Lateral transport studies of coupled electron gases

Lateral transport studies of double quantum wells have led to the observation of large nonlinear transconductances. This can arise from mobility modulation and resonant tunnelling. In this paper, by measuring samples with different coupling, we are able to contrast and compare the two effects. The mobility dependence of the two effects is found to be different and with appropriate choice of mobilities we are able to control the size of the nonlinearities. We are also able to demonstrate that for the weakly coupled devices a current switch can be produced exhibiting over 50% current transfer. Parallel magnetic field studies have also been performed on systems with varying degrees of coupling. In all cases this produces a shift in the relative position of the Fermi surfaces which alters the coupling. This leads to magnetoresistance changes which can be especially large for the weakly coupled systems. Additional features are seen for strongly coupled systems due to distortions of the Fermi surface and the appearance of an anisotropy in the conduction.