Dynamics of the far-infrared photoresponse in quantum Hall systems

We have studied the time evolution of the far-infrared photoresponse of two-dimensional electron systems in the quantum Hall (QH) regime. We have identified different contributions to the photoresponse by using different sample geometries and by changing the direction of the magnetic field. In general, we have found a fast response (microseconds) related to photoinduced Hall currents, and longer response times (up to some hundreds of milliseconds) related to the photoinduced longitudinal resistance. Both types of the response are present in the bolometric response bound to the flanks of the QH plateau, and in the cyclotron resonance signal bound to the photon energy of the probe radiation. We give a qualitative explanation of our results on the basis of impurity-induced potentials for the localization of excited carriers.