Charge and spin current in a quasi-one-dimensional quantum wire with spin-orbit coupling

We show that Rashba spin-orbit coupling may result in an energy gap in the spectrum of electrons in a two-mode quantum wire if a suitable confining potential is chosen. This leads to a dip in the conductance and a spike in the spin current at the corresponding position of the Fermi level. Therefore one may control the charge and spin currents by means of electrostatic gates without using a magnetic field or magnetic materials.