▎ 摘　　要

The lack of some spatial symmetries in planar devices with Rashba spin-orbit interactions opens up the possibility of producing spin polarized electrical currents in the absence of external magnetic fields 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.