Electronic Transport in Topological Insulator Nanostructures

Download or read book Electronic Transport in Topological Insulator Nanostructures written by Seung Sae Hong and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological insulators are states of quantum matter with an insulating gap in the bulk and gapless surface states. The exotic spin nature of the surface electrons, resulting in topological protection from localization, suggests unconventional applications in electronics as well as fundamental scientific interests. While these exotic states have been investigated via surface-sensitive techniques intensively, electronic transport device, crucial to realize topological electronics, has lagged behind due to material challenges in candidate materials. Topological insulator nanostructure is an attractive candidate for device applications, as the size effect and boundary conditions offer a unique way to enhance / tailor the surface electron transport. In this dissertation, we first describe the design principle of topological insulator nanomaterials, with an emphasis on bismuth selenide. Two major material challenges, dominant bulk electron contribution and low surface mobility due to surface oxidation, are discussed and the solutions via nanomaterial synthesis are achieved. Elemental doping and core-shell heterostructures are developed to suppress bulk carriers and to achieve high surface electron mobility. The high electronic mobility allows us to observe Shubnikov-de Haas oscillations originated from the surface Dirac fermions. In addition to the material development, we also investigate transport properties from helical nature of the surface electrons. 1D modes of surface electrons in bismuth selenide nanowire Aharonov-Bohm interferometers is a unique electronic state providing an opportunity to reveal helical spin nature and topological protection via transport. The helical 1D mode, directly observed near the Dirac point under half magnetic flux quantum, is robust against disorder but fragile against a magnetic field breaking time-reversal-symmetry. The newly discovered 1D helical mode is expected to open a new direction to study topological electronics, as well as future applications.