Exchange and correlation in quasi-two-dimensional plasmas in quantum well structures

We present a comparison of experiment and theory of the intersubband excitations in GaAs/AlGaAs quantum well structures. We find that at moderate densities, calculations employing the local spin density approximation for exchange and correlation Coulomb interactions agree well with experimental results. At larger densities there appears to be a discrepancy. We discuss improvements to the theory due to nonlocal exchange and the potential importance of subband nonparabolicity.