Electron Liquid in Double-layer Structures

Two layers of electrons or holes trapped at the adjacent interfaces of a gallium arsenide heterostructure can interact through the Coulomb interaction; this leads to a rich phase diagram of ground states, some of which are inhomogeneous in density. The cause of this is associated with each layer's acting as a polarisable background for the other, making it much easier for inhomogeneous configurations to be stable. Even in the uniform liquid phase the presence of a second layer can qualitatively change the nature of the low lying excitation spectrum and lead to large many-body effects in the spectrum, even at very long wavelengths.