Effects of van der Waals interaction on current drag between quantum wells

There are two different current drag effects between two closely spaced quantum wells; one is dissipative in origin and vanishes at zero temperature; one is due to the change in van der Waals interaction between the wells when the carriers drift relative each other and this effect survives at zero temperature. We concentrate on this second effect in the present work. We use two simplified model-dielectric-functions for a 2D electron gas in the calculation of the van der Waals interaction between the wells. With these functions the interaction is completely determined by the collective excitations; the single-particle continuum has no effect. The results obtained when using these two model-dielectric-functions bracket, and are quite close to, the result from the full calculation using the RPA dielectric function. This fact justifies our use of these model functions in the calculation of the current-drag effect. Since only collective excitations contribute in this treatment we avoid most of the computational complications introduced by the carrier drift.