibility, magnetoresistance measurements will be performed at ultra-low temperatures and high magnetic fields at the MicroKelvin facility of the NSF-supported National High Magnetic Field Laboratory at Gainesville, Florida. The information sought will be crucial for the understanding of the nature of the enigmatic behavior observed in the two-dimensional electron gas systems. Graduate and undergraduate students participating in this project will receive training in a complex and important area of forefront physics involving cutting edge technology and semiconductor device structures. This will prepare them for a range of careers in industry, government or education.This Collaborative Research Project will investigate the properties of very high purity semiconductor materials in a MOSFET structure somewhat related to those found in many current electronic devices. Contrary to the widely-held expectation that no metallic phase is possible in such two dimensional semiconductors, experimental evidence has been obtained in the last few years that indicates there may be a transition from insulating to metallic behavior. The issue remains unresolved despite a growing number of theoretical and experimental papers on the subject, and poses a serious challenge to our understanding of the behavior of electrons in semiconductors. The principal investigators of the present project have been leading contributors to this field, and have independently obtained recent evidence that the metal-insulator transition may be associated with a tendency toward a ferromagnetic transition. To test this intriguing possibility, measurements will be performed at ultra-low temperatures and high magnetic fields at the MicroKelvin facility at NSF-supported National High Magnetic Field Laboratory at Gainesville, Florida. Gainesville, Florida. The information obtained is expected to be crucial for the understanding of the nature of the enigmatic behavior observed in two dimensional semiconductors. Graduate and undergraduate students participating in this project, including some minority students, will receive training in a complex and important area of forefront physics involving cutting edge technology, including semiconductor device structures This will prepare them for a range of careers in industry, government or education.