The frictional drag force between quantum wells mediated by a fluctuating electromagnetic field

We use the theory of the fluctuating electromagnetic field to calculate the frictional drag force between nearby two- and three-dimensional electron systems. The frictional drag results from coupling via a fluctuating electromagnetic field, and can be considered as the dissipative part of the van der Waals interaction. Unlike in other similar calculations for semiconductor two-dimensional systems, here retardation effects are included. We consider the dependence of the frictional drag force on the temperature T , electron density and separation d . We find that retardation effects become the dominating factor for high electron densities n s , corresponding to thin metallic film, for separation d >10(ε/ n s ) 1/2 , where ε is the dielectric constant, and suggest a new experiment to test the theory. The relation between friction and heat transfer is also briefly commented on.