Evidence for 2kF electron–electron scattering processes in Coulomb drag

Measurements and calculations of Coulomb drag between two low density, closely spaced, two-dimensional electron systems are reported. The experimentally measured drag exceeds that calculated in the random phase approximation by a significant, and density dependent, factor. Studies of the dependence of the measured drag on the difference in density between the two layers clearly demonstrate that previously ignored q 1⁄4 2kF scattering processes can be very important to the drag at low densities and small layer separations. q 2002 Elsevier Science Ltd. All rights reserved. PACS: 73.40. 2 c; 73.20. 2 r; 73.63.Hs