Ladder approximation in coupled quantum-well systems

We study the contact values of the interlayer pair-correlation function in electron-electron and electron-hole double-layer systems. For this purpose the ladder approximation as generalized to multicomponent systems is used. The ladder approximation yields positive values for the interlayer gee(0) and geh(0) for all values of the density parameter rs and layer spacing d. This allows us to infer possible instabilities in the system more reliably compared to other approaches. We also investigate the effects of quantum-well width and screening on the interlayer pair-correlation functions.