Optical Studies of Tunneling and Coulomb Correlations in Mixed-Type Quantum Wells

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****Technical abstract****This project will investigate electron-hole bilayers formed in semiconductor quantum well structures, in which electrons and holes reside respectively in wide and narrow wells separated by a thin barrier. A special feature of this structure is that the carrier density can be controlled via optical excitations of the narrow quantum well. Two closely related research directions will be pursued. The first direction explores how manybody Coulomb correlations between electrons and holes across the barrier affect carrier tunneling. The correlation-induced tunneling will also be exploited as a new mechanism for excitonic nonlinear optics. The second direction aims to engineer an array of localized holes, realizing a system where two-dimensional electrons interact in the presence of the electrostatic potential of a hole lattice. A near term goal is to use this tunable semiconductor system to explore and possibly simulate strongly-correlated phenomena such as Mott insulators. This project will support the education of two graduate students in areas of both scientific and technological importance. This training will prepare the students for careers in academia, industry, or government. ****Non-technical abstract****Tunneling of electrons across a barrier in a semiconductor is an interesting quantum mechanical process and serves important roles in many electronic devices. Tunneling is traditionally viewed as a process involving single electrons. This project explores phenomena in semiconductor nanostructures where tunneling processes can depend strongly on interactions or correlations between electrons across the tunneling barrier. This correlation-induced tunneling process will be exploited for applications such as photonic switching devices. Effects of correlations between electrons also play important roles in understanding a variety of fascinating physical phenomena such as high Tc superconductors and magnetism. A second and closely related research direction of this project is to develop a system, in which electrons in a two-dimensional semiconductor structure interact in the presence of a periodic array of positively-charged holes. This system can be used to vary or tailor effects of electron correlations, serving as a platform for investigating and understanding effects of electron correlations in condensed matter systems. This project will primarily be carried out by two graduate students. The research activities will provide these students solid training in areas of both scientific and technological importance, preparing the students for careers in academia, industry, or government.