Interplay of dc current and microwaves in the magnetotransport of two-dimensional electron systems

We theoretically study magnetoresistance oscillations in two-dimensional electron systems in the presence of microwaves and a dc electric field. We obtain that the microwave-induced resistance oscillations and zero resistance states are dramatically affected by a dc electric field of increasing intensity. The interplay of both fields produces a plasma wave which oscillates at the frequency of microwaves but with a phase difference of pi radians. This plasma wave interferes with the microwave-induced electronic motion changing gradually the resistance oscillations profile: maxima evolve to minima and vice versa. We introduced in our model anharmonicity corrections to magnetoresistance oscillations in order to explain the peculiar biased profile that experimental results present. The theoretical outcomes are in agreement with experimental evidence.