Topological Insulators by Band-Gap Engineering

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****Technical Abstract****This project will pursue experiments on the novel properties of newly discovered topological insulators made of compound semiconductors indium arsenide and gallium antimonide. This two-dimensional quantum spin Hall insulator, which supports quantized helical edge modes, is created by band-gap engineering using molecular beam epitaxy and electrostatic gates. The project will continue to explore interesting physics at the messoscopic length scale, with the focus on the helical edge modes and their interface with superconductors, where proximity effect and Andreev reflection will be systematically studied. The project will support the education of two Ph. D students, where a combination of advanced trainings in semiconductor materials, nanotechnology, and ultralow temperature measurements will be received. Understanding of materials science of this class of material and their topological properties is directly relevant to spintronics and quantum information technology. ****Non-Technical Abstract****Electrical insulators commonly refer to the materials that prevent the flow of electricity. However, recent research demonstrates a type of topological insulators which has novel properties. Although electricity cannot flow through them, it can flow around their narrow outer edges. The material, called a "quantum spin Hall topological insulator", acts as an electron superhighway. It is one of the building blocks needed to create future electronics and computers. This project will pursue experiments on the newly discovered topological insulators made of semiconductors indium arsenide and gallium antimonide, addressing important issues relate to materials science and quantum physics. This will be accomplished using the most advanced tools of nanotechnology and ultralow temperature measurements. The project will support the education of two Ph. D students in semiconductor materials and technology, as well as fundamental physics.