Observation of microwave-induced resistance oscillations in a contactless geometry

Abstract

The high-frequency transport of a two-dimensional (2D) electron system was investigated by measuring the rf power transmitted through a pair of emitter/detector $\mathsf{T}$-shaped antennas capacitively coupled to the 2D channel. The frequency range covered amounted to 10--100 MHz. The distinctive feature of such a setup is that neither were Ohmic contacts formed to the electron system, nor were metallic pads deposited on the sample surface. We demonstrate that in such an arrangement the microwave-induced resistance oscillations could be observed in case the sample was additionally excited by a microwave radiation of 60--100 GHz frequencies. The amplitude of the first oscillation is clearly comparable to the amplitude of the Shubnikov--de Haas oscillations resolved at relatively high magnetic fields. Furthermore, introducing Ohmic contacts to the 2D channel or pads deposited directly on the sample surface did not alter significantly the amplitude of the detected microwave-induced resistance oscillations.