Direct-current control of radiation-induced differential magnetoresistance oscillations in two-dimensional electron systems

Magnetoresistance oscillations in two-dimensional electron systems driven simultaneously by a strong direct current and a microwave irradiation, are analyzed within a unified microscopic scheme treating both excitations on an equal footing. The microwave-induced resistance oscillations are described by a parameter $\epsilon_\omega$ proportional to the radiation frequency, while the dc-induced resistance oscillations are governed by a parameter $\epsilon_j$ proportional to the current density. In the presence of both a microwave radiation and a strong dc, the combined parameter $\epsilon_\omega+\epsilon_j$ is shown to control the main resistance oscillations, in agreement with the recent measurement [Zhang {\it et al.} Phys. Rev. Lett. {\bf 98}, 106804 (2007)]