Electron correlation and charge transfer instability in bilayered two-dimensional electron gas

We prove that the predicted charge transfer state in symmetric bilayers of two-dimensional electron gases is always unstable at zero bias voltage, due to interlayer interactions and/or tunneling. This is most easily seen by resorting to a pseudospin formalism and considering coherent states obtained from the charge transfer state through rotations of the pseudospins. Evidently, the charge transfer state is stabilized by a sufficiently strong gate voltage, as found in recent experiments. We show that a simple model, in which the layers are strictly two-dimensional, is able to account quantitatively for such experimental findings, when correlation is properly included.