QUANTUM ANTIFERROMAGNET AT FINITE-TEMPERATURE - A GAUGE-FIELD APPROACH

Starting from the CP(N-1) model description of the thermally disordere d phase of the D = 2 quantum antiferromagnet, we examine the interacti on of the Schwinger-boson spin-1/2 mean-field excitations with the gen erated gauge (chirality) fluctuations in the framework of the 1/N expa nsion. This interaction dramatically suppresses the one-particle motio n, but enhances the staggered static susceptibility. This means that t he actual excitations in the system are represented by the collective spin-I excitations, whereas the one-particle excitations disappear fro m the problem. We also show that massive fluctuations of the constrain t field are significant for the susceptibility calculations. A connect ion with the problem of a particle in random magnetic field is discuss ed.