Possibilities for enhanced electron-phonon interactions and high-T_c superconductivity in engineered bimetallic nanostructured superlattices

We explore theoretically the properties of engineered bimetallic nanostructured superlattices obtainable by embedding a periodic array of nano-clusters of a simple (single band) metal inside another simple metal with a different work function. The exploration is done using a simplified tight-binding model with coulomb interactions included, as well as density functional theory. Taking arrays of Ag clusters of fixed sizes and configurations (when unrelaxed) embedded periodically in an Au matrix as an example, we show that a significant enhancement of electron-phonon interactions ensues, implying possibilities for high-T_c superconductivity. The enhancement stems from a strong hybridization between the interface plasmon oscillations of the electric dipoles that form at the Au-Ag interfaces and the breathing modes of the light Ag atoms caged inside the heavier Au matrix. The interface dipoles form because of the interplay between the mismatch of the local potential seen by the conduction electrons localized in Wannier orbitals at the Ag and Au sites (the Ag sites being slightly repulsive relative to the Au sites) and the long-range coulomb repulsion between electrons occupying these Wannier orbitals.