New approximation in the Gutzwiller method and its application to the problem of itinerant ferromagnetism

Abstract

A new approximation to evaluate physical quantities with Gutzwiller states is proposed. This approximation improves the original Gutzwiller one in the strong-correlation region. In this approximation the Brinkman-Rice–type transition no longer takes place in accord with rigorous results. Consequently, it gives much better energies than the Gutzwiller approximation in the vicinity of the transition point. The method is applied to the problem of itinerant ferromagnetism in sc, bcc, and fcc lattices. It is shown that the domain with the ferromagnetic phase is much narrower in the present approximation than in the Gutzwiller approximation.