PLASMON ENHANCEMENT OF COULOMB DRAG IN DOUBLE-QUANTUM-WELL SYSTEMS

We derive an expression for the drag rate (i.e., interlayer momentum t ransfer rate) for carriers in two coupled two-dimensional gases to low est nonvanishing order in the screened interlayer electron-electron in teraction, valid for arbitrary intralayer scattering mechanisms, using the Boltzmann transport equation. We calculate the drag rate for expe rimentally relevant parameters, and show that for moderately high temp eratures (T greater than or similar to 0.2T(F), where T-F is the Fermi temperature) the dynamical screening of the interlayer results in a l arge enhancement of the drag rate due to the presence of coupled plasm on modes. This plasmon enhancement causes the scaled drag rate to have a peak (i) as a function of temperature at T approximate to 0.5T(F), and (ii) as a function of the ratio of densities of the carriers in th e two layers when their Fermi velocities are equal. We also show that the drag rate can be significantly affected by the intralayer scatteri ng mechanisms; in particular, the drag rate changes approximately by a factor of 2 when the dopant-layer modulation doped structures are mov ed in from 400 to 100 Angstrom.