Ballistic Transport in 2D Carrier Systems: Role of Spin and Valley Degrees of Freedom

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Spintronics is an emerging area in solid state science and engineering. Its broad goal is to utilize carriers, spin to realize novel electronic devices that rely on the creation, manipulation, and detection of spin and spin-currents. If successful, such manipulation of spins could also impact the even more exotic field of quantum computing, as spin is the leading candidate for registering the quantum bit of information in the proposed quantum computers. The goal of this project is to explore ballistic transport in clean, two-dimensional carrier systems in modulation-doped semiconductors. The project includes the fabrication and study of a number of devices whose operation relies on the manipulation of spin and/or valley degrees of freedom. The devices will be based on two different carrier systems: (1) two-dimensional hole system in GaAs quantum wells which possesses a strong and tunable spin-orbit interaction, and (2) two-dimensional electron system in AlAs quantum wells where the electrons occupy conduction band valleys with tunable densities, and have a large Lande effective g-factor so that the electrons can be easily spin-polarized. The project will involve crystal growth of the basic materials via molecular beam epitaxy, fabrication of various devices using modern lithography techniques, and transport measurements.Intellectual merit: The project will contribute to the fundamental understanding of the ballistic transport in semiconductor structures. Such knowledge is essential for advancements in the emerging fields of spintronics and quantum computing. It can also lead to the development of unforeseen device concepts. Broader impacts: The impact of the project will be seen in the scientific community and beyond. Results of the research will be communicated through publications and conference presentations to the specialized as well as general science and engineering communities, where the topic is generating substantial interest. Progress in this area will also benefit society in the long term as it may lead to novel electronic devices and information processing systems.The project incorporates a high quality and comprehensive educational component. It will result in the education of students in critical, state-of-the art areas of science and technology, including the fabrication, characterization, and physics of high quality layered semiconductor structures. Well-trained students in these fields will be invaluable resources for the US as well as for the rest of the world. The PI will also make every effort to attract to this project students from underrepresented groups.The PI is committed to a broader education of the public in science and engineering. Some of the topics and results of this project will be incorporated into undergraduate and graduate courses that he teaches at Princeton University. The PI will also participate in various K-12 demonstrations and teacher training programs in electricity and magnetism, general areas that are closely linked to the topic of this proposal. These activities include training sessions, kit development, and demonstrations at regional school, and at Princeton University.