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 i nteraction; 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, m aking it much easier for inhomogeneous configurations to be stable. Ev en in the uniform liquid phase the presence of a second layer can qual itatively change the nature of the low lying excitation spectrum and l ead to large many-body effects in the spectrum, even at very long wave lengths.