Magnetotransport in lateral superlattices with small-angle impurity scattering: Low-field magnetoresistance

An analytical study of the low-field magnetoresistance of a two-dimensional electron gas subject to a weak periodic modulation is presented. We assume the small-angle impurity scattering characteristic for high-mobility semiconductor heterostructures. It is shown that the condition for existence of the strong low-field magnetoresistance induced by so-called channeled orbits is η3/2ql1, where η and q are the strength and the wave vector of the modulation, and l is the transport mean free path. Under this condition, the amplitude of the magnetoresistance Δρ/ρ scales as η7/2(ql)², while the modulation-induced correction to resistivity at zero magnetic field is of the order of η1/2.