Probing the Quantum Hall State by Electrically Detected ESR and ENDOR in GaAs and Si-MOSFET Heterostructures

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This individual investigator award will support a project to elucidate properties of correlated 2 dimensional electron systems (2DES) in the Quantum Hall regime. These studies will include: the measurement of the magnetization of the 2DES, the study of current induced dynamic nuclear polarization, and the role of spin in metal-insulator transitions in a Si-MOSFET 2DES. The experimental methods to be employed in the proposed investigations are electrically detected electron spin resonance and electrically detected electron-nuclear double resonance. Furthermore, a magnon model for the mechanism of the electrically detected electron spin resonance in the quantum Hall state will be developed and compared with the experimental temperature and microwave power dependence of the signal response. Experiments are to be conducted on high mobility GaAs/AlGaAs quantum wells fabricated at Sandia National Labs and Si-MOSFET heterostructure devices. Instrumentation at the National High Magnetic Field Laboratory and in the P.I.'s laboratory at the University of Florida will be employed to carry out the proposed investigations. Students involved with this research will gain skills that will prepare them for future careers in industry and academia. In addition, they will gain the experience of collaborating with scientists at national facilities.A fundamental understanding of the processes associated with the flow of electrons through composite semiconductor materials is key to the development of new types of devices with improved performance and novel characteristics. The "spin" of the electron plays a central role in the conductivity properties of high performance nanostructured semiconductors at low temperatures and high magnetic fields. Under these conditions (referred to as the quantum Hall regime), the flow of electrons is strongly affected by quantum mechanics where the available states of the electron are restricted to certain energies. This individual investigator award will support research aimed at probing the spin degree of freedom by resonance absorption of microwave energy. The spin of the electron can be "flipped" by this absorption, and as was first shown by the German Nobel Laureate Klaus von Klitzing, this can be detected as a change in the conductivity. This project will attempt to explain the mechanism of this electrically detected spin resonance effect, and to use it to probe the quantized energy levels in the nanostructured semiconductor. The research could impact on the development of "quantum computation" devices or new types of "spin transistors" with improved performance over conventional devices. The commercialization of these potential applications could have major long-term economic impact in the technology sector. Thus, representation in this research area by a US research group is crucial to the National interest. Students involved with this research will gain skills that will prepare them for future careers in industry and academia. In addition, they will gain the experience of collaborating with scientists at national facilities.