Classical and Quantum Motion in Lateral Superlattices

We have studied the magnetoresistance of a two-dimensional electron gas (2DEG) subjected to a periodic potential created using electrostatic gates. Periods vary between 100 nm and 500 nm. The detailed behaviour of the magnetoresistance, which includes a positive contribution at very low magnetic fields and oscillatory behaviour periodic in 1/ B at higher fields, is explained successfully within a semi-classical framework. The dependence of the magnetoresistance on amplitude of potential and temperature is explained quantitatively. The limits to the validity of the semi-classical approach are derived. By rotating the sample we are able to alter the magnetoresistance in an anisotropic fashion depending on the relative direction between the equipotentials and the axis of rotation. This is interpreted in terms of the in-plane magnetic field allowing the zero-point motion in the confinement direction to be observed in the plane of the 2DEG.