Angular Momentum and Transition-Metal Superconductivity

The relation between the systematics of superconductivity in the transition metals and the Periodic Table suggests that the transition temperature is chiefly a short-range or "chemical" property. When a local representation of phonons and an angular momentum decomposition of electron wave functions are used, the conventional description of electron-phonon interactions contains chiefly scatterings which change the angular momentum of the electron. This selection rule makes possible the writing of the electron-phonon coupling constant as the quotient of two parameters, each of which is of a chemical nature. This simplification is possible for materials having a high density of d states at the Fermi energy. For such materials, is little affected by the density of states. The theory is compared with the superconducting transition temperatures of transition metals and their alloys.