MAGNETIC SHORT-RANGE ORDER VERSUS LONG-RANGE ORDER IN THE HUBBARD-MODEL

A theory of magnetic short-range order in the paraphase of the one-ban d Hubbard model is presented on the basis of the four-field slave-boso n approach. In the functional-integral scheme the bosonized action, ex pressed in terms of fluctuating local magnetizations and internal magn etic fields, is transformed to an effective Ising model treated in the Bethe-cluster approximation. The theory is evaluated in the saddle-po int approximation including short-range-order effects in a fully self- consistent way. Comparing our results with previous approaches, the gr ound-state phase diagram shows the suppression of antiferromagnetic an d incommensurate spiral long-range-ordered phases in the favor of a pa raphase with short-range order in a wide doping region. Using realisti c values of the on-site Coulomb repulsion for La2-xSrxCuO4, U/t simila r or equal to 8, the critical doping concentration for the destruction of antiferromagnetism is obtained as 3-4%, in agreement with experime nts.