On flux phase and Néel antiferromagnetism in the {\em t}-{\em J}-model}}

Abstract

We reanalyse the mathematical formulation of the flux-state problem within the $t$-$J$ model. The analysis of different parametrizations in the functional representation shows that (i) calculations which take into account constraints for the number of on-site-available states are describing quasiparticles in terms of wrong local statistics, and contain gauge non-invariant objects; (ii) application of the projection technique in the slave-boson(fermion) representation reproduces the correct statistics, and is exactly equivalent to the conventional diagram technique for Hubbard operators; (iii) it is necessary to introduce an additional equation for the effective hopping amplitude for the flux phase. With the technique for Hubbard operators, which allows one to separate charge and spin channels we construct the mean-field equations for a flux-like state which coexists with Néel antiferromagnetism (AF). The formal analysis shows that the equations for real and imaginary parts of the effective hopping amplitude are inconsistent for any $θ\neq 0$ (including $θ=π/4$ which gives flux 1/2). The hopping amplitude is slightly supressed by exchange renormalization. The Néel magnetization $m$ decreases with increasing concentration of holes. The region where antiferromagnetism exists is decreasing