Controlling the Flow of Spin and Charge in Nanoscopic Topological Insulators

Rapid advances in quantum computation and spin electronics, heralded by the discovery of topological insulators, have been hampered by the inability to control the flow of spin and charge currents at the nanoscale. In this talk, I will demonstrate that such control can be established in nanoscopic two-dimensional topological insulators (TIs) by breaking their time reversal symmetry via magnetic defects. This allows for the emergence of two novel phenomena: the creation of nearly 100% spin-polarized charge currents, and the design of tunable spin diodes. I discuss two mechanisms by which spin-polarized currents can be produced, and show that by superposing them, spin-diodes which are tunable via gate and bias voltage, can be constructed. Finally, I show that a proof-of-concept for the proposed effects can be realized in meso- or macroscale hybrid structures in which TIs interface with both ferro- and antiferromagnets.