Quantum pumping and rectification effects in Aharonov-Bohm-Casher ring-dot systems

Within the nonequilibrium Green's-function formalism we study the time-dependent transport of charge and spin through a ring-shaped region sequentially coupled to a weakly interacting quantum dot in the presence of an Aharonov-Bohm flux and spin-orbit interaction. The time-dependent modulation of the spin-orbit interaction or of the corresponding Aharonov-Casher flux, together with the modulation of the dot level, induces an electrically pumped spin current at zero bias even in the absence of a charge current. The results beyond the adiabatic regime show that an additional rectification current with an anomalous current-phase relation is generated. We discuss the relevance of such term in connection with recent experiments on out-of-equilibrium quantum dots.