  Persistent, oscillatory charge and spin currents are shown to be driven by a
two-component terahertz laser pulse in a one-dimensional mesoscopic ring with
Rashba-Dresselhaus spin orbit interactions (SOI) linear in the electron
momentum. The characteristic interference effects result from the opposite
precession directions imposed on the electron spin by the two SOI couplings.
The time dependence of the currents is obtained by solving numerically the
equation of motion for the density operator, which is later employed in
calculating statistical averages of quantum operators on few electron
eigenstates. The parameterization of the problem is done in terms of the SOI
coupling constants and of the phase difference between the two laser
components. Our results indicate that the amplitude of the oscillations is
controlled by the relative strength of the two SOI's, while their frequency is
determined by the difference between the excitation energies of the electron
states. Furthermore, the oscillations of the spin current acquire a beating
pattern of higher frequency that we associate with the nutation of the electron
spin between the quantization axes of the two SOI couplings. This phenomenon
disappears at equal SOI strengths, whereby the opposite precessions occur with
the same probability.
