References

The infinite U Hubbard model is investigated to envisage the derivation of effective action for spin variables that could eventually describe the Nagaoka’s phase for itinerant magnetism. For this, the su(2|1) coherent-state path integral approach is considered and the fermionic variables (representing holes/vacancies) are integrated out. This formalism naturally incorporates the local non double occupancy constraint. The leading term of the effective action in the limit of the weak hopping expansion (longwavelength) corresponds to a ferromagnetic (FM) (Nagaoka’s type) term, as shown previously by us (Kochetov, Braghin, Ferraz). However, in the thermo-dynamical limit the whole effective action disappears unless very particular limits of some of the parameters are considered. Three of these limits, corresponding in fact to different scenarios of the system, are shown: (i) for one particular (limiting) value of the chemical potential (µ), by means of a kind of ”scaling ” of µ(T) with the temperature T; (ii) for the hole hopping between two different sublattices with different averaged hole concentrations (or, equivalently, different time phases) that can modify the magnetic ordering, and (iii) con-sidering a condensation of a specific spinon configuration. Calculations using slave fermion and doped carrie