Photovoltaic effects in GaAs/AlGaAs quantum Hall devices by optical vortex irradiation

We investigated the photovoltaic effects induced by optical vortex irradiation in a GaAs/AlGaAs two-dimensional electron system under quantum Hall conditions in a high magnetic field at cryogenic temperatures. The absence of electron backscattering with a long energy-relaxation length characterizes the transport of electrons through the edge states in quantum Hall electron systems, where the photocurrent is transported to the electrodes placed sufficiently far away from the illuminated spot. The topological charge m dependence on the photovoltaic effect was investigated using perfect vortices for photovoltage change. A clear difference was observed between the optical vortices with m = ±1 and ±3 and those with m = ±2 and ±4. This suggested that the parity of m has different effects on photoexcitation and/or electron transport through the edge states in the quantum Hall electron system. The observed dependence of the photocurrent on the topological charge is attributed to the eddy current due to interband electron excitation by the optical vortices.