Density functional theory of superconductivity

Abstract

Abstract We outline a first-principles approach to superconductivity based on a generalized density functional theory that has recently been developed by the present author. Within the generalized density functional framework it can be shown that the atomic nuclei-electron system of an extended solid in its ground state is either a metal or an insulator as long as the Born-Oppenheimer (BO) approximation applies. Any conceivable interaction mechanism of purely electronic character (including interaction with plasmons, magnons, etc.) can never reduce the total energy of the system to below its BO value associated with metallic conductivity or insulating properties. Consequently, a superconducting state whose total energy must necessarily be below that of the metallic state cannot possibly occur within the BO approximation. Hence, in order to bring about superconductivity, electron-phonon interaction is definitely indispensable. We briefly report a generalized-density-functional-based derivation of the gap e...