Electrical Conduction in a Narrow Band. III. Green Function Method

Abstract

The mobility problem of a hole in a narrow s-band is studied from the point of view of the scattering theory on the basis of the Hubbard model. This formalism is appropriate when the spins are almost aligned. In order to extrapolate the results obtained in the case of almost aligned spins to highly disordered states of spins, the Green function technique is introduced. The frequency-dependent conductivity is expressed in terms of the Fourier transform of a retarded Green function. The Green function is calculated by the use of the equation of motion method. Like Hubbard’s third paper, decoupling approximations are made so as to include the effects of spin disorder and those of the motion of electrons. The dependence of the hole mobility on the spin ordering, which was found in a previous paper, is reproduced.