Drift plasma instability near the edge as the origin of the microwave-induced zero-resistance states

We discuss a possible origin of the recently discovered microwave-induced zero-resistance states in very-high-electron-mobility two-dimensional electron systems. We suggest a scenario, in which two mechanisms, bulk and edge, contribute to the measured photosignal. Zero-resistance states are assumed to be due to a drift plasma instability, developing {\em near the edge} of the system under the microwave radiation. The proposed scheme qualitatively agrees with the microwave power, temperature, frequency, magnetic field, and mobility dependencies of the measured photosignal.