Elastic anomalies in superlattices: An explanation

An explanation for the elastic anomalies that have been previously reported in metallic superlattices is presented. The explanation, valid for superlattices with sharp interfaces, makes use of the charge transfer which occurs when two metals with different work functions are in contact. However, contrary to the case of bulk materials where the transferred charge remains localized at the surface, in thin layers the transferred charge is distributed throughout the layer. This change in charge distribution explains the observed anomalies in the lattice constants and in the elastic properties.