DETERMINATION OF THE ENERGY-GAP IN THE ACOUSTIC EXCITATION OF A SUPERLATTICE

Strong interlayer correlations generate a long-wavelength energy gap i n the acoustic-excitation spectrum of a superlattice, whose magnitude is determined by the interlayer correlation function. We establish an iterative scheme for the calculation of the latter, starting from the well-known correlation function of the isolated two-dimensional electr on layer. The gap size is displayed as a function of the layer-layer s eparation and of the coupling parameter within a layer.