  The lack of some spatial symmetries in planar devices with Rashba spin-orbit
interaction opens the possibility of producing spin polarized electrical
currents in absence of external magnetic field or magnetic impurities. We study
how the direction of the spin polarization of the current is related to spatial
symmetries of the device. As an example of these relations we study numerically
the spin-resolved current in graphene nanoribbons. Different configurations are
explored and analyzed to demonstrate that graphene nanoflakes may be used as
excellent spintronic devices in an all-electrical setup.
