Surface contribution to Raman scattering from layered superconductors

Generalizing recent work, the Raman-scattering intensity from a semi-infinite superconducting superlattice is calculated taking into account the surface contribution to the density response functions. Our work makes use of the formalism of Jain and Allen developed for normal superlattices. The surface contributions are shown to strongly modify the bulk contribution to the Raman-spectrum line shape below (Formula presented), and also may give rise to additional surface plasmon modes above (Formula presented). The interplay between the bulk and surface contribution is strongly dependent on the momentum transfer (Formula presented) parallel to layers. However, we argue that the scattering cross section for the out-of-phase phase modes (which arise from interlayer Cooper pair tunneling) will not be affected and thus should be the only structure exhibited in the Raman spectrum below (Formula presented) for relatively large (Formula presented). The intensity is small but perhaps observable.