Effects of defects and dephasing on charge and spin currents in two-dimensional topological insulators

摘要

Using the nonequilibrium Keldysh Green’s function formalism, we investigate the effect of defects on theelectronic structure and transport properties of two-dimensional topological insulators (TI). We demonstratehow the spatial flow of charge changes between the topologically protected edge and bulk states and showthat elastically and inelastically scattering defects that preserve the time-reversal symmetry of the TI lead toqualitatively different effects on the TI’s local electronic structure and its transport properties. Moreover, weshow that the recently predicted ability to create highly spin-polarized currents by breaking the time-reversalsymmetry of the TI viamagnetic defects [J. S.VanDyke and D. K. Morr, Phys. Rev. B 93, 081401 (2016)] is robustagainst the inclusion of a Rashba spin-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 of the induced spin currents changesunder symmetry operations, such as reversal of bias and gate voltages, or spatial reflections. Finally, we showthat the insight into the interplay between topology and symmetry of the magnetic defects can be employed forthe creation of intriguing quantum phenomena, such as highly localized magnetic fields inside the TI.