Empirical estimate of a Coulomb matrix element of relevance to superconductivity

Chem. Phys. Lett. 171, p. 161 (1990)

A part of the Coulomb interaction between eletrons in solids, describing a charge density multiplying a hopping term, has recently been proposed to play a fundamental role in superconductivity. We discuss here an empirical estimate of the magnitude of this interaction in a tight-binding model of hydrogen atoms and show that it can be large enough to overcome the density—density Coulomb repulsion and lead to superconductivity.