Persistent spin and charge currents and magnification effects in open ring conductors subject to Rashba coupling

We analyze the effect of Rashba spin-orbit coupling and of a local tunnel barrier on the persistent spin and charge currents in a one-dimensional conducting Aharonov-Bohm ring symmetrically coupled to two leads. First, as an important consequence of the spin splitting, it is found that a persistent spin current can be induced, which is not simply proportional to the charge current. Second, a magnification effect of the persistent spin current is shown when one tunes the Fermi energy near the Fano-type antiresonances of the total transmission coefficient governed by the tunnel barrier strength. As an unambiguous signature of spin-orbit coupling, we also show the possibility to produce a persistent pure spin current at the interference zeros of the transmittance. This widens the possibilities of employing mesoscopic conducting rings in phase-coherent spintronics applications.