Magnetoresistance of a two-dimensional electron gas in a strong periodic potential

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Abstract
We have investigated the magnetoresistance of a two-dimensional electron gas subjected to a periodic potential of variable amplitude. The periodic potential, of period 300 nm, is generated with use of a gate deposited over a layer of patterned resist, and its amplitude is controlled by the gate voltage. At low gate voltages, two series of oscillations periodic in inverse magnetic field are observed. One series, at low magnetic field, is due to the periodic potential and the other is the usual Shubnikov–de Haas oscillations. The application of a small gate voltage generates an increase in the amplitude of the low-field oscillations, followed by a quenching of these oscillations as the gate voltage is increased further. In addition, a low-field positive magnetoresistance is generated, becoming larger with increasing gate voltage. These effects are explained within a semiclassical model of electron transport. Also the Shubnikov–de Haas oscillations quench as the amplitude of the potential increases. This is explained in terms of a broadening of the Landau levels.