The effect of screening long-range Coulomb interactions on the metallic   behavior in two-dimensional hole systems
  We have developed a technique utilizing a double quantum well heterostructure that allows us to study the effect of a nearby ground-plane on the metallic behavior in a GaAs two-dimensional hole system (2DHS) in a single sample and measurement cool-down, thereby maintaining a constant disorder potential. In contrast to recent measurements of the effect of ground-plane screening of the long-range Coulomb interaction in the insulating regime, we find surprisingly little effect on the metallic behavior when we change the distance between the 2DHS and the nearby ground-plane. 
L.H. Ho, W.R. Clarke, A.P. Micolich, R. Danneau, O. Klochan, M.Y.   Simmons, A.R. Hamilton, M. Pepper, D.A. Ritchie