Collective modes in semiconductor double quantum well systems

The interplay of tunneling, Coulomb coupling, and many-body effects on the charge-density (CDE) and spin-density (SDE) excitations of double quantum well systems has been analyzed. For increasing inter-well distances, the system moves from the strong-tunneling regime (one-well limit) towards the zero-tunneling but still strongly Coulomb coupled regime. Important renormalizations due to many-body effects are found in the long-wavelength limit of the CDE and SDE, with the latter exhibing a soft-mode in the intermediate tunneling, low-density regime.