QUASI-CLASSICAL CALCULATION OF MAGNETORESISTANCE OSCILLATIONS OF A 2-DIMENSIONAL ELECTRON-GAS IN AN ANHARMONIC LATERAL SUPERLATTICE POTENTIAL

A classical approach, relating magnetoresistance oscillations of a two-dimensional electron gas (2DEG) in a weak lateral superlattice potential to the guiding-center drift of cyclotron orbits, is extended to periodic potentials of general shape, and justified from the quantum-mechanical Kubo formula. Several reasonable model potentials in a (gate) plane at some distance from the 2DEG are investigated in order to study two competing effects: (1) the suppression of higher harmonics with increasing distance according to Poisson's equation and (2) the relative enhancement of higher harmonics due to the (Thomas-Fermi) screening by the 2DEG itself. An experimental result by Winkler, Kotthaus, and Ploog, showing magnetoresistance oscillations with a rich structure, is closely reproduced by the calculations.