  The periodic flashing potential has proven to be a powerful tool for
investigating directed atomic currents. By applying the flashing ring-shaped
potential to spin-orbit (SO) coupled, noninteracting Bose-Einstein condensate
(BEC) systems, through photon-assisted tunneling (resonance) techniques, we
demonstrate the generation of tunable alternating (AC) spin and atomic mass
currents that can be precisely controlled in terms of direction and strength.
The underlying mechanism behind this phenomenon is that the flashing potential
supplies enough photons to induce Rabi oscillations and provides momentum
transfer for spin and atomic transport. As the single-particle ground state of
the unperturbed SO-coupled BEC depends on the Raman coupling strength, we
demonstrate how to generate and control AC spin currents in the cases where the
initial state resides in a single-well or double-well phase. In particular, we
realize and explain the mechanism of generating a net AC spin current without
mass current through single-photon resonance processes. It is shown that these
interesting resonance phenomena can be analytically described only by the
simple three-level model, which creates the possibility of transparent controls
of spin dynamics.
