Topological Insulators by Band-Gap Engineering

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Nontechnical description:Electrical insulators are commonly recognized as 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. In this project the principle investigator will perform experiments on the newly discovered topological insulators made of compound semiconductors indium arsenide and gallium antimonide, addressing important issues relate to materials science and quantum physics. Understanding of materials science of this class of material and their topological properties is directly relevant to spintronics and quantum information technology.Technical descripton:The two-dimensional topological insulator, which supports quantized helical edge modes, is created by band-gap engineering using molecular beam epitaxy and electrostatic gates. The project is exploring 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 are being systematically studied. Major focus of the study is searching for Majorana bound states in hybrid topological insulator-superconductor Josephson junctions. The experimental research work addresses fundamental phenomenon and its physics in a very clean model system. The project supports the education of two Ph.D. students, where they receive a combination of advanced training in semiconductor materials, nanotechnology, and ultra-low temperature measurements.