Resonating-valence-bond contribution to superconductivity in MgB₂

Abstract

We view MgB₂ as electronically equivalent to (nonstaggered) graphite (B^- layer) that has undergone a zero-gap-semiconductor-to-superconductor phase transition by large c-axis (chemical) pressure due to Mg⁺⁺ layers. Further, like the pπ -bonded planar organic molecules, graphite is a resonating-valence-bond (RVB) system. The RVB's are the "preexisting Cooper pairs" in the "parental" zero-gap semiconducting B^- (graphite) sheets that manifest themselves as a superconducting ground state of the transformed metal. Some consequences are pointed out.