Single electron gating of topological insulators

Abstract: Introducing, observing, and manipulating individual impurities coupled to a host material offers the opportunity to create new device concepts based on single spin and charge states. Because of potential applications in spintronics and magneto-electrics, such an approach would be particularly useful for topological insulators (TI), a recently discovered material class hosting spin-momentum- locked surface states. To make them useful for new technologies, a robust control of their interaction with external perturbations is required. However, traditional approaches such as metal electrodes or doping proved to be problematic and resulted in strong mesoscopic fluctuations making the spin-momentum locking ill-defined. Here, we demonstrate the effective gating of TIs by coupling molecules to their surface which, by using electric fields, allow to dynamically control the interface charge state by adding or removing single electrons. This process creates a robust transconductance bistability resembling a single-electron transistor. Our findings make hybrid molecule/TI interfaces functional elements while at the same time pushing miniaturization at its ultimate limit. This opens a new avenue for all electric-controlled spintronic devices based on these fascinating materials.