Rabi flopping of charge and spin currents generated by ultrafast two-colour photoexcitation of semiconductor quantum wells

Charge and spin currents generated by ultrafast two-colour laser excitation of semiconductor quantum wells are computed using Bloch equations formulated in the basis of k ⋅ p wave functions. The optically induced interband and intraband excitations are treated nonperturbatively for a consistent description of phototransport in the high-excitation regime. The analysis shows that the photoexcited charge and spin currents depend on the amplitudes of the incident ω and 2 ω beams in a highly nonlinear fashion. It is predicted that Rabi flopping should be observable experimentally leading to intensity-dependent changes of the current directions.