  We investigate theoretically the effect of spatial asymmetry on the energy
and momentum transfer rates in a double-quantum-well system using balance
equation approach. Our study is limited to the linear regime where the applied
electric field is sufficiently weak. We calculate the screened potential by
using the random phase approximation and Hubbard approximation for the cases of
high and low electron densities, respectively. Our numerical results predict
that the spatial asymmetry affects considerably both the energy transfer and
drag rates as a result of changes in plasmon modes. Also, we find that the
spatial asymmetry effect disappears at lower temperatures by inclusion the
short-range interaction.
