The past decade has seen a phenomenal rise of topological insulators and superconductors. The first discovery, led by the Stanford group and the Wurzburg group, concerns a planar material of a "quantum spin Hall topological insulator," which acts as an electronic superhighway. It is one of the building blocks needed to create future electronics and computers. In this talk I will show, as proposed by the Stanford group, that such insulators can be built from common compound semiconductors containing a double-layer of electrons and holes, created by band-gap engineering using molecular beam epitaxy and electrostatic gates. The material supports quantized one dimensional helical edge modes. Quite surprisingly, here we find a superhighway with puzzling twists, for which electron-electron interactions may be responsible. Amazingly, due the interactions between electron and holes, our recent optical and transport experiment confirm that the material can become a superconductor, where the pairing of electron and holes resembles the Cooper pair in ordinary superconductors.
Reference: X. L. Qi,S. C. Zhang, Review of Modern Physics, 83(4), 175 (2010)