Novel microwave-induced zero-resistance states in the two-dimensional electron system

We examine zero resistance states induced by electromagnetic wave excitation in ultra high mobility GaAs/AlGaAs heterostructure devices at low magnetic fields, in the large filling factor limit, below the quantum Hall regime. Zero-resistance states are exhibited about B=(4/5)B_f and B=(4/9)B_f where B_f = 2πfm*/e, m* is the electron effective mass, e is electron charge, and f is the microwave frequency. In this instance, the absence of backscattering appears to be associated with an ordinary Hall effect, unlike the typical quantum Hall situation. The dependence of the effect is reported as a function of electromagnetic wave frequency, the temperature, and other experimental variables.