ELECTRON-ELECTRON SCATTERING BETWEEN CLOSELY SPACED 2-DIMENSIONAL ELECTRON GASES

Electron-electron interactions between two closely spaced electron gas es can be directly measured by the drag voltage induced in one layer w hen a current is driven through the other. We have used such drag meas urements of GaAs/AlGaAs double quantum wells to probe both the electro nic excitations within each layer and the interlayer Coulomb interacti on. Two contrasting regimes have been explored. First, at high tempera tures we measure an enhanced drag due to the ''antiscreening'' of the coupled plasmon modes - a result which is in good agreement with theor etical predictions. Moreover, we show the importance of many-body corr ections to the plasmon modes, enabling us to test a local-field descri ption of the correlations. Second, drag measurements in the quantum Ha ll regime show more pronounced structure than the Shubnikov-de Haas os cillations; the drag is more sensitive to spin splitting at high filli ng factors and enhances the features seen at low filling factors. We s how that the localised states away from the Landau level centre influe nce the drag. (C) 1998 Elsevier Science B.V. All rights reserved.