Spin and charge rotation invariant approach to the Hubbard model

摘要

We present a slave-boson formulation for the Hubbard model that preserves the spin-rotation and particle-hole symmetries of the paramagnetic phase at half filling. Fermion and boson fields are treated on an equal footing in a functional integral formulation. We show that, while in 2 and 3 dimensions three is a metal-insulator transition as the interaction U increases, in 1 dimension, our approach always gives an insulating state. Short range spin-spin correlations are included at the saddle point level for all values of U, giving a good description of the insulating state. We show that the energy gap in the one-particle spectrum increases from zero as (U -U(sub c))(sup alpha), where U(sub c) is the critical value of the on-site interaction and the exponent alpha is 1 and 1/2 for 2 and 3 dimensions respectively. (author). 12 refs, 6 figs. (Atomindex citation 28:009567)