Spin and Pseudospin Degeneracies in Interacting Electron Systems

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9701958 Goldberg This experimental research project focuses on conducting systems formed by the "edge states" that lie near the perimeter of quasi- two dimensional electron gases in the quantum Hall effect (QHE). Fundamentally new transport behavior is predicted for sample geometries that bring multiple edge states into communication. Two sample geometries will be employed in this project. These are a GaAs/AlGaAs superlattice pillar with edge states communicating on a 2D surface sheath; and a gated GaAs/AlGaAs heterojunction with edge states communicating across a long, narrow "line gate" barrier. Existing theoretical predictions in these cases will be tested with measurements to be made using a high-field (19Tesla), low temperature (20mK) apparatus on samples fabricated from MBE-grown GaAs/AlGaAs heterostructures. It is expected that the results will advance general understanding of electronic transport in quasi-1D- and in anisotropic 3D- materials. %%% This research program examines ways in which electrons interact with each other to create ordered or collective structures. In many materials systems magnetism is driven by electronic interactions and in many technologically important areas like mass storage devices and computer memory, magnetism plays a fundamental role. Our program is an experimental effort to develop and examine model systems of magnetism. Only by using very pure model systems can the electronic interaction effects be isolated and studied. Our preliminary results have shown that when you have all electrons magnetically aligned, then forcing one to flip its orientation cause all its neighbors and their neighbors to turn to partially flip, creating a kind of swirl or vortex. These swirls of electrons, called Skyrmions, determine the magnetic properties of the material. To study Skyrmions, our group has built collaborations with Lucent Technology, the Kepler University in Austria, the Institute of High Pressure Physics in Russia, and the National High Magnetic Field Laboratory in Florida. The group encompasses students from high-school summer interns, to undergraduate and graduate students who will work together using novel techniques of light transmission to "see" these electron swirls and study their most fundamental properties. New microscopes are being developed, which will have eventual application in biology and DNA sequencing, extending beyond the materials science of this program. New materials systems combining silicon technology with optical properties will be used, which again will have application in future generations of optoelectronics. ***