Effects of Defects and Dephasing on Charge and Spin Currents in Two-Dimensional Topological Insulators

摘要

Using the non-equilibrium Keldysh Green's function formalism, we investigatethe effect of defects on the electronic structure and transport properties oftwo-dimensional topological insulators (TI). We demonstrate how the spatialflow of charge changes between the topologically protected edge and bulk statesand show that elastically and inelastically scattering defects that preservethe time reversal symmetry of the TI lead to qualitatively different effects onthe TI's local electronic structure and its transport properties. Moreover, weshow that the recently predicted ability to create highly spin-polarizedcurrents by breaking the time-reversal symmetry of the TI via magnetic defects[Phys. Rev. B 93, 081401 (2016)] is robust against the inclusion of a Rashbaspin-orbit interaction and the effects of dephasing, and remains unaffected bychanges over a wide range of the TI's parameters. We discuss how the sign ofthe induced spin currents changes under symmetry operations, such as reversalof bias and gate voltages, or spatial reflections. Finally, we show that theinsight into the interplay between topology and symmetry of the magneticdefects can be employed for the creation of novel quantum phenomena, such ashighly localized magnetic fields inside the TI.