Coulomb drag between parallel two-dimensional electron systems

The Coulomb contribution to the temperature-dependent rate of momentum transfer, 1/τ_D, between two electron systems in parallel layers is determined by setting up two coupled Boltzmann equations, with the boundary condition that no current flows in the layer where an induced voltage is measured. The effective Coulomb interaction between the layers is determined self-consistently, allowing for the finite thickness of the layers. As T→0, we find that 1/τ_DT² approaches a constant value. At higher temperatures, 1/τ_DT² exhibits a maximum at T=T_max and then decreases as 1/T with increasing temperature. The value of T_max depends on the layer separation d according to T_max∝d^-α, where α≃0.8. The overall magnitude of the calculated 1/τ_D is approximately one-half of the results of a recent experiment, suggesting that other mechanisms of momentum transfer may be important.