Novel Low-Field Magnetoresistance Oscillation in a Unidirectional Lateral Superlattice

Abstract

A two‐dimensional electron gas (2DEG) subjected to a unidirectional potential modulation exhibits so‐called commensurablity oscillations in low magnetic fields, typically B < 0.3 T, which is attributed to geometrical resonances between the cyclotron orbit and the modulation period. We have found a novel type of oscillatory magnetoresistance in short period lateral superlattice samples with weak modulation amplitude. The oscillation is small in amplitude and is superposed on the positive magnetoresistance at lower fields (B < 0.03T). The effect is attributed to a geometrical resonance between the superlattice period and the width of the open orbits created by Bragg reflection from the superlattice. A simple model based on the Fermi surface reconstruction accounts for the positions of the resistance maxima and their electron density dependence. Additional features seen in a sample in which the stripes have periodical notches confirm the model. The experimental requirements for the observability of this resonance effect are elucidated.