Shape resonances in the interband pairing in nanoscale modulated materials

The Feshbach shape resonance in the interband pairing is shown to provide the mechanism for evading temperature de-coherence effects in macroscopic quantum condensates. This mechanism provides the Tc amplification in particular nanoscale material architectures like superlattices of metallic layers. The Feshbach resonance is reached by tuning the chemical potential to a Van Hove-Lifshitz singularity (vHs) in the electronic energy spectrum associated with the change of the Fermi surface dimensionality of one of the superlattice subbands. The case of light element diborides where Mg is substituted for Al in AlB2 and its similarity with intercalated graphite compounds is discussed