Toward Spin- and Valleytronic Devices

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Spintronics and, more recently, valleytronics, are emerging areas in solid state science and engineering that utilizes carriers' spin/valley degrees of freedom to realize novel electronic devices that rely on the creation, manipulation, and detection of spin/valley currents. Such manipulation is expected to impact the field of quantum computing, as spin/valley are candidates for registering the quantum bit of information in quantum computers. The focus of the projects proposed here is to study ballistic transport in clean carrier systems in layered semiconductor structures. The goal is to demonstrate and characterize a number of electronic devices such as spin-interference device, spin-filter, and valley-filter, whose operation relies on the manipulation of spin and/or valley degrees of freedom. The project incorporates a comprehensive educational component, including graduate and undergraduate students training and curriculum development. Outreach activities involve developing demonstration kits for K-12 students in New Jersey schools, for public libraries and for teachers training programs at Princeton University. The main goal of the proposed projects is to demonstrate and characterize a number of electronic devices whose operation relies on the manipulation of spin and/or valley degrees of freedom. These include a spin-interference device, a spin-filter, and a valley-filter. The devices will be based mainly 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) 2D electron system in AlAs quantum wells where the electrons occupy conduction band valleys with tunable densities, and also have a large Lande effective g-factor so that they can be easily spin-polarized. The projects will involve fabrication of various devices using modern crystal growth and lithography techniques, and transport measurements. The projects 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/or valleytronics and quantum computing.