Strict site-occupation constraint in two-dimensional Heisenberg models and dynamical mass generation in QED{sub 3} at finite temperature

We study the effect of site occupation in two-dimensional quantum spin systems at finite temperature in a {pi}-flux state description at the mean-field level. We impose each lattice site to be occupied by a single SU(2) spin. This is realized by means of a specific prescription. We consider the low-energy Hamiltonian which is mapped into a QED{sub 3} Lagrangian of spinons. We compare the dynamically generated mass to the one obtained by means of an average site occupation constraint.