****Technical Abstract**** This research project will investigate spin, heat and charge transport in quantum Hall edge modes. Already in the integer quantum Hall regime once edge reconstruction occurs, correlated electron physics described by Luttinger liquid theory is needed in order to properly describe edge mode characteristics. In the fractional quantum Hall regime edge reconstruction is expected to produce both charged and neutral excitations that result from the interplay between confinement, Coulomb repulsion and disorder. A renewed interest in quantum Hall systems also arises due to the prospects of using such systems for topological quantum computing. Furthermore, in recent years, edge mode physics has also immerged in other material systems known as topological insulators even in the absence of an external magnetic field. Leading examples of intriguing edge mode physics in these systems are the quantized spin Hall effect and the anomalous quantized Hall insulator. Three approaches will be used in this project: cleaved edge overgrowth for sharp edges, laterally defined edges and suspended graphene. The experimental tools developed here for studying edge mode physics in the quantized Hall regime will offer new approaches for exploring edge mode physics in this new class of materials. This project will assess the possible technological use of topologically protected edge modes for dissipationless transfer of information in solid state devices. The research will be incorporated into our new graduate program that will be centered on the "fundamental properties of materials and their applications" as well as into our undergraduate curriculum addressing the "principles of scientific inquiry".
Microelectronic circuitry changed our lives. One of the growing challenges, however, in this field is the dissipation of energy or heat production due to the flow of electricity within such devices. These challenges call for new approaches for carrying information across microscopic dimensions. This project seeks to use other properties of electrons such as their intrinsic angular momentum, known as spin, as opposed to their charge, for carrying information. Electros move in circles when subject to an external magnetic field. In clean samples such circular motion prevents electricity from flowing in the bulk from one side of the sample to the other. However, near the boundaries of a sample this circular motion leads to skipping orbits which allow electrons to traverse the length of the sample without dissipation. In addition to their charge, electrons also carry spin and heat. Under unique conditions that result from the interactions between neighboring electrons, the edge modes at the boundary can carry heat and spin currents without carrying any charge current. Such neutral modes offer intriguing possibilities for carrying information without involving the charge of the carries. This project explores the properties of such edge modes in high purity semiconductors and will assess their utility in future applications. Participating students are trained in technological areas that are front and center in the nanoelectronics industry including nanofabrication, electrical measurement and data acquisition. Furthermore, by incorporating the research topics into the undergraduate and graduate curriculum, this project will prepare the next generation of scientists for future challenges in nanoelectronics and their applications.
