Edge and bulk effects in Terahertz photoconductivity of an antidot superlattice - art. no. 045315

We investigate the terahertz (THz) response of a square antidot superlattic e by means of photoconductivity measurements using a Fourier-transform-spec trometer. We detect, spectrally resolved, the cyclotron resonance and the f undamental magnetoplasmon mode of the periodic superlattice. In the dissipa tive transport regime both resonances are observed in the photoresponse. In the adiabatic transport regime, at integer filling factor v=2, only the cy clotron resonance is observed. From this we infer that different mechanisms contribute to converting the absorption of THz radiation into photoconduct ivity in the cyclotron and in the magnetoplasmon resonances. In the dissipa tive transport regime, heating of the electrons via resonant absorption of the THz radiation in the two-dimensional bulk is the main mechanism of phot oconductivity in both resonances. In the case of the cyclotron resonance, a nd especially in the adiabatic transport regime, we find an additional cont ribution to photoconductivity which we interpret as being caused by THz-abs orption-induced backscattering of edge states. The characteristic decay len gth of the magnetoplasmon at the sample edges is about an order of magnitud e larger than the typical width of the edge states in the quantum Hall effe ct. The magnetoplasmon is therefore not able to induce such backscattering of edge states. Thus in the adiabatic transport regime, i.e., when only the edge states contribute to electric conduction, magnetoplasmon excitation d oes not induce a photoconductive signal.