Correlation of electrons in a degenerate band

Abstract

The ground-state wavefunction for electrons in a doubly degenerate tight binding band has been investigated by the variational method [M. C. Gutzwiller, Phys. Rev. 137, A1726 (1965). To be referred to as G.III.] The model Hamiltonian consists of a d band with intra-atomic Coulomb interactions between both d states. The expectation values for the approximate ground state are obtained by counting the various configurations as in the earlier work on correlation in a nondegenerate band. Simple criteria are found for the occurrence of ferromagnetism and of a metal-insulator transition, using the approach of Brinkman and Rice in the latter case [W. F. Brinkman and T. M. Rice, Phys. Rev. B 2, 4302 (1970)]. If the density of states is large at the band edge, the ground state of electrons goes from paramagnetic metallic, through an intermediate ferromagnetic metallic state, to insulating as the intra-atomic Coulomb interaction is increased. © 1971 The American Institute of Physics.