Transport through a band insulator with Rashba spin-orbit coupling: Metal-insulator transition and spin-filtering effects

We calculate the current-voltage characteristics of a one-dimensional band insulator with magnetic field and Rashba spin-orbit coupling which is connected to nonmagnetic leads. Without spin-orbit coupling, we find a complete spin-filtering effect, meaning that the electric transport occurs in one spin channel only. For a large magnetic field which closes the band gap, we show that spin-orbit coupling leads to a transition from metallic to insulating behavior. The oscillations of the different spin components of the current with the length of the transport channel are studied as well.