Schwinger-boson theory of the quantum<i>XXZ</i>model

Abstract

The quantum XXZ model is studied with the help of the Schwinger-boson formalism. The technique is particularly suited to describe the disordered state of low-dimensional quantum magnets. The Hubbard-Stratonovich transformation is employed to construct the saddle-point equations of the theory. The solution of these equations in one dimension yields the dependence of the Haldane gap as a function of the XY anisotropy.