A three dimensional topological insulator (3DTI) is a vastly studied symmetry protected topological phase. Its surface state encloses a three dimensional bulk material and forms a two dimensional Dirac metal with no boundary. In this talk I will describe how this is significant in using topological insulator nano wires and films in order to generate, manipulate, and detect topological effects unique to 3DTI in transport. I will discuss our recent theoretical works studying a p-n junction and a superconducting - normal (SN) interface, and argue that these proposed setups can be used to address two outstanding challenges: the detection of spin-momentum locking in TI and the detection of topological superconductivity in transport experiments. In particular, I will argue that a p-n junction in the quantum Hall regime forms a Mach-Zehnder interferometer based on spin-momentum locking, functioning as a spin-FET with the advantage of separating spin polarized currents on output. I will also discuss how the SN junction can be used in order to detect topological superconductivity in one dimension, and show that in the presence of a quantizing field it can be mapped onto a Majorana interferometer.
